Benzoaza-15-crown-5 ethers: Synthesis, structure, and complex formation with metal and ethylammonium ions

Russian Chemical Bulletin, International Edition, Vol. 58, No. 5, pp. 978—1001, May, 2009

978

Benzoazaꢀ15ꢀcrownꢀ5 ethers: synthesis, structure, and complex formation

with metal and ethylammonium ions

A. I. Vedernikov,^aS. N. Dmitrieva,^aL. G. Kuz´mina,^bN. A. Kurchavov,^a

Yu. A. Strelenko,^cJ. A. K. Howard,^dand S. P. Gromov^a

^aPhotochemistry Center, Russian Academy of Sciences,

7A ul. Novatorov, 119421 Moscow, Russian Federation.

Fax: +7 (495) 936 1255. Eꢀmail: gromov@photonics.ru

^bN. S. Kurnakov Institute of General and Inorganic Chemistry, Russian Academy of Sciences,

31 Leninsky prosp., 119991 Moscow, Russian Federation.

Fax: +7 (495) 954 1279

^cN. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences,

47 Leninsky prosp., 119991 Moscow, Russian Federation.

Fax: +7 (499) 135 5328

^dDepartment of Chemistry, University of Durham, South Road, Durham DH1 3LE, UK

Benzoazaꢀ15ꢀcrownꢀ5 ethers containing one or two nitrogen atoms in different positions

of the macrocycle and bearing different substituents at these atoms were synthesized. The

structures of azacrown ethers and their metal complexes were studied by Xꢀray diffraction.

The stability constants of the complexes of azacrown ethers with Na⁺, Ca²⁺, Ba²⁺, Ag⁺, Pb²⁺

,

1

+

and EtNH₃ions were determined by H NMR titration in MeCNꢀd₃. In free benzoazacrown

ethers containing secondary nitrogen atoms bound to the benzene ring, as well as in Nꢀacetyl

derivatives, the N atoms are sp²ꢀhybridized and have a planar geometry. The nitrogen lone

pairs on the p orbitals are efficiently conjugated to the benzene ring or the carbonyl fragment of

the acetyl group, which is unfavorable for the complex formation. In addition, the formation

of complexes with benzoazacrown ethers containing secondary nitrogen atoms is hindered

because the hydrogen atoms of the NH groups are directed to the center of the macrocyclic

cavity. In benzoazacrown ethers bearing Nꢀalkyl substituents or secondary nitrogen atoms

distant from the benzene ring, the N atoms show a substantial contribution of the sp³ꢀhybridꢀ

ized state and have a pronounced pyramidal configuration, which promotes the complex

formation. The lead and calcium cations form the most stable complexes due to the high

affinity of Pb²⁺ions for O,Nꢀcontaining ligands, a high charge density on these ions, and the

better correspondence of the cavity size of the 15ꢀmembered macrocycles to the diameter of

the Ca²⁺ion. An increase in the stability of the complexes is observed mainly in going from

monoazacrown ethers to diazacrown ethers containing identical substituents at the N atoms

and in the following series of substituents: C(O)Me < H < Me < CH₂CO₂Et. In the case of

the CH₂CO₂Et substituents, the carbonyl oxygen atom is also involved in the coordination to

the cation. The characteristic features of the complexing ability of Nꢀalkylbenzomonoazaꢀ

15ꢀcrownꢀ5 ethers bearing the nitrogen atom conjugated to the benzene ring show that macroꢀ

cyclic ligands having this structure are promising as selective and efficient complexing agents

for metal cations.

Key words: benzoazacrown ethers, complex formation, metal cations, ethylammonium

1

ion, stability constants, Xꢀray diffraction study, H NMR spectroscopy.

The discovery of cyclic polyethers in the late 1960s¹

branes, in ionꢀselective electrodes, as phaseꢀtransfer cataꢀ

lysts, etc.²The replacement of one or several oxygen

atoms in crown ethers by nitrogen atoms leads to a change

in the selectivity with respect to metal ions and, as a

rule, to an increase in stability of the complexes. The

synthesis of azacrown compounds was described in detail

in reviews.^3—5

has stimulated the vigorous development of the chemistry

of macrocyclic ligands due to the pronounced ability of

crown ethers to selectively bind metal and ammonium

cations. This ability lied at the basis of the use of these

compounds for the determination, extraction, and sepaꢀ

ration of metal cations, in the ion transport through memꢀ

Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 954—976, May, 2009.

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

979

Azacrown ethers containing the nitrogen atom conjuꢀ

gated to the benzene ring are of particular interest because

this structural feature allows the use of these compounds

for the design of molecular optical sensors with a substanꢀ

tial shift of absorption and/or fluorescence and a stronger

optical response to the complex formation compared to

the related compounds containing the O atom conjugated

to a chromophoric moiety. Chromogenic Nꢀphenylꢀ

azacrown ethers (see, for example, Refs 6—8) have been

studied in most detail. However, these compounds have a

substantial drawback in that the stability constants of their

complexes with metal cations are low. This is due to the

efficient conjugation of the nitrogen lone pair of phenylꢀ

azacrown ethers to chromophores, which hinders the

switching of this lone pair to the formation of a coordiꢀ

nation bond with a cation, resulting in the complex

formation. The efficient conjugation leads to sp²ꢀhybridꢀ

ization of the nitrogen atom due to which the N atom

and three substituents at this atom are in the same plane,

resulting in the additional hindrance to the formation

of complexes with metal and ammonium cations, which

requires considerable conformational rearrangements of

the macroheterocycle.⁹

ligands 1a—f are preorganized to form inclusion comꢀ

plexes.

1: X = CHO (a—c), NO₂(d—f); n = 0 (a, d), 1 (b, e), 2 (c, f)

2, 3: X = H (a), CHO (b), NO₂(c)

A quantitative comparison of the complexation

properties of benzoazacrown ethers depending on the

number and positions of nitrogen atoms in the macrocycle

and the estimation of the influence of the substituents at

the nitrogen atoms on these properties are of considerable

interest. These data can provide insight into the most

promising macrocyclic ligands for the use of their strucꢀ

tural fragments in efficient and selective molecular

chemosensors with a strong optical response to the forꢀ

mation of complexes with metal and ammonium cations.

In the present study, we report the synthesis and strucꢀ

tural features of benzoazaꢀ15ꢀcrownꢀ5 ethers 4—7 conꢀ

taining the unsubstituted benzene ring and their metal

complexes, which were characterized by Xꢀray diffracꢀ

Benzannulated derivatives of azacrown ethers can

have substantial advantages as complexing agents over

Nꢀphenylazacrown ethers due to the higher conformaꢀ

tional rigidity of the macrocycle and the possibility of a

weakening of the conjugation of the nitrogen lone pair to

the benzene ring for steric reasons. However, benzoazaꢀ

crown ethers containing the nitrogen atom bound to the

benzene ring are poorly known in spite of their relatively

simple structures.⁵

Earlier, we have developed¹⁰a procedure for the

synthesis of formyl and nitro derivatives of Nꢀmethylꢀ

benzoazacrown ethers 1a—f by the stepwise transformaꢀ

tion of the macrocycle of benzocrown ethers 2 (for

example, of 2b,c) and have shown^11—13that these comꢀ

pounds have the ability to efficiently bind calcium

cations. This ability is comparable to that of benzocrown

ethers and is substantially higher than the binding ability

of Nꢀphenylazacrown ethers containing the macrocycle

of the same size and bearing the same substituent in the

benzene ring. The high binding ability of benzoazacrown

ethers 1a—f is determined by steric interactions between

the methyl and methylene groups at the nitrogen atom

containing an alkoxy substituent in the ortho position.

This leads to a partial decrease in the conjugation of

the lone pair of this N atom to the benzene ring and the

pronounced pyramidal geometry of the N atom favorable

for the involvement of the nitrogen lone pair in the coorꢀ

dination bond with metal cations. The multidentate bindꢀ

ing of metal cations is additionally facilitated by the fact

that macroheterocycle 1 prefers to have a crown conforꢀ

mation, in which the lone pairs of most of heteroatoms

are directed to the center of the macrocyclic cavity, i.e.,

4—7: R = H (a), Me (b), C(O)Me (c), CH₂CO₂Et (d)

5: R´ = H (a, c), Me (b)

980

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

Scheme 1

tion. The structures and the complexing ability of these

compounds with respect to metal and ethylammonium

cations were studied by ¹H NMR spectroscopy. For comꢀ

parison, we determined the corresponding characteristics

of model compounds 2a and 3a with the same size of the

macrocycle and of some related compounds.

Results and Discussion

Synthesis of benzoazacrown ethers. Benzoazacrown

ethers 4a and 5a were synthesized by the condensation

of 2ꢀaminophenol or oꢀphenylenediamine with halogen

derivatives of tetraethylene glycol in the presence of bases

under high dilution conditions to prevent the formation

of oligomerization products (Scheme 1). Only trace

amounts of the target product 4a were obtained (in 1.6%

yield) upon heating of a mixture of 2ꢀaminophenol and

1,11ꢀdiiodoꢀ3,6,9ꢀtrioxaundecane in MeCN in the presꢀ

ence of Na₂CO₃. The careful chromatographic separation

of the reaction mixture allowed us to isolate also a byꢀ

product, which proved to be the oꢀhydroxy derivative of

Nꢀphenylazaꢀ12ꢀcrownꢀ4 ether 8 (in 2.8% yield). Apparꢀ

ently, under the conditions of the synthesis, the basicity

of Na₂CO₃is too low to provide the efficient deprotonation

of the hydroxy group of 2ꢀaminophenol or the interꢀ

mediate aza podand, which is the openꢀchain analog of

the azacrown ether. This results in the strong resinification

of the reaction mixture and in the partial closure of the

aza podand to form the more strained 12ꢀmembered ring

8. On the contrary, the condensation of oꢀphenylenediꢀ

amine with 1,11ꢀdiiodoꢀ3,6,9ꢀtrioxaundecane under these

conditions afforded benzodiazacrown ether 5a in 25%

yield. This fact confirms the conclusion that the amino

group in the aniline derivative is relatively reactive toward

diiodoalkane. Benzomonoazacrown ether 4a was syntheꢀ

sized in 8% yield by the condensation of 2ꢀaminophenol

with 1,11ꢀdichloroꢀ3,6,9ꢀtrioxaundecane in an water—

butanol solution in the presence of NaOH. It should be

noted that compounds 4a, 5a, and 8 have been described

previously;^14—17however, the yields of these products have

not been reported or their yields were lower than those

obtained in our work.

X = O (4a), NH (5a); R = H (7a), Me (7b); Y = Cl, I

The synthesis of compounds 4b—d, 5b,c, 6c,d, and

7c,d is presented in Scheme 2. The Nꢀmethyl derivatives

of azacrown ethers 4b and 5b were synthesized by the

reactions of compounds 4a and 5a, respectively, with

methyl iodide in the presence of NaH in dry THF. The

methylation of diamine 5a afforded double alkylation

product 5b in almost quantitative yield. The monoꢀ

Nꢀmethylation product of compound 5a was not detected

by TLC monitoring of the course of the reaction. Apparꢀ

ently, this intermediate is more reactive toward MeI than

the starting compound 5a due probably to the influence of

the tertiary amino group in the ortho position with respect

to the NH group. It should be noted that N,N´ꢀdimethyl

derivative 5b can be theoretically formed as trans and/or

cis isomers, in which the methyl substituents are located

on opposite sides or on the same side of the macrocycle,

respectively. Under ambient conditions, the exchange beꢀ

tween the isomers of 5b is unlikely due to steric hindrance

to the rotation of the N(Me)CH₂group about the N—C_Ar

bond caused by the second bulky N(Me)CH₂group in the

Benzomonoazacrown ether 6a and its Nꢀmethyl

derivative 6b are commercially available products. The

synthesis of benzodiazacrown ether 7a by the reduction

of the corresponding macrocyclic diamide was docuꢀ

mented.¹⁸N,N´ꢀDimethyl derivative 7b has been synꢀ

thesized previously by sonication of compound 7a with

methyl iodide¹⁹or by the reduction of the corresponding

bisurethane.²⁰In the present study, we suggest the syntheꢀ

sis of compounds 7a,b by the condensation of two acyclic

precursors, viz., 1,2ꢀbis(2ꢀiodoethoxy)benzene and terꢀ

minal diamines (see Scheme 1), by analogy with the

method developed in our earlier work for the synthesis of

formyl derivatives of benzodiazacrown ethers.²¹

1

ortho position. The H NMR spectroscopic data provide

evidence that compound 5b is formed as one isomer

because the spectra of the free ligand and its complexes

with metal cations show only one set of signals for protons

(except for the complexes with Pb²⁺due to the slow

exchange; see below). The cis structure of this isomer was

established by the Xꢀray diffraction study of the complex

of compound 5b with barium perchlorate.

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

981

Scheme 2

X = O (4b,c), NMe (5b), NH (5c)

The Nꢀacetyl derivatives of benzoazacrown ethers

4c—7c were synthesized by heating the corresponding

secondary amines in acetic anhydride. In the case of

benzodiazacrown ether 5a, the acylation was carried out

in benzene. This allowed us to introduce only one Nꢀacetyl

group due apparently to considerable steric hindrance to

the acylation of the NH group in crown ether 5c caused

by the bulky N(Ac)CH₂moiety in the ortho position.

Compounds 4a, 6a, and 7a were modified by ester side

groups to form azacrown ethers 4d, 6d, and 7d, respecꢀ

tively, through the Nꢀalkylation with ethyl bromoacetate

in the presence of a base.

Xꢀray diffraction study. Azacrown ethers 4a,c, 5a,c,

6a—c, 7a, and 8 were prepared as single crystals and were

studied by Xꢀray diffraction. The structures of these comꢀ

pounds are shown in Figs 1 and 2. For convenience of

the comparison of the geometric parameters, we used the

same atomic numbering scheme that differs from the

IUPAC nomenclature. The asymmetric units of 4a and

6a contain two independent molecules of azacrown ethers,

which differ in the conformation of the polyether chain.

Since the structures of most of the compounds under

study were determined with high accuracy, their main

geometric parameters can be compared. The exception is

compound 6a, whose crystals are characterized by high

mosaicity. However, the geometric characteristics of

the latter compound show the same tendencies as those

observed for the other structures. It should be noted

that the crystallographic parameters of compounds 5a

and 7a determined at 240 K and at room temperature,

respectively, have been described previously.^22,23The

structural motifs of these compounds determined in

the present study are similar to those described in the

literature; however, we cooled the single crystals to

982

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

O(5)

C(15)

C(16)

C(8´)

C(14)

C(13)

C(7´)

C(9´)

C(2)

C(3)

C(1)

N(1)

C(12)

C(5´)

O(6)

O(4)

C(6´)

O(3)

O(5)

O(1)

C(11)

C(10´)

C(11´)

C(4´)

C(3´)

C(4)

C(6)

O(7)

O(2)

C(5)

H(2)

N(2)

C(1´)

C(7)

C(10)

O(8)

C(8)

C(9)

C(2´)

C(12´)

C(14´)

O(4)

4c

C(13´)

C(13)

C(12)

C(11)

C(13)

O(3)

C(2)

C(6)

C(14)

H(1)

O(2)

C(1)

N(1)

O(3)

C(14)

C(3)

C(4)

C(11)

C(16)

C(6)

O(1)

C(1)

C(2)

C(3)

O(2)

C(5)

C(7)

N(2)

H(2)

C(9)

C(8)

C(10)

C(15)

C(4)

O(4)

C(10)

O(1)

C(9)

N(1)

C(5)

4a

C(7)

C(8)

5c

C(13)

C(14)

C(4)

C(3)

C(5)

O(3)

C(12)

C(2)

C(1)

C(3)

C(11)

O(2)

N(2)

C(6)

H(2)

O(1)

C(1)

C(2)

C(4)

C(12)

C(11)

H(1)

N(1)

C(13)

C(10)

C(6)

C(5)

O(3)

O(1)

H(1)

N(1)

C(14)

O(4)

C(7)

O(2)

C(9)

C(10)

C(8)

C(7)

C(9)

C(8)

5a

8

Fig. 1. Molecular structures of compounds 4a (two independent molecules), 4c, 5a,c, and 8. Thermal ellipsoids are drawn at the 50%

probability level. The hydrogen bonds are indicated by dashed lines.

120 K with the aim of improving the accuracy of Xꢀray

diffraction data.

In the benzene rings of all benzoazacrown ethers, the

C(1)—C(6) bond shared by the rings of the bicyclic system

is somewhat elongated (the average value is 1.410(3) Å),

whereas the opposite C(3)—C(4) bond is the shortest

one (the average value is 1.369(4) Å) compared to the

other bonds of the benzene ring (the average values are

1.390(3)—1.397(3) Å). This bond length distribution

undoubtedly reflects the steric repulsion between the ortho

Benzoazacrown ethers and their complexes

O(7)

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

983

C(12´)

C(11´)

C(14´)

C(13´)

N(2)

C(2´)

C(1´)

C(3´)

O(2)

C(7)

H(2)

O(6)

O(8)

O(5)

C(6´)

C(9)

N(1)

C(8)

C(5)

C(10´)

C(9´)

C(6)

C(1)

C(4´)

C(3)

C(8´)

C(10)

C(5´)

C(7´)

C(15)

O(1)

O(4)

C(4)

C(11)

O(3)

C(2)

C(13)

C(14)

C(3)

C(2)

C(4)

C(1)

C(12)

O(3)

C(12)

C(11)

C(14)

O(4)

C(13)

C(5)

H(1)

N(1)

C(6)

C(7)

O(1)

6b

C(10)

O(2)

C(8)

C(9)

6a

O(1W)

H(2W)

H(1W)

C(8)

N(1)

C(9)

C(10)

C(7)

C(6)

C(5)

C(7)

C(6)

C(9)

C(5)

O(2)

O(1)

H(1)

C(10)

C(15)

C(4)

O(1)

O(3)

O(2)

C(4)

C(3)

C(11)

C(16)

O(5)

N(1)

H(2)

N(2)

C(1)

C(2)

O(4)

C(11)

C(3)

C(1)

C(2)

C(12)

O(3)

C(14)

C(13)

C(14)

C(13)

6c

7a•H₂O

Fig. 2. Molecular structures of compounds 6a (two independent molecules), 6b,c, and 7a•H₂O. Thermal ellipsoids are drawn at the

50% probability level. The hydrogen bonds are indicated by dashed lines.

substituents at the C(1) and C(6) atoms, which should

also lead to an increase in the C(6)—C(1)—N/O and

C(1)—C(6)—N/O bond angles and, consequently, to a

decrease in the C(2)—C(1)—N/O and C(5)—C(6)—N/O

bond angles. However, we observed the opposite situaꢀ

tion. Thus, the bond angles at the C(1) and C(6) atoms

exocyclic with respect to the benzene ring show a proꢀ

nounced tendency to an increase in the case of the

C(2)—C(1)—N/O and C(5)—C(6)—N/O bond angles (on

the average, by 125.0(2)°) and to a decrease in the case of

the C(6)—C(1)—N/O and C(1)—C(6)—N/O bond angles

(on the average, by 115.3(2)°) for compounds 4a, 6a—c,

and 7a (Table 1). This deformation of the bond angles

compared to the ideal value (120°) characteristic of most

of benzocrown ethers results in a decrease in the distance

between the N and/or O atoms in the ortho positions

and is attributed to the fact that the lone pairs of these

heteroatoms on the p orbitals are efficiently conjugated

to the benzene ring.^24,25The conjugation is favored also

by the conformation of the C(2)—C(1)—N/O—C and

C(5)—C(6)—N/O—C fragments, such that these torsion

angles are relatively small (–20.5—17.4°), i.e., are close

to zero, which is the ideal value for the conjugation. The

presence of conjugation is evidenced also by the predomiꢀ

nantly sp²ꢀhybridized state of the N and O atoms characꢀ

terized by the bond angles at these atoms close to 120°, as

984

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

well as by shortened N/O—C_Arbonds compared to

N/O—C_Alkbonds. An analogous, but a less pronounced

tendency for the deviation of the aboveꢀmentioned

parameters from the ideal values is observed in diazacrown

ether 5a due apparently to the steric interaction between

the hydrogen atoms of two NH groups in the ortho

positions. In amide 4c and phenylazacrown ether 8, the

deviations of the bond angles from the ideal value (120°)

are observed only for one of the carbon atoms of the

benzene ring (C(6) in 4c and C(1) in 8). In amide 4c,

the O(1) atom bound to the C(6) atom is evidently conjuꢀ

gated to the benzene ring, which is favored by the small

C(5)—C(6)—O(1)—C(7) torsion angle (–8.0°). The

amide N(1) atom in compound 4c is sp²ꢀhybridized, and

the sum of the bond angles at this atom is 360.0(1)°.

However, the N(1) atom is involved in the conjugation

not to the benzene ring but to the carbonyl group. Thus,

the AcNC₂fragment is planar, and the dihedral angle

between this plane and the plane of the benzene ring is

80.0°. The fact that the nitrogen atom in compound 4c

is not involved in the conjugation to the benzene ring is

evidenced also by a considerable elongation of the

N—C_Arbond compared to the corresponding bonds

in the other azacrown ethers. The similar geometry is

observed also in amide 5c, in which the angle between the

planes of the AcN(1)C₂fragment and the benzene ring is

82.0°. The second nitrogen atom in amide 5c is efficiently

conjugated to the benzene ring, which is seen from

the geometric characteristics of the N(2) atom and its

environment (see Table 1). The AcNC₂fragment in amide

6c, in which the nitrogen atom is distant from the benꢀ

zene ring, is planar. The latter fact is indicative of the

presence of efficient conjugation in this fragment. In

the other azacrown ethers containing nitrogen atoms

distant from the benzene rings (6a,b and 7a), these nitroꢀ

gen atoms have a pronounced pyramidal bond configuraꢀ

tion. The sums of the bond angles at the nitrogen atoms

are close to the value typical of the ideal sp³ꢀhybridized

state (328.4°).

The hydrogen atoms of the NH groups in compounds

4a, 5a,c, 6a, and 7a are directed to the center of the

macrocyclic cavity and apparently form predominantly

intramolecular hydrogen bonds with the nitrogen and

oxygen atoms of the macrocycles. The hydrogen bond

parameters are as follows: in 4a the N(1)—H...O(1),

N(1)—H...O(4), N(2)—H...O(5), and N(2)—H...O(8)

distances are 2.23, 2.46, 2.24, and 2.46 Å, respectively,

and the angles at the H atoms are 105—108°; in 5a the

N(1)—H...O(1) and N(2)—H...N(1) distances are 2.33

and 2.39 Å, respectively, and the corresponding angles

Table 1. Selected bond lengths (d), bond angles (ω), torsion angles (ϕ), and the sums of the bond angles at the N atoms (Σ_ω) in

azacrown ethers 4a,c, 5a,c, 6a—c, 7a•H₂O, and 8

Parameter

4a^a

4c

5a

5c

6a^a

6b

6c

7a•H₂O

8

Bond

d/Å

C(1)—N/O

1.387(2), 1.437(2) 1.386(1) 1.365(2) 1.394(5), 1.363(1) 1.369(2) 1.369(1) 1.430(2)

1.378(2) 1.359(5)

1.372(2), 1.360(2) 1.403(1) 1.443(2) 1.354(5), 1.359(1) 1.371(2) 1.367(1) 1.361(2)

C(6)—N/O

1.375(2)

1.396(5)

Angle

ω/deg

C(2)—C(1)—N/O

124.0(2), 119.8(1) 122.1(1) 122.8(1) 125.0(4), 125.1(1) 125.7(1) 124.2(1) 124.2(1)

124.0(2) 125.9(4)

116.7(2), 120.0(1) 119.4(1) 120.3(1) 115.2(4), 114.7(1) 114.5(1) 116.3(1) 116.3(1)

117.0(2) 115.0(4)

115.1(1), 115.6(1) 117.7(1) 120.0(1) 115.2(4), 114.1(1) 115.1(1) 115.6(1) 120.4(1)

114.6(2) 115.5(4)

124.8(2), 125.2(1) 123.0(1) 118.8(1) 126.0(4), 126.1(1) 125.0(1) 124.8(1) 119.4(2)

125.1(2) 124.6(5)

119.8(1), 118.2(1) 122.7(1) 125.0(1) 116.2(3), 117.7(1) 117.9(1) 116.3(1) 113.9(1),

C(6)—C(1)—N/O

C(1)—C(6)—N/O

C(5)—C(6)—N/O

b

C(1)—N/O—C_mc

C(6)—N/O—C_mc

118.9(1)

118.1(4)

116.1(1),

—

118.6(1), 117.7(1) 119.3(1) 119.6(1) 117.7(4), 118.6(1) 117.2(1) 117.9(1)

118.1(1)

349(2),

348(2),

115.8(3)

360.0(1) 340.7(9), 358.4(1), 335(3),

355.6(9), 359.0(13) 320(5),

ϕ/deg

Σ_ω/deg

Angle

330.9(1) 359.5(1) 328.6(9), 345.1(1)

328.7(9),

C(2)—C(1)—N/O—C_mc–16.5,

–20.0

80.5

30.2

–2.8

–2.6,

–14.1

17.4,

0.8

–13.5

7.3

5.3

–19.6

13.3

–53.2,

84.0

—

C(5)—C(6)—N/O—C_mc

8.1,

–8.0

–11.2

–76.1

–20.5

16.7

^aFor two independent molecules.

^bC_mcis the C atom of the macrocycle.

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

985

are 112 and 106°; in 5c the N(2)—H...O(1) distance is

2.33 Å and the angle is 149°; in 6a the N(1)—H...O(2)/O(3)

and N(2)—H...O(6)/O(7) distances are in the range of

2.51—2.62 Å, and the angles are in the range of 98—102°;

in 7a the N(1)—H...O(1)/O(2) and N(2)—H...O(2)/O(3)

distances are in the range of 2.31—2.37 Å, and the angles

are in the range of 109—111°. Evidently, the aboveꢀgiven

geometric parameters of most of the hydrogen bonds, in

particular, the angles at the H atoms, are not optimum for

this type of interactions in the case of formation of one

hydrogen bond; however, the angles at the H atoms in

systems with a bifurcated hydrogen bond can be close

to those observed in the compounds under consideration.

In the crystal structures of most of the benzoazacrown

ethers under study with an intramolecular hydrogen bond,

the macrocycle adopts a crownꢀlike conformation, which

allows the maximum number of NH...heteroatom interꢀ

actions to be formed, thus ensuring the stabilization of

this conformation of the ligand.

C(13)—C(14) is disordered over two sites with occupanꢀ

cies of 0.90 : 0.10. In one independent complex of 5b

with Ba(ClO₄)₂, the coordination sphere of the Ba(2) ion

involves the solvent water molecule H₂O(1W). The comꢀ

mon structural feature of the crystalline complexes of

benzoazaꢀ15ꢀcrownꢀ5 ethers with Ba(ClO₄)₂is that they

form dinuclear systems consisting of two metal complexes.

In the dinuclear systems, two of the four perchlorate

anions serve as bridges and link two barium cations through

the oxygen atoms. The dinuclear systems consisting of

two independent complexes are exemplified by the comꢀ

plexes 5b•Ba(ClO₄)₂•0.5H₂O and 6d•Ba(ClO₄)₂(see

Fig. 3). In the other cases, the dinuclear systems are

centrosymmetric. Hence, only perchlorate anions, which

are involved in the coordination spheres of the indepenꢀ

dent Ba cations, are shown. The coordination numbers of

the barium cations in the complexes vary from 9 to 11.

The coordination polyhedra of these cations are irregular,

which is typical of Ba²⁺cations.

In compound 8 containing the hydroxy group in

the ortho position of the benzene ring with respect to the

azamacrocycle, there is also the intramolecular bifurcated

hydrogen bond characterized by the O(1)—H...O(2) and

O(1)—H...N(1) distances of 2.26 and 2.22 Å, respectively,

and the corresponding angles of 149 and 119°. Apparꢀ

ently, it is the presence of the hydrogen bond that is

responsible for the change in the geometric parameters of

phenylazacrown ether 8 compared to benzoazacrown

ethers (see Table 1).

We succeeded in preparing single crystals of the

complexes of benzoazacrown ethers 4b,d, 5b, 6a,d, and

7b with barium perchlorate and the complex of the formyl

derivative of N,N´ꢀdimethylbenzodiazaꢀ15ꢀcrownꢀ5 ether

9 with NaClO₄. These compounds were studied by Xꢀray

diffraction. Compound 9 ²¹is a close structural analog of

diazacrown ether 7b, which differs from the latter only by

the substituent in the benzene fragment of the molecule.

Hence, the geometric characteristics of crown ether 9 can

be considered as common for the complexes of this type

of ligands with Na⁺ions.

Selected geometric characteristics of the metal comꢀ

plexes are given in Table 2. In the complexes, the lone

pairs of all heteroatoms of the macrocycle are directed to

the metal cation; the M^m+...O—C, M^m+...N—C, and

M

^m+...N—H, angles are in the ranges of 105.6(3)—

125.6(2), 97.0(2)—116.2(2), and 96(2)—100(2)°, respecꢀ

tively, which is, on the whole, favorable for the interacꢀ

tions between the sp²ꢀ or sp³ꢀhybridized O and N atoms

and the metal cations. In the complexes with barium

cations, the M^m+...O_mc* and M^m+...N distances are in the

ranges of 2.710(3)—2.930(2) and 2.897(4)—3.058(3) Å,

respectively. In the complex 9•NaClO₄, the correspondꢀ

ing parameters are 2.329(2)—2.506(2), and 2.548(2),

2.554(3) Å. Taking into account the van der Waals radii of

the O and N atoms (~1.4 and 1.5 Å, respectively), the

distances between the heteroatoms of the macrocycles

and the metal cations are indicative of approximately

the same degree of involvement of all heteroatoms in the

binding of M^m+. The barium cations deviate from

the mean plane passing through all heteroatoms of the

macrocycle by 1.60—1.75 Å, whereas the sodium cation

in the complex with compound 9 deviates from the correꢀ

sponding plane by only 0.86 Å. Undoubtedly, this differꢀ

ence is attributed to the smaller ionic radius of the Na⁺

ion than that of Ba²⁺(0.95 and 1.34 Å, respectively),

which allows the Na⁺cation to move deeper into the

cavity of the 15ꢀmembered macroheterocycle. In comꢀ

pounds 4d and 6d, the CH₂CO₂Et side chain is also

involved in the coordination of the Ba²⁺ions through

the carbonyl oxygen atom. Interestingly, the Ba²⁺...O/N

distances and the deviation of the cation from the

mean plane of the macrocyclic system in the complexes

4d•Ba(ClO₄)₂and 6d•Ba(ClO₄)₂are slightly larger than

The structures of the complexes are shown in Figs 3

and 4. The asymmetric units of 5b•Ba(ClO₄)₂•0.5H₂O,

6a•Ba(ClO₄)₂, and 6d•Ba(ClO₄)₂contain two indepenꢀ

dent complexes. In one of the independent complexes

6a•Ba(ClO₄)₂, the fragment of the polyether chain

* Hereinafter, the atoms of the macrocyclic moiety are denoted

by the subscript mc.

986

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

those in the other complexes (see Table 2). This indicates

that the ligand core is somewhat strained due to the

involvement of the carbonyl oxygen atom in the coordiꢀ

nation sphere of the metal cation. The shortest Ba²⁺...O

distance (O is the neutral atom) (2.683(4) Å) is observed

in the structure of 5b•Ba(ClO₄)₂•0.5H₂O for the coordiꢀ

nated water molecule H₂O(1W). A comparison of this

distance with the Ba²⁺...O_mcdistances shows that the arꢀ

rangement of the oxygen atoms of the macrocyclic system

in all the complexes under study is not optimum for the

strongest ionꢀdipole interactions as a result of the limited

possibility for the matching of the conformation of the

O(12)

O(13)

C(17)

O(14)

Cl(1)

O(24)

O(12)

O(11A)

O(22)

O(11)

O(13)

Cl(1)

O(21A)

C(18)

O(6)

C(16)

O(22)

O(23)

Cl(2)

O(14A)

Cl(2A)

O(24)

C(15)

Cl(1A)

O(24A)

O(14)

O(22A)

O(21)

O(5)

O(23)

O(11)

C(15)

Cl(2)

O(21)

Bа(1)

O(12A)

O(13A)

Ba(1)

C(12)

O(23A)

C(12)

C(11)

C(14)

C(11)

N(1)

C(1)

N(1)

C(3)

C(13)

C(1)

C(14)

C(5)

C(2)

C(1)

O(3)

C(10)

C(9)

O(4)

C(13)

C(10)

O(4)

O(2)

C(4)

C(3)

C(4)

C(6)

O(1)

C(7)

O(2)

O(1)

C(7)

C(5)

C(9)

C(6)

C(8)

4d•Ba(ClO₄)₂

4b•Ba(ClO₄)₂

C(9´)

C(8´)

C(10´)

C(11´)

C(12)

C(10)

C(7´)

N(3)

O(44)

O(4)

O(5)

Ba(2)

C(11)

C(15)

C(8)

C(9)

O(2)

C(12´)

C(13´)

C(15´)

C(7)

C(6)

N(1)

O(3)

O(22)

O(5)

O(6)

O(43)

C(13)

O(1)

C(5)

C(4)

C(3)

C(16)

O(6)

Cl(4)

O(41)

C(1´)

C(14´)

N(4)

O(13)

O(4)

C(4´)

C(1)

O(42)

C(6´)

C(3´)

O(21)

O(12)

Cl(1)

C(18)

C(2)

C(2´)

Ba(1)

Cl(2)

O(33)

Cl(3)

O(23)

C(14)

O(1W) O(23)

O(14)

O(24)

C(16´)

C(17)

O(34)

Cl(1)

O(13)

O(43)

O(11)

C(18´)

O(14)

O(21)

O(24)

O(31)

C(17´)

O(44)

O(12)

O(22)

Cl(2)

O(32)

Cl(4)

C(4´)

Ba(2)

C(6´)

O(34)

O(11)

C(16)

C(15)

C(5´)

C(1´)

O(5´)

O(6´)

C(16´)

O(1´)

C(7´)

C(8´)

C(3´)

C(2´)

O(41)

O(32)

O(42)

O(4´)

Cl(3)

O(31)

Ba(1)

O(33)

C(11)

C(15´)

C(10´)

N(2)

C(11´)

C(9´)

O(3´)

C(2)

C(1)

N(2)

C(14´)

C(13´)

O(2´)

C(3)

C(14)

C(13)

O(1)

C(12´)

O(2)

C(6)

O(3)

C(12)

C(4)

N(1)

C(5)

C(7)

C(10)

6d•Ba(ClO₄)₂

C(9)

C(8)

5b•Ba(ClO₄)₂•0.5H₂O

Fig. 3. Molecular structures of the complexes 4b•Ba(ClO₄)₂, 4d•Ba(ClO₄)₂, 5b•Ba(ClO₄)₂•0.5H₂O (two independent complexes),

and 6d•Ba(ClO₄)₂(two independent complexes). Most of the hydrogen atoms in the complexes 5b•Ba(ClO₄)₂•0.5H₂O and

6d•Ba(ClO₄)₂are omitted for simplicity. Here and in Fig. 4, the atoms of the perchlorate anions labeled with A are related to the

unlabeled atoms by the symmetry operation; thermal ellipsoids are drawn at the 50% probability level; the coordination bonds are

indicated by dashed lines.

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

987

15ꢀmembered macrocyclic ligands to the coordination

requirements of the barium cation.

5b•Ba(ClO₄)₂•0.5H₂O (see Table 2), in which two

nitrogen atoms bound to the benzene ring in both indeꢀ

pendent ligand molecules are sp³ꢀhybridized due to the

involvement of their lone pairs in the coordination

of Ba²⁺ions, and apparently the degree of conjugation of

these nitrogen atoms to the benzene ring is low (see

below). In the structures of the complexes of monoꢀ

azacrown ethers 6a and 6d, the conformation of one of

the C_Ar—C_Ar—O—C fragments is indicative of a substanꢀ

tial disturbance of the conjugation of the O atom to the

benzene ring (the corresponding torsion angles are in

the range of –62.7—56.1°), whereas the conformation

of the second C_Ar—C_Ar—O—C fragment in these strucꢀ

tures corresponds to the retention of efficient conjugation

(the torsion angles are in the range of –20.2—19.6°).

The insufficiently high accuracy of the Xꢀray diffracꢀ

tion data for all the complexes under study did not allow

us to reliably compare the bond length distribution in the

benzene fragments of the complexes and the free ligands,

although there is a tendency to equalize these bond lengths

in the first case. The aboveꢀmentioned main characterisꢀ

tic features of benzocrown ethers, such as the systematic

deviation of the bond angles at the C(1) and C(6) atoms

exocyclic with respect to the benzene ring from the ideal

value of 120° and the pronounced sp²hybridization of the

O atoms conjugated to the benzene ring, are observed also

in the complexes of benzoazacrown ethers with sodium

and barium cations. The exception is the structure of

O(33)

O(13)

O(44A)

O(34)

O(42A)

O(31)

Cl(3)

O(24A)

Cl(1)

O(21A)

O(12)

O(14)

O(32)

O(41A)

O(43)

Cl(4A)

O(42)

Cl(4)

O(22A)

O(11)

O(22)

O(23)

Cl(2)

Cl(2A)

O(41)

Ba(2)

O(43A)

C(11)

O(23A)

C(14A)

O(21)

C(13)

O(44)

C(14´)

H(2)

O(24)

N(2)

Ba(1)

H(1)

N(1)

C(10)

C(11´)

C(1´)

O(7)

C(2´)

O(4)

C(1)

O(8)

O(3)

C(13A)

C(10´)

C(12´)

C(13´)

C(2)

C(12)

C(14)

C(3´)

C(4´)

O(6)

O(5)

O(1)

C(9´)

O(2)

C(3)

C(9)

C(6´)

C(6)

C(8´)

C(5´)

C(7)

C(7´)

C(5)

C(8)

C(4)

6a•Ba(ClO₄)₂

O(14)

O(13)

O(12)

O(14)

Cl(1)

O(11A)

Cl(1)

O(24)

O(13)

O(11)

O(12A)

C(15)

Cl(1A)

O(11)

Cl(2)

O(23)

O(21)

O(12)

C(5)

C(4)

Ba(1)

O(13A)

O(14A)

N(1)

C(8)

C(7)

C(6)

O(22)

C(17)

C(3)

C(9)

C(7)

C(5)

C(4)

C(6)

N(1)

C(2)

C(1)

C(9)

O(1)

Na(1)

C(16)

N(2)

O(2)

C(8)

O(1)

O(2)

C(10)

O(4)

C(10)

C(11)

O(3)

C(16)

C(3)

O(3)

C(1)

C(2)

C(12)

C(14)

C(11)

C(14)

C(13)

N(2)

C(12)

C(13)

9•NaClO₄

7b•Ba(ClO₄)₂

Fig. 4. Molecular structures of the complexes 6a•Ba(ClO₄)₂(two independent complexes), 7b•Ba(ClO₄)₂, and 9•NaClO₄. Most of

the hydrogen atoms in the complexes 6a•Ba(ClO₄)₂are omitted for simplicity.

988

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

989

Apparently, this feature is associated with the fact that the

N atom is far distant from the benzene ring in ethers 6a

and 6d, resulting in the necessity of a more substantial

conformational rearrangement of the macrocycle for the

involvement of all its heteroatoms in the coordination to

the barium cation.

O(6)

O(5)

Ba(1)

Ba(1A)

The conformational changes of the macrocycle in

compound 6a upon the formation of the complex with

Ba(ClO₄)₂is shown in Fig. 5. It can be seen that the

largest conformational rearrangement is observed in

the region of the nitrogen atoms due to the necessity

of the reorientation of the nitrogen lone pairs toward

the barium cation that is located above the center of the

macrocyclic cavity. It should be emphasized that the

hydrogen atoms of the NH groups, which are directed to

the center of the macrocyclic cavity and form hydrogen

bonds with the oxygen atoms in the free ligand, are

directed away from the center of the macrocyclic cavity

in the complex 6a•Ba(ClO₄)₂. Therefore, the formation

of metal complexes leads to the cleavage of the intramoꢀ

lecular NH...heteroatom hydrogen bonds, which should

decrease the stability of these complexes compared to the

complexes with the related ligands containing tertiary

nitrogen atoms (see below).

In all the complexes under study, the nitrogen atoms

of crown ethers have a pronounced pyramidal configuraꢀ

tion close to the ideal sp³ꢀhybridized state. The sums of

the bond angles at the N atoms vary in the range of

327.9(2)—336.3(3)° (see Table 2). A comparison of the

sums of the bond angles at the N atoms in the structures

of 4b•Ba(ClO₄)₂and 4d•Ba(ClO₄)₂, in which the nitroꢀ

gen atom is bound to the benzene ring, with the correꢀ

sponding parameters of the related Nꢀmethylbenzoazaꢀ

15ꢀcrownꢀ5 ethers 1b and 1e (351.4(1) and 349.4(3)°,

N(1)

O(3)

O(4)

O(6C)

N(2C)

O(2)

O(1)

O(5B)

O(5C)

Fig. 6. Superposition of the structures of compounds 1b,e and

the complexes 4b•Ba(ClO₄)₂and 4d•Ba(ClO₄)₂based on the

benzene rings. The perchlorate anions and the hydrogen atoms

are omitted. The coordination bonds are indicated by dashed

lines.

respectively)^13,26and a comparison of the N—C_Arbond

lengths in the complexes of compounds 4b,d (1.445(5)

and 1.443(4) Å) and free crown ethers 1b,e (1.389(2) and

1.386(5) Å) clearly show that the nitrogen atoms are more

sp³ꢀhybridized and their conjugation to the benzene ring

in the metal complexes is weaker. The differences in the

conformations of the macroheterocycles in all four comꢀ

pounds are insignificant (Fig. 6), which indicates that the

Nꢀalkyl derivatives of benzomonoazaꢀ15ꢀcrownꢀ5 ethers

containing the nitrogen atom conjugated to the benzene

ring are largely preorganized for the formation of comꢀ

plexes with metal cations.

¹H NMR spectroscopic studies. One of the characterꢀ

istic features of the spectral behavior of free benzoꢀ

azacrown ethers is that the rotation of the acetyl group

around the N—COMe bond in amide 6c is slow on the

¹H NMR time scale (500 MHz) with the result that all

eight CH₂groups of the formally symmetric macrocycle

appear to be nonequivalent due to the anisotropic effect

of the C=O group. The ¹H NMR spectrum of diamide 7c

is more complex in the region of signals of methylene

groups of the macrocycle due to the slow rotation of

two Nꢀacetyl fragments and shows also three signals

of methyl groups at δ 2.0 with an integral intensity ratio of

1 : 1.9 : 1.7. Three C=O stretching vibrations are observed

at 1620—1640 cm^–1in the IR spectrum of solid diamide

7c (see the Experimental section). Apparently, all the

aboveꢀmentioned signals correspond to three theoretiꢀ

cally possible conformers of 7c containing NCOMe

fragments in different orientations with respect to the

O(3A)

C(14)

O(3)

O(7A)

O(4)

C(1)

O(7)

N(1A)

N(1)

H(1)

C(2)

O(8)

Ba(1)

Ba(2)

C(3)

C(4)

H(2)

N(2)

H(1A)

H(2A)

N(2A)

O(5)

C(6)

O(1)

O(2)

O(2A)

O(6)

C(5)

C(7)

O(6A)

Fig. 5. Superposition of the structures of benzoazaꢀ15ꢀcrownꢀ5

ether 6a (two independent molecules) and 6a•Ba(ClO₄)₂(two

independent complexes) based on the benzene rings. The perꢀ

chlorate anions and the hydrogen atoms are omitted (except for

the H atoms of the NH groups). The coordination bonds are

indicated by dashed lines.

1

benzene ring. The H NMR spectra of amides 4c and 5c

are complex and consist of strongly overlapping signals

with high multiplicity for 16 nonequivalent protons of the

990

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

Δδ_H

methylene groups of the macrocycle. This fact indicates

that these compounds exist in solution predominantly in

one conformation, which is most likely identical to those

found in the crystals of these compounds, as confirmed by

the correlations between the upfield shifts (by ~0.35 ppm)

of the signals of the methyl groups of amides 4c and 5c

compared to the corresponding signals of amides 6c

and 7c and by the presence of the methyl groups in the

shielding region of the benzene rings in crystalline amides

4c and 5c (see Fig. 1). Apparently, the presence of acetyl

groups at the nitrogen atoms in benzoazaꢀ15ꢀcrownꢀ5

ethers containing N atoms bound to the benzene rings

leads to the steric strain in the macrocyclic moieties, which

substantially restricts their conformational transforꢀ

mations.

0.5

0.4

H(15),

H(16)

H(14),

H(17)

0.3

0.2

CH₂O

0.1

0

CH₂CH₂N

–0.1

–0.2

–0.3

MeN

CH₂N

0.5

1.0

1.5

2.0

2.5 С_Na/С_5b

The ¹H NMR spectroscopic studies of benzoazacrown

ethers 4—7 and model compounds 2a,b and 3a in MeCNꢀd₃

showed that the signals for most of protons of these ligands

are strongly shifted downfield (Δδ_H) upon the addition of

an excess of metal (Na, Ca, Ba, Ag^I, or Pb^II) or ethylꢀ

ammonium perchlorates. This behavior is characteristic

of inclusion complexes in which the M^m+ion is bound to

all heteroatoms of the macrocycle (Scheme 3) due to the

hydrogen bonding and/or ionꢀdipole interactions, resultꢀ

ing in the shift of the electron density from all atoms of

the ligand toward the cation (the electronꢀwithdrawing

effect of the cation). The common tendency is that the

Δδ_Hvalues are larger in the case of doubly charged cations

than those for monovalent cations. In the case of the

doubly charged cations under study, the largest downfield

shifts (Δδ_Hup to 0.75 ppm) were observed for the comꢀ

plexes with Ca²⁺and Pb²⁺ions evidently due to the high

charge density on these metal cations and the high affinity

of lead(^II) cations for N and O atoms. Silver(I) cations,

unlike the other metal cations under study, form comꢀ

plexes with ligands 3—7, in which the largest Δδ_Hvalues

are observed for the signals of the groups bound to the

nitrogen atoms. Undoubtedly, this is evidence that the N

atoms make a larger contribution to the binding of the

silver cation than the O atoms due to the high affinity of

the soft Ag⁺ion for the soft nitrogen atoms compared to

the hard oxygen atoms.²⁷

Fig. 7. Plots of the changes in Δδ (Δδ = δ (5b—NaClO₄) –

δ (5b)) vs. the ratio of the concentr^Hations of NaClO₄and

5^Hb (C_Na/C_5b) for the signals of all protons of compound 5b in

MeCNꢀd₃.

H

The exceptions are the signal for protons of the CH₂N

and MeN groups of azacrown ethers 3—5 containing

nitrogen atoms bound to the benzene ring, which show

upfield shifts to –0.24 ppm upon the addition of some

salts. The largest upfield shifts are observed in the presꢀ

ence of Na⁺ions, which have the lowest charge density

among the metal cations under study (except for Ag⁺)

and, at the same time, form relatively stable complexes

with azacrown ethers (see below). Figure 7 exemplifies

the changes in the Δδ_Hvalues for the signals for protons of

benzodiazacrown ether 5b depending on the ratio of the

concentrations of NaClO₄and 5b (C_Na/C_5b). Unlike the

monotonic downfield shift of the signals for most of proꢀ

tons with increasing ratio C_Na/C_5b, the signals of the CH₂N

and MeN groups are gradually shifted to higher fields.

It should be noted that the shape of the dependences

Δδ_H—(C_Na/C_5b) is indicative of the relatively low stability

constant of the complex 5b•Na⁺(K₁< 10⁵L mol^–1),

because Δδ_Hdo not reach the maximum values even in

the presence of a threefold excess of Na⁺ions.

This abnormal behavior of the signals of the methyl

and methylene groups bound to the nitrogen atom is

apparently attributed to a change in the geometry of the

N atom and the conformational rearrangement of macroꢀ

cycles 3—5 upon the binding of cations. The reorientaꢀ

tion of the lone pairs of all heteroatoms toward the center

of the macrocyclic cavity occupied by a metal or ethylꢀ

ammonium cation leads to a substantial weakening of the

conjugation of the nitrogen lone pairs to the benzene

ring, the deviations of the substituents at the N atoms

from the plane of the benzene ring being evidently larger

than those in the free ligands (see above). Larger deviaꢀ

tions of the N substituents lead to their shift from the

deshielding region of the benzene ring to the shielding

Scheme 3

X, Y, Z, Q = O, NR; M^m+is the metal or ethylammonium ion

(m = 1, 2)

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

991

region, resulting in the upfield shifts of the signals for the

protons of the aboveꢀmentioned substituents.

disturbance of the conjugation of its nitrogen atoms to the

benzene ring, as evidenced by larger downfield shifts of

the signals for protons of the benzene ring in the comꢀ

plexes compared to the free ligands (see, for example,

Fig. 7) and the virtually sp³ꢀhybridized state of the N atoms

in the complex with barium perchlorate (see Table 2).

The deviations of the Nꢀmethyl and Nꢀmethylene groups

from the plane of the benzene ring in the complexes of 5b

are apparently still larger than those in the complexes

with monoazacrown ethers 4b,d. This is confirmed by

the Xꢀray diffraction data for the crystalline complex

5b•Ba(ClO₄)₂•0.5H₂O (see Fig. 3), in which the

C_Ar—C_Ar—N—CH₂and C_Ar—C_Ar—N—Me torsion

angles are in the ranges of –87.3—76.0° and –47.4—40.1°,

respectively.

Smaller upfield shifts are observed also for the signals

of the CH₂N groups upon the formation of complexes of

Na⁺, Ba²⁺, and EtNH₃ions with benzoazacrown ethers

+

6 and 7 (Δδ_Hup to –0.04 and –0.16 ppm, respectively).

Undoubtedly, in this case a decrease in Δδ_Hcompared

to the analogous effects in the complexes of compounds

3—5 is associated with the smaller influence of the conꢀ

formational changes of the macrocycles in compounds 6

and 7, in which the nitrogen atoms are distant from the

benzene ring. Therefore, the positions of the signals for

protons of azacrown ethers in the NMR spectra are deterꢀ

mined by two opposite effects, such as the electronꢀwithꢀ

drawing effect of the cation and the change in the position

of the crown ether moieties with respect to the benzene

ring upon the complex formation.

In addition, one of characteristic features of the comꢀ

plex formation of the azacrown ethers under study is that

the complexes of compounds 4b,d, 5a,b, 6a,b,d, 7a,d, and 8

with Ca²⁺and Ba²⁺ions have a high kinetic stability,

resulting in a substantial broadening of the signals for

protons of the macroheterocycle (up to the nonequivaꢀ

lence of the analogous methylene groups in the formally

symmetric structures) or even in the nonequivalence of

the geminal protons of the methylene groups as a result

The fact that the complex formation causes changes in

the positions of the CH₂N and MeN groups with respect

to the plane of the benzene ring in compounds, in which

the nitrogen atom is bound to the benzene ring, was

confirmed by comparing the Xꢀray diffraction and NOESY

data for compounds 4b,d and their complexes with the

earlier results^13,26for the structurally related Nꢀmethylꢀ

benzomonoazaꢀ15ꢀcrownꢀ5 ethers 1b,e. The NOESY

spectra of free compounds 4b,d show much more intense

crossꢀpeaks between the NCH₂(substituent) (or NMe)

group and the ortho proton of the benzene ring compared

to the crossꢀpeaks from the analogous interaction involvꢀ

ing the NCH_2,mcgroup, which is indicative of the close

proximity of the first two fragments and is in good agreeꢀ

ment with the Xꢀray diffraction and NOESY data for

compounds 1b,e, in which the shortest NMe...HC_oand

NCH₂...HC_odistances are 2.20 (in both structures) and

4.09, 4.19 Å, respectively. The nitrogen lone pairs in azaꢀ

crown ethers 1b,e are efficiently conjugated to the benzene

ring, and the sums of the bond angles at these atoms are

351.4(1) and 349.4(3)°, which indicates that the N atoms

are in the state intermediate between the sp²and sp³

hybridization. Therefore, the geometry of the nitrogen

atoms and the conformations of the macrocyclic moieties

in free compounds 4b,d and 1b,e are apparently very simiꢀ

lar. In the complexes 4b,d•M^m+, the nitrogen atoms are

almost fully sp³ꢀhybridized (see Table 2) and the deviaꢀ

tions of the Nꢀsubstituents from the dishielding plane of

the benzene ring are larger than the corresponding charꢀ

acteristics of the free ligands. This is clearly seen upon

the superposition of the structures of compounds 1b,e

and the complexes of 4b,d with Ba(ClO₄)₂(see Fig. 6).

Thus, the C_Ar—C_Ar—N—C_mcand C_Ar—C_Ar—N—C(substiꢀ

tuent) torsion angles in 1b,e are –139.0, –140.6° and 6.5,

1.2° respectively, whereas the corresponding angles in

4b,d•Ba(ClO₄)₂are –104.5, –106.8 and 19.9, 19.9°.

The formation of the complexes of N,N´ꢀdimethylꢀ

benzodiazacrown ether 5b apparently also leads to the

1

of the conformational exchange slow on the H NMR

time scale. In addition to the aboveꢀmentioned effects,

most of the complexes with Pb²⁺ions are characterized

also by the slow ligand exchange between the free state

and different types of the complexes, which is determined

by the exceptionally high affinity of these cations for

N,Oꢀcontaining macrocyclic ligands. These effects often

attend the high thermodynamic stability of the complexes.

In most cases, this fact was confirmed by the quantitative

study of the stability of the complexes of the aboveꢀmenꢀ

tioned compounds with Ca²⁺, Ba²⁺, and Pb²⁺ions. In the

case of compound 7b, the aboveꢀmentioned broadening

and the nonequivalence of the signals for protons were

observed in the presence of all the cations under study.

This is indirectly indicative of the high affinity of the

ligands having this structure for cations of different nature

(and, as a consequence, of the low selectivity of these

ligands). On the contrary, the formation of the complexes

of amide azacrown ethers 6c and 7c with Ca²⁺ions leads

to an increase in the rate of conformational exchange

compared to the free ligands (see above), resulting in the

coalescence of the signals for the equivalent protons.

The quantitative determination of the stability of the

complexes of benzoazacrown ethers 4—7 and model crown

ethers 2a,b, 3a, and 8 with metal perchlorates (Na, Ca,

Ba, Ag^I, and Pb^II) and EtNH₃ClO₄in MeCNꢀd₃was carꢀ

ried out by the ¹H NMR titration. In most cases, the

changes in the chemical shifts of protons of the ligands

(L) depending on the ratio of the concentrations of M^m+

and L are well described by the model with account for

the equilibrium

992

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

Table 4. Stability constants (K) of the complexes of crown ethers

a

L + M^m+

L•M^m+

,

(1)

4c,d, 5a,c, 6c,d, 7a,c,d, and 8 with Ca(ClO₄)₂

where K₁/L mol^–1is the stability constant of the complex

of the composition 1 (L) : 1 (M^m+). In some cases, good

results were obtained when the equilibriums (1) and (2)

were taken into account

Ligand

logK₁(logK₂)^b

Ligand

logK₁(logK₂)^b

4c

4d

2.8 (2.3)

8.0^c

6d

7a

8.1^c

7.9^c

5a

4.2

7c

2.9 (3.7)

8.6^c

3.3 (3.5)

L•M^m++ L

(L)₂•M^m+

,

(2)

5c

6c

2.4 (2.2)

2.5 (2.3)

7d

8

where K₂/L mol^–1is the stability constant of the sandwich

complex of the composition 2 (L) : 1 (M^m+). In the

cases higher than the upper limit of applicability of the

direct titration (K₁≥ 10⁵L mol^–1), we used the competiꢀ

^aThe ¹H NMR titration in MeCNꢀd₃, 30 °C.

^bK₁/L mol^–1= [L•Ca²⁺]/([L]•[Ca²⁺]), K₂/L mol^–1= [(L)₂•Ca²⁺]/

/([L]•[L•Ca²⁺]); the error of the determination of the stability

constants is 20% for the direct titration and 30% for the

competitive titration.

1

tive H NMR titration (see the Experimental section).

^cCompetitive with 2a.

The stability constants (logK₁and logK₂) are given in

Tables 3 and 4.

A comparison of the stability constants of the comꢀ

plexes of benzoazacrown ethers 4a and 6a containing

secondary nitrogen atoms, Nꢀmethyl derivatives 4b—7b,

and model compounds 2a,b and 3a with all metal and

ethylammonium cations showed that the stability of

the complexes of most of the compounds increases in the

series EtNH₃⁺< Na⁺≤ Ba²⁺< Ca²⁺< Pb²⁺(see Table 3).

This order of changes in the stability constants correlates

with the downfield shifts Δδ_Hupon the complex formaꢀ

tion and is attributed to the high affinity of Pb²⁺ions for

Oꢀ and O,Nꢀmacrocyclic ligands and a strengthening of

ionꢀdipole interactions in host—guest complexes due to

an increase in the surface charge density in the aboveꢀ

given sequence of the cations (except for Pb²⁺), as well as

to the better correspondence between the cavity size of

the 15ꢀmembered macrocycles and the diameters of the

Na⁺and Ca²⁺ions.

Exceptions from this rule are the complexes with Ag⁺

ions, whose position in the series of stability of the comꢀ

plexes with crown ethers depends on the number of nitroꢀ

gen atoms and their position in the macrocycle. Benzoꢀ

crown ethers 2a and 4a are virtually incapable to bind Ag⁺

ions, whereas the stability of the complexes of diazacrown

ethers 5b and 7b with Ag⁺is comparable to that of the

related complexes with Na⁺and Ba²⁺ions. Undoubtedly,

this complexing ability is determined by the high affinity

of the soft Ag⁺ion for sp³ꢀhybridized nitrogen atoms

and, on the contrary, by the low affinity for hard oxygen

atoms.²⁷

Table 3. Stability constants (K) of the complexes of crown ethers

2a,b, 3a, 4a,b, 5b, 6a,b, and 7b with metal and ethylammonium

perchlorates^a

Ligand

logK₁(logK₂)^b

Ba²⁺Ag⁺

Na⁺Ca²⁺

Pb²⁺EtNH₃

+

d

2a

2b

3a

4a

~5

4.8^c

5.6^c5.4 (5.1)^c<0.5

—

2.4

2.2

1.8

0.9

3.5

2.8

1.4

4.3

4.4

4.6

4.4 (4.2)

4.0

—

>5

6.2 (4.2)^e

0.8

>5

7.3^f

3.1 (2.4) <0.5

>5

7.8 (4.2)^e

4b

5b

5.0^g

3.4

7.3^g

6.2^g

5.4^g

2.3

3.6

7.9^e

3.0

2.0

d

4.40

—

d

6a

6b

3.3

5.7^g

6.5^g

7.1^g

3.80

5.6^g

3.3

4.4

—

2.7

3.9

d

—

d

7b

7.1^g

8.2^g

7.1^g

7.0^h

—

>5

5.6^h

^aThe ¹H NMR titration in MeCNꢀd₃, 30 °C.

b

K₁/L mol^–1

= =

[L•M^m+]/([L]•[M^m+]), K₂/L mol^–1

[(L)₂•M^m+]/([L]•[L•M^m+]); the error of the determination of

the stability constants is 20% for the direct titration and 30%

for the competitive titration.

The regularities of the formation of more stable comꢀ

plexes with the cations under study were found in the

following series of crown ethers: 4a < 3a ≤ 2b ≈ 5b ≤ 6a ≤

2a ≤ 4b ≤ 6b < 7b. Therefore, the stability of the comꢀ

plexes increases as the oxygen atoms in benzoꢀ15ꢀcrownꢀ

5 ether are successively replaced by NMe groups. It should

be noted that benzoazacrown ethers containing nitrogen

atoms distant from the benzene ring form more stable

^cCompetitive with 2b.

^dThe ligand exchange is slow on the ¹H NMR time scale and

hinders the accurate measurement of Δδ values.

H

^eCompetitive with 3a.

^fCompetitive with 2c; the direct titration in the 2c—Pb(ClO₄)₂

system gave logK₁= 4.5, logK₂= 5.0.

^gCompetitive with 2a.

^hCompetitive with 6b.

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

993

complexes than the isomers containing nitrogen atoms

bound to the benzene ring. This fact is associated with the

electronꢀwithdrawing effect of the benzene ring, resulting

in a decrease in the electronꢀdonating ability of heteroꢀ

atoms bound to this ring, as well as with a substantial

contribution of the sp²ꢀhybridized state of these N atoms,

resulting in the involvement of their lone pairs in the

efficient conjugation to the π system of the benzene ring

and, consequently, their switching to the coordination of

cations is hindered. Let us note the exception from this

rule observed for diazacrown ether 5b, consisting in that

the stability of its complexes is low even than that of

monoazacrown ether 4b. Apparently, the methyl groups

in the cis positions at the nitrogen atoms in ether 5b cause

steric hindrance to the location of cations in the macroꢀ

cyclic cavity and can also facilitate the fixation of the

macrocycle in the conformation, which is not optimum

for the complex formation.

The complexes of all benzoazacrown ethers containꢀ

ing secondary nitrogen atoms are less stable than the comꢀ

plexes of their Nꢀmethyl derivatives. This is evidence

for the presence of an intramolecular NH...heteroatom

hydrogen bond in the former compounds (see above),

which hinders the location of cations in the macrocyclic

cavity and the conformational changes of the macrocycle

necessary for the reorientation of the lone pairs of all

heteroatoms toward the cation.

It should be emphasized that, in some cases, it was

impossible to determine the stability constants of the

complexes with Pb²⁺ions due to very high values and

the aboveꢀmentioned exchange slow on the ¹H NMR

time scale between the free ligand and several types of

complexes having, apparently, the composition 1 (L) : 1 (Pb²⁺)

or 2 (L) : 1 (Pb²⁺). Each of these complexes gives a comꢀ

plex set of overlapping signals indicative of the nonequivꢀ

alence of the geminal protons of all methylene groups in

the macrocycle.

It is important that the stability of the complexes of

Nꢀmethylbenzomonoazacrown ether 4b containing the

nitrogen atom bound to the benzene ring with metal and

ethylammonium cations is comparable to or even higher

than the stability of the corresponding complexes of

benzoꢀ15ꢀcrownꢀ5 ether and is substantially higher than

the stability of the complexes of Nꢀphenylazaꢀ15ꢀcrownꢀ5

ether. The selectivity of the complex formation of comꢀ

pound 4b is higher than that of isomeric monoazacrown

ether 6b and diazacrown ether 7b, although the latter two

compounds form more stable complexes. Therefore,

azacrown ethers containing one nitrogen atom bound to

the benzene ring and bearing an Nꢀalkyl substituent are

characterized by the best complexing ability of all the

compounds under study. Hence, macrocyclic ligands of

type 4b are promising for the design of efficient and selecꢀ

tive molecular optical sensors containing the nitrogen

atom conjugated to a chromogen, which will lead to the

shift of absorption and ensure a strong spectral response

to the complex formation.

To compare the stability of the metal complexes of the

other crown ethers, we examined the complex formation

with Ca²⁺ions. These ions form complexes with all the

ligands under consideration, which are easily detectable

by ¹H NMR spectroscopy (see Table 4). The stability

constants of the Ca²⁺complexes with benzoazacrown

ethers of amide type 4c—7c appeared to be the lowest

among all the compounds under study (logK₁= 2.4—2.9).

This is undoubtedly a consequence of the fact that the

acetyl group has a strong electronꢀwithdrawing effect on

the nitrogen atom bound to this group, which hinders the

involvement of the nitrogen lone pair in the coordination

to the cation. Interestingly, sandwich complexes of the

composition 2 (L) : 1 (Ca²⁺), whose stability is compaꢀ

rable to that of the related 1 : 1 complexes, were found in

the systems (4c—7c)—Ca²⁺. Apparently, the formation of

the sandwich complexes is attributed to a decrease in the

cavity size of 15ꢀmembered benzoazacrown ethers due to

the planar geometry of the sp²ꢀhybridized nitrogen atoms,

as was confirmed by the Xꢀray diffraction data for comꢀ

pounds 4c—6c (see Figs 1 and 2 and Table 1). A decrease

in the size of the macrocyclic cavity results apparently in

that the deep penetration of Ca²⁺ions into the cavity of

the azamacrocycle is impossible and, consequently, the

second ligand molecule can be coordinated at the free

side of the cation in the complex of the composition

1 (L) : 1 (Ca²⁺). The formation of the complexes of the

composition 1 : 1 and 2 : 1 with Ca²⁺ions was observed

also for Nꢀphenylazacrown ether 8 with a small cavity size

of the 12ꢀmembered macrocycle.

The opposite effect on the stability of the complexes

was observed in the presence of the Nꢀsubstituents

CH₂CO₂Et in benzoazacrown ethers. Thus, the stability

constants of the complexes of benzoazacrown ethers 4d,

6d, and 7d with Ca²⁺ions increase to logK₁= 8.0—8.6,

and the stability of these complexes is higher than that of

the related complexes of Nꢀmethyl derivatives 4b, 6b, and

7b. As in the case of compounds 4b—7b, the tertiary

nitrogen atoms in 4d, 6d, and 7d are evidently predomiꢀ

nantly sp³ꢀhybridized and are more prone to donating

lone pairs for the formation of coordination bonds

with cations than azacrown ethers 4a—7a containing

secondary N atoms. In addition, the presence of the

oxygen donor atoms in the ethoxycarbonylmethyl group

creates an additional binding region of M^m+. The metal

cations are coordinated through the carbonyl oxygen

atom, as was confirmed by the Xꢀray diffraction data

for the complexes 4d•Ba(ClO₄)₂and 6d•Ba(ClO₄)₂(see

Fig. 3) and the results of IR spectroscopic studies of the

solid metal complexes, which show lowꢀfrequency shifts

of C=O stretching bands in the spectra of the metal comꢀ

plexes down to 21 cm^–1compared to the free ligands (see

the Experimental section). However, it should be noted

994

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

IRꢀ435 and Bruker ISFꢀ113V instruments in Nujol or in films

on KBr. The TLC monitoring was carried out on DCꢀAlufolien

Aluminiumoxid 60 F₂₅₄neutral (Typ E) and Kieselgel 60 F₂₅₄

(Merck) plates. The column chromatography was performed on

Al₂O₃(Aluminium oxide 90 active neutral, 0.063—0.200 mm or

Aluminium oxide 150, basic (type T), 0.063—0.200 mm, Merck)

and SiO₂(Kieselgel 60, 0.063—0.100 mm, Merck). The ¹H NMR

spectra were recorded on a Bruker DRXꢀ500 spectrometer

(500.13 MHz) in DMSOꢀd₆at 25—30 °C using the residual

signals of the solvent as the internal standard (δ 2.50). The

chemical shifts and the spinꢀspin coupling constan^Hts were meaꢀ

sured with an accuracy of 0.01 ppm and 0.1 Hz, respectively. The

assignment of the signals for protons was made based on twoꢀ

that the contribution of the additional coordination of the

cation by carbonyl groups to the stability of the complexes

is relatively low. This may be associated with the coordiꢀ

nation saturation of the Ca²⁺ion even in the complexes of

Nꢀmethyl derivatives 4b, 6b, and 7b or with the steric

strain in the macrocyclic moiety upon the coordination of

the cation by C=O groups (see the above discussion of the

Xꢀray diffraction data).

To conclude, let us note that some metal complexes of

azacrown ethers can be prepared in the solid state by the

crystallization in an appropriate solvent system. Most of

the complexes prepared by this method have the compoꢀ

sition 1 (L) : 1 (M^m+), as was confirmed by elemental

analysis. In most cases, the most complete precipitation

and the formation of highꢀquality crystals stable during

storage were achieved with the use of barium perchlorate.

The aboveꢀmentioned tendency to the formation of

dinuclear systems and the relatively low hygroscopicity

of barium salts can be responsible for the formation of

structured precipitates by the complexes of 15ꢀmembered

azamacrocycles with Ba(ClO₄)₂.

To sum up, we synthesized benzoazaꢀ15ꢀcrownꢀ5

ethers containing different numbers of nitrogen atoms in

different positions in the macrocycle with respect to the

benzene ring and bearing the following N substituents:

H, Me, C(O)Me, or CH₂CO₂Et. The quantitative study

of the complexing ability of the benzoazacrown ethers for

the metal and ethylammonium cations showed that the

most stable complexes are formed by the compounds conꢀ

taining nitrogen atoms with Nꢀalkyl substituents distant

from the benzene ring. However, the selectivity of comꢀ

plex formation appeared to be higher for the crown ether

containing the nitrogen atom bound to the benzene ring

and the Nꢀmethyl substituent. In addition, the stability of

the complexes of this compound is comparable to or even

higher than that of the complexes of benzocrown ether

and is substantially higher than the stability of the corꢀ

responding complexes of phenylazacrown ether with

the same size of the macrocycle. Due to this feature, the

ligands having this structure can be considered as ionoꢀ

phoric blocks for the design of promising selective

molecular optical sensors with a strong spectral respons to

the complex formation.

1

dimensional homonuclear H—¹H COSY and NOESY spectra.

2ꢀAminophenol, oꢀphenylenediamine, and ethyl bromoꢀ

acetate (Aldrich, Merck) were used without additional purificaꢀ

tion. 1,11ꢀDichloroꢀ3,6,9ꢀtrioxaundecane, 1,11ꢀdiiodoꢀ3,6,9ꢀ

trioxaundecane, 1,5ꢀdiaminoꢀ3ꢀoxapentane, N,N´ꢀdimethylꢀ

1,5ꢀdiaminoꢀ3ꢀoxapentane, benzoꢀ15ꢀcrownꢀ5 ether (2a),

4´ꢀformylbenzoꢀ15ꢀcrownꢀ5 ether (2b), Nꢀphenylazaꢀ15ꢀcrownꢀ5

ether (3a), benzoꢀ7ꢀazaꢀ15ꢀcrownꢀ5 ether (6a), and Nꢀmethylꢀ

benzoꢀ7ꢀazaꢀ15ꢀcrownꢀ5 ether (6b) are commercially available

products purchased from the A. V. Bogatsky PhysicoꢀChemical

Institute of the National Academy of Sciences of Ukraine

(Odessa). 1,2ꢀBis(2ꢀiodoethoxy)benzene²⁸and N,N´ꢀdimethylꢀ

(4´ꢀformylbenzo)ꢀ4,10ꢀdiazaꢀ15ꢀcrownꢀ5 ether (9)²¹were synꢀ

thesized according to known procedures. The salts NaClO₄,

Ca(ClO₄)₂, and Ba(ClO₄)₂(Aldrich) were dried in vacuo at 200 °C.

Ethylammonium perchlorate was prepared by the neutralization

of a 70% aqueous ethylamine solution with a 70% aqueous

HClO₄solution (Aldrich) and dried in vacuo at 60 °C. The

salts AgClO₄•H₂O and Pb(ClO₄)₂•3H₂O (Aldrich) were used

without additional purification.

2,3,5,6,8,9,12,13ꢀOctahydroꢀ11Hꢀ1,4,7,10,13ꢀbenzotetraꢀ

oxaazacyclopentadecyne (4a) and 2ꢀ(1,4,7ꢀtrioxaꢀ10ꢀazacycloꢀ

dodecenꢀ10ꢀyl)phenol (8). A. A mixture of 2ꢀaminophenol (8.6 g,

0.079 mol), 1,11ꢀdichloroꢀ3,6,9ꢀtrioxaundecane (18.3 g, 0.079 mol),

and nꢀbutanol (125 mL) was stirred at room temperature under

a nitrogen atmosphere for 6 h and then refluxed for 30 h. After

cooling, a solution of NaOH (6.3 g, 0.16 mol) in water (6 mL)

was added, and the reaction mixture was refluxed with stirring

for 20 h. The precipitate was filtered off, and the filtrate was

concentrated in vacuo and extracted with chloroform (3×20 mL).

The combined extracts were washed with a 5% NaOH solution

and thoroughly concentrated in vacuo. The dry residue was

extracted with hot isooctane (8×30 mL), and the combined

extracts were concentrated in vacuo. The residue was chromꢀ

atographed on SiO₂with elution by a benzene—AcOEt gradient

mixture (0→33%). The product was additionally purified by

chromatography on Al₂O₃(neutral) with elution by a benzene—

AcOEt gradient mixture (0→17%). Product 4a was obtained as a

paleꢀpink powder, m.p. 98—100 °C (cf. lit. data¹⁵: m.p. 100—102 °C),

in a yield of 1.73 g (8%). ¹H NMR, δ: 3.11 (m, 2 H, CH₂N);

3.53—3.60 (m, 8 H, 4 CH₂O); 3.67 (m, 2 H, CH₂CH₂N); 3.72

(m, 2 H, CH₂CH₂OAr); 4.01 (m, 2 H, CH₂OAr); 4.97 (br.s,

1 H, NH); 6.55 (d, 1 H, H(14), J = 7.9 Hz); 6.56 (m, 1 H,

H(16)); 6.79 (m, 1 H, H(15)); 6.80 (d, 1 H, H(17), J = 7.7 Hz).

IR (in Nujol), ν/cm^–1: 3440 (N—H).

Experimental

The melting points (uncorrected) were measured in capilꢀ

laries on a MelꢀTemp II instrument. The mass spectra were

obtained on Varian MAT 311A and Finnigan MAT 8430 instruꢀ

ments using a direct inlet system; the ionization energy was

70 eV. The highꢀresolution mass spectra were measured on a

Finnigan MAT 8430 instrument using perfluorokerosene as the

standard. The elemental analysis was carried out in the Laboraꢀ

tory of Microanalysis of the A. N. Nesmeyanov Institute of

Organoelement Compounds of the Russian Academy of Sciꢀ

ences (Moscow). The IR spectra were recorded on Shimadzu

B. A mixture of 2ꢀaminophenol (2.29 g, 0.021 mol), 1,11ꢀdiiodoꢀ

3,6,9ꢀtrioxaundecane (5.00 mL, 0.023 mol), anhydrous Na₂CO₃

(11.1 g, 0.105 mol), and dry MeCN (250 mL) was refluxed with

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

995

stirring for 30 h. The reaction mixture was filtered off, the

filtrate was concentrated in vacuo, and the residue was chromꢀ

atographed first on SiO₂(a benzene—AcOEt gradient mixture,

0→50%) and then on Al₂O₃(neutral) (a benzene—AcOEt

gradient mixture, 0→17%). Two fractions were collected. The

first fraction was concentrated, and crown ether 4a was obtained

in a yield of 88 mg (1.6%) as a crystalline gray powder,

m.p. 101—102 °C (cf. lit. data¹⁴: m.p. 102 °C). The second

fraction was additionally chromatographed on SiO₂with elution

by a benzene—AcOEt gradient mixture (0→33%). Product 8

was obtained as a pinkish powder, m.p. 73 °C (from a CH₂Cl₂—

hexane mixture; cf. lit. data¹⁴: m.p. 90 °C), in a yield of 155 mg

(2.8%). ¹H NMR, δ: 3.07 (m, 4 H, 2 CH₂N); 3.44 (m, 4 H,

2 CH₂CH₂N); 3.53 and 3.63 (both m, 4 H each, 4 CH₂O); 6.74

(td, 1 H, H(4), J = 7.7 Hz, J = 1.2 Hz); 6.76 (dd, 1 H, H(6),

J = 7.9 Hz, J = 1.2 Hz); 6.93 (td, 1 H, H(5), J = 7.7 Hz, J = 1.3 Hz);

7.16 (dd, 1 H, H(3), J = 7.8 Hz, J = 1.3 Hz); 8.49 (s, 1 H, OH).

IR (in Nujol), ν/cm^–1: 3290 (O—H). MS, m/z (I_rel(%)): 267

[M]⁺(37), 179 (25), 166 (21), 148 (52), 147 (23), 134 (43), 122

(41), 121 (94), 120 (100), 119 (45).

1,2,3,5,6,8,9,11,12,13ꢀDecahydroꢀ4,7,10,1,13ꢀbenzotrioxaꢀ

diazacyclopentadecyne (5a). A mixture of oꢀphenylenediamine

(1.36 g, 0.013 mol), 1,11ꢀdiiodoꢀ3,6,9ꢀtrioxaundecane (3.00 mL,

0.014 mol), anhydrous Na₂CO₃(6.68 g, 0.063 mol), and dry

MeCN (150 mL) was refluxed with stirring for 30 h. The reaction

mixture was filtered off, the filtrate was concentrated in vacuo,

water (100 mL) was added, and the mixture was extracted with

chloroform (4×15 mL). The combined extracts were concenꢀ

trated in vacuo, and the residue was chromatographed first on

Al₂O₃(basic) (a benzene—AcOEt mixture (10 : 1) as the eluent)

and then on SiO₂(a benzene—AcOEt mixture (5 : 1) as the

eluent). The product was purified by the extraction with boiling

hexane (8×20 mL). The combined extracts were concentrated to

~50 mL and then cooled to –10 °C. The precipitate that formed

was filtered off and dried in air. Product 5a was obtained as

colorless crystals, m.p. 108—110 °C (cf. lit. data¹⁴: m.p. 110 °C),

in a yield of 0.84 g (25%). ¹H NMR, δ: 3.12 (m, 4 H, 2 CH₂N);

3.55 and 3.60 (both m, 4 H each, 4 CH₂O); 3.69 (t, 4 H,

2 CH₂CH₂N, J = 5.0 Hz); 4.10 (t, 2 H, 2 NH, J = 5.5 Hz); 6.52

(m, 2 H, H(14), H(17)); 6.61 (m, 2 H, H(15), H(16)). IR (in

Nujol), ν/cm^–1: 3350 (N—H).

H(17)); 6.97 (m, 2 H, H(15), H(16)). IR (in Nujol), ν/cm^–1

:

3331 (N—H). MS, m/z (I_rel(%)): 266 [M]⁺(1), 180 (89), 179 (96),

166 (66), 148 (81), 136 (54), 88 (61), 74 (55), 71 (53), 70 (62),

56 (100).

4,10ꢀDimethylꢀ3,4,5,6,9,10,11,12ꢀoctahydroꢀ2H,8Hꢀ1,7,

13,4,10ꢀbenzotrioxadiazacyclopentadecyne (7b). A solution of

N,N´ꢀdimethylꢀ1,5ꢀdiaminoꢀ3ꢀoxapentane (0.20 mL, 1.4 mmol)

in MeCN (7 mL) was added with vigorous stirring to a mixture

of 1,2ꢀbis(2ꢀiodoethoxy)benzene (0.53 g, 1.3 mmol), anhydrous

K₂CO₃(0.70 g, 5.1 mmol), and dry MeCN (40 mL). The reacꢀ

tion mixture was refluxed for 11 h. The precipitate was filtered

off, the filtrate was concentrated in vacuo, and the residue was

chromatographed on Al₂O₃(basic) with elution by a MeCN—

EtOH gradient mixture (to 20% of the latter solvent). The fracꢀ

tion containing the product was concentrated in vacuo, the resiꢀ

due was extracted with hot hexane (2×40 mL), and the comꢀ

bined extracts were concentrated in vacuo. Product 7b was

obtained as a yellowish viscous oil (cf. lit. data¹⁹: b.p. 170—180 °C

(0.3 Torr)) in a yield of 0.23 g (61%). ¹H NMR, δ: 2.25 (s,

6 H, 2 Me); 2.61 (t, 4 H, 2 CH₂N, J = 5.9 Hz); 2.77 (t, 4 H,

2 CH₂CH₂OAr, J = 4.7 Hz); 3.59 (t, 4 H, 2 CH₂O, J = 5.9 Hz);

3.97 (t, 4 H, 2 CH₂OAr, J = 4.7 Hz); 6.86 (m, 2 H, H(14),

H(17)); 6.93 (m, 2 H, H(15), H(16)). MS, m/z (I_rel(%)): 294 [M]⁺

(2), 211 (14), 194 (36), 193 (100), 185 (28), 180 (15), 136 (11),

102 (15), 88 (44), 72 (11), 58 (30).

13ꢀMethylꢀ2,3,5,6,8,9,12,13ꢀoctahydroꢀ11Hꢀ1,4,7,10,13ꢀ

benzotetraoxaazacyclopentadecyne (4b). Methyl iodide (125 μL,

2.0 mmol) was added to a mixture of azacrown ether 4a (54 mg,

0.2 mmol), NaH (a 60% dispersion in Nujol, 160 mg, 4.0 mmol),

and dry THF (6 mL). The reaction mixture was heated with

stirring at 65 °C until the starting compound 4a was consumed

(40 min, TLC monitoring). Then water (30 mL) was added to

the reaction mixture, the mixture was extracted with chloroform

(3×15 mL), the organic extracts were concentrated in vacuo, and

the residue was chromatographed on Al₂O₃(basic) using benꢀ

zene and then a benzene—AcOEt mixture (2 : 1) as the eluent.

Product 4b was obtained as a yellowish oil in a yield of

54 mg (96%). ¹H NMR, δ: 2.70 (s, 3 H, Me); 3.03 (t, 2 H,

CH₂N, J = 7.5 Hz); 3.54—3.62 (m, 8 H, 4 CH₂O); 3.79 (m, 2 H,

CH₂CH₂OAr); 3.82 (t, 2 H, CH₂CH₂N, J = 7.5 Hz); 4.05 (m,

2 H, CH₂OAr); 6.79—6.89 (m, 4 H, H(14), H(15), H(16), H(17)).

MS, m/z (I_rel(%)): 281 [M]⁺(47), 150 (23), 149 (23), 148 (31),

137 (20), 136 (100), 135 (74), 121 (31), 66 (18), 52 (23).

1,13ꢀDimethylꢀ1,2,3,5,6,8,9,11,12,13ꢀdecahydroꢀ4,7,10,1,13ꢀ

benzotrioxadiazacyclopentadecyne (5b). A mixture of azacrown

ether 5a (57 mg, 0.21 mmol), NaH (a 60% dispersion in Nujol,

170 mg, 4.3 mmol) and dry THF (6 mL) was heated with stirring

at 65 °C for 5 min. Then methyl iodide (133 μL, 2.1 mmol) was

added, and the mixture was heated until the starting compound

5a was consumed (50 min, TLC monitoring). Then water

(30 mL) was added to the reaction mixture, the mixture was

extracted with chloroform (3×25 mL), the organic extracts were

concentrated in vacuo, and the residue was chromatographed

on Al₂O₃(basic) using benzene and then a benzene—AcOEt

mixture (7 : 3) as the eluent. Product 5b was obtained as a

yellowish oil in a yield of 58 mg (92%). ¹H NMR, δ: 2.68 (s, 6 H,

2 Me); 3.23 (t, 4 H, 2 CH₂N, J = 6.3 Hz); 3.48 and 3.53 (both

m, 4 H each, 4 CH₂O); 3.61 (t, 4 H, 2 CH₂CH₂N, J = 6.3 Hz);

6.84—6.91 (m, 4 H, H(14), H(15), H(16), H(17)). MS, m/z

(I_rel(%)): 294 [M]⁺(66), 176 (25), 175 (100), 162 (20), 161 (44),

160 (33), 147 (22), 146 (69), 133 (25), 57 (16).

3,4,5,6,9,10,11,12ꢀOctahydroꢀ2H,8Hꢀ1,7,13,4,10ꢀbenzoꢀ

trioxadiazacyclopentadecyne (7a).

A solution of 1,2ꢀbisꢀ

(2ꢀiodoethoxy)benzene (4.04 g, 9.7 mmol) in a mixture of MeCN

(25 mL) and benzene (6 mL) and a solution of 1,5ꢀdiaminoꢀ

3ꢀoxapentane (1.11 g, 10.6 mmol) in MeCN (25 mL) were

simultaneously added dropwise with vigorous stirring under

reflux to a mixture of anhydrous Na₂CO₃(5.13 g, 0.048 mol)

and dry MeCN (100 mL) for 30 min. Then the mixture was

refluxed for 30 h. The precipitate was filtered off, the filtrate

was concentrated in vacuo, and the residue was chromatographed

on Al₂O₃(neutral) with elution by a benzene—MeCN—propanꢀ

2ꢀol mixture (5 : 4 : 1). The fraction containing the product was

concentrated in vacuo, and the residue was extracted with hot

heptane (3×50 mL). The combined extracts were cooled to

–10 °C, and the precipitate was filtered off and dried in air.

Product 7a was obtained as a white powder, m.p. 92—94 °C

(cf. lit. data¹⁸: m.p. 97—100 °C), in a yield of 0.41 g (16%).

¹H NMR, δ: 2.71 (t, 4 H, 2 CH₂N, J = 4.6 Hz); 2.86 (t, 4 H,

2 CH₂CH₂OAr, J = 4.7 Hz); 3.51 (t, 4 H, 2 CH₂O, J = 4.6 Hz);

4.01 (t, 4 H, 2 CH₂OAr, J = 4.7 Hz); 6.88 (m, 2 H, H(14),

996

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

13ꢀAcetylꢀ2,3,5,6,8,9,12,13ꢀoctahydroꢀ11Hꢀ1,4,7,10,13ꢀ

4,10ꢀDiacetylꢀ3,4,5,6,9,10,11,12ꢀoctahydroꢀ2H,8Hꢀ1,7,

13,4,10ꢀbenzotrioxadiazacyclopentadecyne (7c). A mixture of

diazacrown ether 7a (149 mg, 0.56 mmol) and acetic anhydride

(2 mL) was heated at 100 °C (an oil bath) for 6 h. The reaction

mixture was concentrated in vacuo, and the residue was chromꢀ

atographed on SiO₂using a benzene—MeCN mixture (1 : 1)

and then a benzene—EtOH mixture (5 : 1) as the eluent. Prodꢀ

uct 7c was obtained as a white powder, m.p. 102—104 °C, in a

yield of 167 mg (85%). Found (%): C, 61.80; H, 7.61; N, 7.97.

C₁₈H₂₆N₂O₅. Calculated (%): C, 61.70; H, 7.48; N, 8.00.

¹H NMR, δ: 2.025, 2.034, 2.048 (3 s, 1.3 H, 2.5 H, 2.2 H, 2 Me);

3.53—3.62 (m, 5.4 H, 2.7 CH₂); 3.69 (m, 2.4 H, 1.2 CH₂); 3.73

(m, 2.7 H, 1.35 CH₂); 3.78 (m, 1.5 H, 0.75 CH₂); 4.09 (m, 2.5 H,

1.25 CH₂OAr); 4.15 (m, 1.5 H, 0.75 CH₂OAr); 6.86—6.93 (m,

2 H, H(14), H(17)); 6.93—7.00 (m, 2 H, H(15), H(16)).

IR (in Nujol), ν/cm^–1: 1640, 1633, 1621 (C=O). MS, m/z

(I_rel(%)): 350 [M]⁺(12), 268 (43), 253 (28), 235 (25), 234 (23),

71 (16), 69 (18), 59 (33), 58 (100), 57 (35), 55 (18).

benzotetraoxaazacyclopentadecyne (4c). A mixture of azacrown

ether 4a (160 mg, 0.60 mmol) and acetic anhydride (2 mL) was

heated at 100 °C (an oil bath) for 6 h. The reaction mixture

was concentrated in vacuo. The residue was chromatographed

on SiO₂using AcOEt and then an AcOEt—EtOH mixture

(5 : 1) as the eluent. Product 4c was obtained as a white powder,

m.p. 118—120 °C, in a yield of 176 mg (95%). Found (%):

C, 62.39; H, 7.60; N, 4.30. C₁₆H₂₃NO₅. Calculated (%):

C, 62.12; H, 7.49; N, 4.53. ¹H NMR, δ: 1.63 (s, 3 H, Me);

3.06 (ddd, 1 H, CHH´N, J = 13.1 Hz, J = 9.4 Hz, J = 6.2 Hz);

4.43 (m, 2 H, CH₂O); 3.47—3.57 (m, 6 H, 3 CH₂O); 3.62 (m,

2 H, CH₂CHH´N); 3.71 (m, 2 H, CH₂CHH´OAr); 4.13 (dt,

1 H, CHH´OAr, J = 11.6 Hz, J = 3.1 Hz); 4.18 (ddd, 1 H,

CHH´N, J = 13.1 Hz, J = 9.5 Hz, J = 6.8 Hz); 4.25 (m, 1 H,

CHH´OAr); 6.99 (td, 1 H, H(15), J = 7.7 Hz, J = 0.9 Hz);

7.13 (dd, 1 H, H(17), J = 7.9 Hz, J = 0.9 Hz); 7.25 (dd, 1 H,

H(14), J = 7.7 Hz J = 1.6 Hz); 7.33 (td, 1 H, H(16), J = 7.9 Hz,

J = 1.6 Hz). IR (in Nujol), ν/cm^–1: 1651 (C=O). MS, m/z

(I_rel(%)): 309 [M]⁺(12), 148 (46), 136 (42), 135 (56), 134 (45),

122 (60), 121 (41), 120 (64), 109 (52), 59 (50), 58 (100).

1ꢀAcetylꢀ1,2,3,5,6,8,9,11,12,13ꢀdecahydroꢀ4,7,10,1,13ꢀ

benzotrioxadiazacyclopentadecyne (5c). A mixture of diazacrown

ether 5a (329 mg, 1.24 mmol), acetic anhydride (0.35 mL), and

benzene (20 mL) was heated at 80 °C (an oil bath) for 4 h. Then

MeOH (1 mL) was added. The reaction mixture was kept for 2 h

and concentrated in vacuo. The residue was chromatographed

on SiO₂with elution by a benzene—AcOEt gradient mixꢀ

ture (0→65%). Product 5c was obtained as a white powder,

m.p. 78—79 °C, in a yield of 168 mg (44%). Found (%):

C, 60.67; H, 7.99; N, 8.76. C₁₆H₂₄N₂O₄•0.5H₂O. Calcuꢀ

lated (%): C, 60.55; H, 7.94; N, 8.83. ¹H NMR, δ: 1.67 (s, 3 H,

Me); 2.94 (br.dt, 1 H, CHH´NCO, J = 13.8 Hz, J = 5.1 Hz);

3.17 (dtd, 1 H, CHH´NH, J = 13.2 Hz, J = 6.5 Hz, J = 2.8 Hz);

3.32 (m, 1 H, CHH´NH); 3.39 (ddd, 1 H, CHH´CHH´NCO,

J = 10.3 Hz, J = 8.3 Hz, J = 5.5 Hz); 3.42—3.63 (m, 10 H,

5 CH₂O); 3.68 (m, 1 H, CHH´CHH´NH, J = 10.3 Hz,

J = 6.4 Hz, J = 2.7 Hz); 4.53 (ddd, 1 H, CHH´NCO, J = 13.9 Hz,

J = 8.2 Hz, J = 5.8 Hz); 5.11 (br.t, 1 H, NH, J = 5.4 Hz); 6.64

(td, 1 H, H(16), J = 7.5 Hz, J = 0.9 Hz); 6.74 (dd, 1 H, H(14),

J = 8.1 Hz, J = 0.9 Hz); 7.04 (dd, 1 H, H(17), J = 7.7 Hz, J = 1.4 Hz);

7.17 (td, 1 H, H(15), J = 7.7 Hz, J = 1.4 Hz). IR (in Nujol),

ν/cm^–1: 3380 (N—H), 1657 (C=O). MS, m/z (I_rel(%)): 308 [M]⁺

(38), 293 (64), 291 (89), 163 (89), 147 (89), 145 (45), 133 (69),

132 (39), 121 (44), 119 (100).

Ethyl 2,3,5,6,8,9,11,12ꢀoctahydroꢀ13Hꢀ1,4,7,10,13ꢀbenzoꢀ

tetraoxaazacyclopentadecynꢀ13ꢀylacetate (4d). A mixture of

benzoazacrown ether 4a (107 mg, 0.40 mmol), ethyl bromoꢀ

acetate (49 μL, 0.44 mmol), anhydrous Na₂CO₃(51 mg,

0.46 mmol), and dry MeCN (4 mL) was refluxed with stirring

for 60 h. Then MeCN (20 mL) was added, the precipitate was

filtered off, the filtrate was concentrated in vacuo, and the resiꢀ

due was chromatographed on Al₂O₃(basic) with elution by a

benzene—EtOAc mixture (2 : 1). Product 4d was obtained as

1

a paleꢀyellow oil in a yield of 130 mg (93%). H NMR, δ: 1.17

(t, 3 H, Me, J = 7.1 Hz); 3.34 (t, 2 H, CH₂CH₂N, J = 6.3 Hz);

3.52, 3.56, 3.58, and 3.62 (all m, 2 H each, CH₂O); 3.72 (t, 2 H,

CH₂CH₂N, J = 6.3 Hz); 3.79 (m, 2 H, CH₂CH₂OAr); 4.05 (s,

2 H, CH₂CO₂); 4.06 (m, 2 H, CH₂OAr); 4.07 (q, 2 H, CH₂Me,

J = 7.1 Hz); 6.80 (br.d, 1 H, H(14), J = 4.7 Hz); 6.80—6.85

(m, 2 H, H(15), H(16)); 6.88 (br.d, 1 H, H(17), J = 7.4 Hz).

IR (in film), ν/cm^–1: 1740 (C=O). MS, m/z (I_rel(%)): 353 [M]⁺

(1), 280 (46), 149 (26), 148 (60), 134 (73), 122 (35), 120 (59),

71 (29), 59 (34), 58 (100), 57 (43). Highꢀresolution MS,

Found: m/z 353.1834 [M]⁺. C₁₈H₂₇NO₆. Calculated: M = 353.1838.

Ethyl 2,3,5,6,8,9,11,12ꢀoctahydroꢀ7Hꢀ1,4,10,13,7ꢀbenzoꢀ

tetraoxaazacyclopentadecynꢀ7ꢀylacetate (6d). A mixture of

benzoazacrown ether 6a (201 mg, 0.75 mmol), ethyl bromoꢀ

acetate (100 μL, 0.90 mmol), anhydrous K₂CO₃(416 mg,

0.46 mmol), and dry MeCN (10 mL) was refluxed with stirring

for 20 h. Then benzene (30 mL) was added, the precipitate was

filtered off, the filtrate was concentrated in vacuo, and the

residue was chromatographed on Al₂O₃(neutral) with elution

by a benzene—MeCN mixture (5 : 1). Product 6d was obtained

as a colorless substance, m.p. 50—52 °C, in a yield of 203 mg

(76%). Found (%): C, 61.38; H, 7.67; N, 3.87. C₁₈H₂₇NO₆.

Calculated (%): C, 61.17; H, 7.70; N, 3.96. ¹H NMR, δ: 1.17

(t, 3 H, Me, J = 7.2 Hz); 2.78 (t, 4 H, (CH₂CH₂)₂N, J = 6.0 Hz);

3.41 (s, 2 H, CH₂CO₂); 3.61 (t, 4 H, (CH₂CH₂)₂N, J = 6.0 Hz);

3.72 (m, 4 H, 2 CH₂CH₂OAr); 4.02 (m, 4 H, CH₂OAr); 4.05

(q, 2 H, CH₂Me, J = 7.2 Hz); 6.86 (m, 2 H, H(14), H(17));

6.93 (m, 2 H, H(15), H(16)). IR (in film), ν/cm^–1: 1735 (C=O).

MS, m/z (I_rel(%)): 353 [M]⁺(14), 280 (68), 109 (20), 85 (21),

84 (23), 69 (25), 59 (42), 58 (100), 57 (33), 56 (46), 55 (31).

4,10ꢀBis(ethoxycarbonylmethyl)ꢀ2,3,5,6,8,9,11,12ꢀoctaꢀ

hydroꢀ4H,10Hꢀ1,7,13,4,10ꢀbenzotrioxadiazacyclopentadecyne

(7d). A solution of benzodiazacrown ether 7a (0.60 g, 2.3 mmol),

ethyl bromoacetate (0.55 mL, 5.0 mmol), and dry Et₃N

7ꢀAcetylꢀ2,3,6,7,8,9,11,12ꢀoctahydroꢀ5Hꢀ1,4,10,13,7ꢀbenzoꢀ

tetraoxaazacyclopentadecyne (6c). A mixture of azacrown

ether 6a (205 mg, 0.77 mmol) and acetic anhydride (2 mL) was

heated at 100 °C (an oil bath) for 6 h. The reaction mixture

was thoroughly concentrated in vacuo at 90 °C. Product 6c was

obtained as a white powder, m.p. 85—87 °C, in a yield of 240 mg

(100%). Found (%): C, 62.36; H, 7.70; N, 4.33. C₁₆H₂₃NO₅.

Calculated (%): C, 62.12; H, 7.49; N, 4.53. ¹H NMR, δ: 2.00

(s, 3 H, Me); 3.42 (t, 2 H, CH₂N, J = 5.9 Hz); 3.50 (t, 2 H,

CH₂N, J = 6.6 Hz); 3.62 (t, 2 H, CH₂CH₂N, J = 5.9 Hz); 3.71

(m, 2 H, CH₂CH₂OAr); 3.77 (t, 2 H, CH₂CH₂N, J = 6.6 Hz);

3.78 (m, 2 H, CH₂CH₂OAr); 4.03 (m, 4 H, 2 CH₂OAr); 6.87

(m, 2 H, H(14), H(17)); 6.94 (m, 2 H, H(15), H(16)). IR

(in Nujol), ν/cm^–1: 1657 (C=O). MS, m/z (I_rel(%)): 309 [M]⁺

(9), 265 (21), 156 (32), 136 (100), 121 (31), 100 (79), 99 (36),

88 (27), 86 (88), 70 (38), 56 (64).

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

997

Table 5. Crystallographic characteristics and the Xꢀray diffraction data collection and refinement statistics for the

crystals of 4a,c and 5a,c

Compound

4a

4c

5a

5c

Molecular formula

М/g mol^–1

Crystal system

Space group

a/Å

b/Å

c/Å

α/deg

C

₁₄H₂₁NO₄

267.32

C₁₆H₂₃NO₅

309.35

Monoclinic

C2/c

24.774(4)

8.1343(11)

18.038(2)

90

C₁₄H₂₂N₂O₃

266.34

Monoclinic

P2₁/n

8.4832(4)

17.2639(8)

9.9592(5)

90

C₁₆H₂₄N₂O₄

308.37

Orthorhombic

P2₁2₁2₁

8.3151(7)

9.3885(8)

20.4825(18)

90

Orthorombic

Pca2₁

20.1308(6)

8.4639(3)

16.4133(6)

90

β/deg

90

118.517(3)

90

3194.0(8)

8

1.287

1328

109.0300(10)

90

1378.84(11)

4

90

γ/deg

V/Å³

2796.58(16)

8

1599.0(2)

4

1.281

Z

d_calc/g cm^–3

F(000)

1.270

1152

1.283

576

664

μ(MoꢀKα)/mm^–1

Crystal dimensions/mm

θ Scan mode/range, deg

Ranges of indices of

measured reflections

0.093

0.095

0.090

0.092

0.36×0.28×0.22

ω/2.02—29.00

–24 ≤ h ≤ 26,

–9 ≤ k ≤ 11,

–13 ≤ l ≤ 22

15701

0.26×0.23×0.18

ω/2.67—29.00

–33 ≤ h ≤ 27,

–11 ≤ k ≤ 11,

–23 ≤ l ≤ 24

9369

0.22×0.20×0.18

ω/2.36—29.00

–8 ≤ h ≤ 11,

–17 ≤ k ≤ 23,

–13 ≤ l ≤ 9

8959

0.42×0.36×0.32

ω/2.39—28.99

–11 ≤ h ≤ 10,

–12 ≤ k ≤ 5,

–14 ≤ l ≤ 27

7805

Number of measured

reflections

Number of independent

reflections

Number of reflections

5416

(R_int= 0.0287)

4769

4183

(R_int= 0.0352)

3028

3673

(R_int= 0.0197)

2995

4033

(R_int= 0.0220)

3561

with I > 2σ(I)

Number of refined

parameters

513

291

261

295

R factors based on

reflections with I > 2σ(I)

based on all reflections

R₁= 0.0332,

wR₂= 0.0788

R₁= 0.0419,

wR₂= 0.0826

1.052

R₁= 0.0506,

wR₂= 0.1143

R₁= 0.0742,

wR₂= 0.1227

1.012

R₁= 0.0364,

wR₂= 0.0933

R₁= 0.0473,

wR₂= 0.0982

1.059

R₁= 0.0346,

wR₂= 0.0785

R₁= 0.0435,

wR₂= 0.0823

1.050

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max)/e•Å^–3

–0.186/0.202

–0.269/0.344

–0.198/0.315

–0.188/0.216

(0.76 mL, 5.5 mmol) in anhydrous THF (50 mL) was kept

at room temperature for 7 days. Then the solvent was evaporated

in vacuo. Benzene (50 mL) was added to the residue. The mixꢀ

ture was washed with water (4×15 mL), the solvent was evapoꢀ

rated in vacuo, and the residue was extracted with boiling

heptane (3×40 mL). After evaporation of the extracts in vacuo,

diester 7d was obtained as a slightly yellowish viscous oil in a

yield of 0.92 g (90%). ¹H NMR, δ: 1.18 (t, 6 H, 2 Me, J = 7.1 Hz);

2.83 (t, 4 H, 2 CH₂N, J = 6.1 Hz); 3.01 (t, 4 H, 2 CH₂N, J = 4.8 Hz);

3.44 (s, 4 H, 2 CH₂CO₂); 3.54 (t, 4 H, 2 CH₂O, J = 6.1 Hz);

3.95 (t, 4 H, 2 CH₂OAr, J = 4.8 Hz); 4.06 (q, 4 H, 2 CH₂Me,

J = 7.1 Hz); 6.84 (m, 2 H, H(14), H(17)); 6.90 (m, 2 H, H(15),

H(16)). IR (in film), ν/cm^–1: 1734 (C=O). MS, m/z (I_rel(%)):

438 [M]⁺(3), 365 (85), 265 (93), 250 (40), 192 (47), 160 (100),

146 (55), 124 (41), 130 (88), 100 (46), 56 (59). Highꢀresolution

MS, Found: m/z 438.2364 [M]⁺. C₂₂H₃₄N₂O₇. Calculated:

M = 438.2366.

and a 5% excess of azacrown ether in MeCN (3—5 mL) with

benzene vapor at room temperature. The precipitates were

separated by decantation and dried in vacuo at 80 °C.

Complex 3a•4Ba(ClO₄)₂. The yield was 71%, colorless

crystals, m.p. >272 °C (with decomp.). Found (%): C, 11.97;

H, 1.84; N, 0.81. C₁₆H₂₅Ba₄Cl₈NO₃₆. Calculated (%): C, 11.72;

H, 1.54; N, 0.85.

Complex 4a•Ba(ClO₄)₂•0.25C₆H₆. The yield was 93%,

colorless crystals, m.p. >255 °C (with decomp.). Found (%):

C, 29.92; H, 3.80; N, 2.10. C_15.5H_22.5BaCl₂NO₁₂. Calcuꢀ

lated (%): C, 29.88; H, 3.64; N, 2.25. IR (in Nujol), ν/cm^–1

:

3391 (N—H).

Complex 4a•Pb(ClO₄)₂. The yield was 66%, colorless

crystals, m.p. 291—292 °C (with decomp.). Found (%): C, 25.15;

H, 3.20; N, 2.14. C₁₄H₂₁Cl₂NO₁₂Pb. Calculated (%): C, 24.97;

H, 3.14; N, 2.08.

Complex 4b•Ba(ClO₄)₂. The yield was 88%, colorless

crystals, m.p. 339—340 °C (with decomp.). Found (%): C, 29.11;

H, 3.69; N, 2.28. C₁₅H₂₃BaCl₂NO₁₂. Calculated (%): C, 29.17;

H, 3.75; N, 2.27.

Complexes of aza crown ethers with metal perchlorates were

precipitated by the slow saturation of a solution of a mixture

of NaClO₄, Ba(ClO₄)₂, or Pb(ClO₄)₂•3H₂O (~20—60 μmol)

998

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

Table 6. Crystallographic characteristics and the Xꢀray diffraction data collection and refinement statistics for the

crystals of 6a—c and 7a•H₂O

Compound

6a

6b

6c

7a•H₂O

Molecular formula

М/g mol^–1

Crystal system

Space group

a/Å

b/Å

c/Å

α/deg

β/deg

C

₁₄H₂₁NO₄

267.32

C₁₅H₂₃NO₄

281.34

Orthorhombic

Pbca

16.6030(16)

8.3768(8)

21.075(2)

90

C₁₆H₂₃NO₅

309.35

C₁₄H₂₄N₂O₄

284.35

Orthorhombic

Pbcn

36.9551(12)

9.0727(3)

9.2441(3)

90

Monoclinic

P2₁

10.6366(8)

8.5150(5)

15.8098(8)

90

105.328(2)

90

1380.97(15)

4

Triclinic

–

P1

8.0215(4)

9.2735(5)

10.8191(5)

90.031(2)

95.766(2)

98.946(2)

790.88(7)

2

90

γ/deg

V/Å³

2931.1(5)

8

1.275

3099.39(18)

8

Z

d_calc/g cm^–3

F(000)

1.286

576

1.299

332

1.219

1232

1216

μ(MoꢀKα)/mm^–1

Crystal dimensions/mm

θ Scan mode/range, deg

Ranges of indices of

measured reflections

0.094

0.092

0.096

0.089

0.26×0.20×0.16

ω/3.11—30.26

–14 ≤ h ≤ 14,

–12 ≤ k ≤ 11,

–22 ≤ l ≤ 22

12172

0.36×0.28×0.18

ω/1.93—29.00

–22 ≤ h ≤ 22,

–11 ≤ k ≤ 11,

–28 ≤ l ≤ 28

23325

0.20×0.16×0.14

ω/1.89—28.99

–10 ≤ h ≤ 10,

–12 ≤ k ≤ 12,

–14 ≤ l ≤ 13

5186

0.24×0.22×0.18

ω/2.20—29.00

–47 ≤ h ≤ 50,

–8 ≤ k ≤ 12,

–12 ≤ l ≤ 10

17057

Number of measured

reflections

Number of independent

reflections

Number of reflections

7575

(R_int= 0.0474)

6181

3892

(R_int= 0.0461)

2980

3853

(R_int= 0.0182)

3024

4081

(R_int= 0.0221)

3393

with I > 2σ(I)

Number of refined

parameters

351

273

291

278

R factors based on

reflections with I > 2σ(I)

based on all reflections

R₁= 0.1383,

wR₂= 0.3365

R₁= 0.1558,

wR₂= 0.3555

1.434

R₁= 0.0404,

wR₂= 0.1082

R₁= 0.0562,

wR₂= 0.1164

1.082

R₁= 0.0413,

wR₂= 0.0992

R₁= 0.0570,

wR₂= 0.1049

1.057

R₁= 0.0394,

wR₂= 0.0982

R₁= 0.0492,

wR₂= 0.1027

1.038

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max)/e•Å^–3

–0.423/2.458

–0.212/0.441

–0.192/0.288

–0.163/0.266

Complex 4d•Ba(ClO₄)₂. The yield was 64%, colorless

H, 3.71; N, 2.24. C₁₅H₂₃BaCl₂NO₁₂. Calculated (%): C, 29.17;

H, 3.75; N, 2.27.

crystals, m.p. 282—283 °C (with decomp.). Found (%): C, 31.14;

H, 3.94; N, 2.07. C₁₈H₂₇BaCl₂NO₁₄. Calculated (%): C, 31.35;

H, 3.95; N, 2.03. IR (in Nujol), ν/cm^–1: 1722 (C=O).

Complex 5b•Ba(ClO₄)₂. The yield was 85%, colorless

crystals, m.p. 345—347 °C (with decomp.). Found (%): C, 30.48;

H, 4.19; N, 4.43. C₁₆H₂₆BaCl₂N₂O₁₁. Calculated (%): C, 30.47;

H, 4.16; N, 4.44.

Complex 5b•Pb(ClO₄)₂. The yield was 73%, colorless

crystals, m.p. 259—261 °C (with decomp.). Found (%): C, 27.67;

H, 3.85; N, 4.09. C₁₆H₂₆Cl₂N₂O₁₁Pb. Calculated (%): C, 27.43;

H, 3.74; N, 4.00.

Complex 6a•Ba(ClO₄)₂. The yield was 81%, colorless

crystals, m.p. 312—313 °C (with decomp.). Found (%): C, 28.01;

H, 3.34; N, 2.26. C₁₄H₂₁BaCl₂NO₁₂. Calculated (%): C, 27.86;

H, 3.51; N, 2.32. IR (in Nujol), ν/cm^–1: 3312 (N—H).

Complex 6b•NaClO₄. The yield was 35%, white powder,

m.p. 160—163 °C. Found (%): C, 44.71; H, 5.71; N, 3.49.

C₁₅H₂₃ClNNaO₈. Calculated (%): C, 44.62; H, 5.74; N, 3.47.

Complex 6b•Ba(ClO₄)₂. The yield was 90%, white powder,

m.p. 293—296 °C (with decomp.). Found (%): C, 29.11;

Complex 6d•Ba(ClO₄)₂. The yield was 85%, colorless

crystals, m.p. 289—290 °C (with decomp.). Found (%): C, 31.38;

H, 3.87; N, 2.04. C₁₈H₂₇BaCl₂NO₁₄. Calculated (%): C, 31.35;

H, 3.95; N, 2.03. IR (in Nujol), ν/cm^–1: 1716 (C=O).

Complex 7b•Ba(ClO₄)₂. The yield was 94%, white powder,

m.p. 313—314 °C (with decomp.). Found (%): C, 30.51;

H, 4.19; N, 4.54. C₁₆H₂₆BaCl₂N₂O₁₁. Calculated (%): C, 30.47;

H, 4.16; N, 4.44.

Complex 7d•NaClO₄. The yield was 53%, yellowish

powder, m.p. 62—64 °C. Found (%): C, 47.24; H, 6.09; N, 5.04.

C₂₂H₃₄ClN₂NaO₁₁. Calculated (%): C, 47.11; H, 6.11; N, 4.99.

IR (in Nujol), ν/cm^–1: 1732 (C=O).

Complex 7d•Ba(ClO₄)₂. The yield was 74%, yellowish

powder, m.p. >115 °C (with decomp.). Found (%): C, 34.19;

H, 4.47; N, 3.58. C₂₂H₃₄BaCl₂N₂O₁₅. Calculated (%): C, 34.11;

H, 4.42; N, 3.62. IR (in Nujol), ν/cm^–1: 1713 (C=O).

Xꢀray diffraction study. Crystals of free azacrown ethers

were grown by the slow evaporation of their solutions in a

CH₂Cl₂—hexane mixture at room temperature. The crystalline

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

999

Table 7. Crystallographic characteristics and the Xꢀray diffraction data collection and refinement statistics for the

crystals of 4b•Ba(ClO₄)₂, 4d•Ba(ClO₄)₂, 7b•Ba(ClO₄)₂, and 8

Compound

4b•Ba(ClO₄)₂

4d•Ba(ClO₄)₂

7b•Ba(ClO₄)₂

8

Molecular formula

М/g mol^–1

Crystal system

Space group

a/Å

b/Å

c/Å

α/deg

β/deg

C

₁₅H₂₃BaCl₂NO₁₂

617.58

Monoclinic

P2₁/c

8.7311(14)

15.935(3)

15.306(2)

90

98.990(4)

90

C₁₈H₂₇BaCl₂NO₁₄C₁₆H₂₆BaCl₂N₂O₁₁

C₁₄H₂₁NO₄

267.32

689.65

Monoclinic

P2₁/c

630.63

Monoclinic

P2₁/n

Triclinic

–

P1

15.0987(9)

8.5917(5)

20.4014(12)

90

9.4114(5)

17.2171(9)

14.4367(7)

90

6.4366(4)

10.2180(7)

11.4097(7)

67.697(2)

86.696(2)

82.179(2)

687.80(8)

2

110.939(2)

90

100.5700(10)

90

γ/deg

V/Å³

2103.4(6)

4

1.950

2471.8(3)

4

2299.6(2)

4

Z

d_calc/g cm^–3

F(000)

1.853

1.822

1.291

288

1224

1376

1256

μ(MoꢀKα)/mm^–1

Crystal dimensions/mm

θ Scan mode/range, deg

Ranges of indices of

measured reflections

2.206

1.894

2.018

0.094

0.46×0.04×0.04

ω/1.86—28.00

–11 ≤ h ≤ 11,

–21 ≤ k ≤ 21,

–20 ≤ l ≤ 15

15540

0.42×0.22×0.08

ω/2.11—28.00

–17 ≤ h ≤ 19,

–11 ≤ k ≤ 11,

–26 ≤ l ≤ 26

13970

0.28×0.22×0.18

ω/1.86—30.57

–13 ≤ h ≤ 13,

–24 ≤ k ≤ 24,

–20 ≤ l ≤ 20

22843

0.14×0.12×0.10

ω/1.93—28.99

–8 ≤ h ≤ 6,

–13 ≤ k ≤ 9,

–15 ≤ l ≤ 8

4078

Number of measured

reflections

Number of independent

reflections

Number of reflections

5074

(R_int= 0.0562)

3778

5946

(R_int= 0.0406)

4513

7053

(R_int= 0.0243)

6566

3304

(R_int= 0.0196)

2268

with I > 2σ(I)

Number of refined

parameters

372

434

393

257

R factors based on

reflections with I > 2σ(I)

based on all reflections

R₁= 0.0355,

wR₂= 0.0814

R₁= 0.0614,

wR₂= 0.0907

1.042

R₁= 0.0324,

wR₂= 0.0690

R₁= 0.0537,

wR₂= 0.0757

1.017

R₁= 0.0286,

wR₂= 0.0590

R₁= 0.0313,

wR₂= 0.0599

1.201

R₁= 0.0465,

wR₂= 0.1108

R₁= 0.0731,

wR₂= 0.1216

1.035

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max)/e•Å^–3

–0.753/1.051

–1.108/1.326

–0.590/0.664

–0.241/0.219

complexes of benzoazacrown ethers with barium and sodium

perchlorates were prepared by the slow saturation of solutions

of the ligands and the salts in MeCN with benzene vapor as

described above.

7b•Ba(ClO₄)₂, and 9•NaClO₄, using a riding model for 6a

and 6d•Ba(ClO₄)₂, or using a mixed scheme (isotropically and

using a riding model) for 6a•Ba(ClO₄)₂. The hydrogen atoms

of the NH groups in molecules 4a, 5a,c, 6a, 7a•H₂O, and

6a•Ba(ClO₄)₂, the hydrogen atom of the OH group in molecule

8, and the hydrogen atoms of the solvent water molecules in

7a•H₂O and 5b•Ba(ClO₄)₂•0.5H₂O were located from differꢀ

ence Fourier maps and refined isotropically (with restraints on

the N—H bond length in 4a and 6a).

The structure of 6a was characterized by the relatively high

R factors because of high crystal mosaicity, which is apparently

the inherent property of this compound. We succeeded in

choosing only a few crystals with a relatively low content of an

impurity component, as evidenced by the high residual electron

density even for the bestꢀquality sample. Nevertheless, in spite

of the low accuracy of the structure solution, it can be stated

with assurance that the structural motif and the main geometric

parameters of both independent molecules 6a are reliable for a

Single crystals of azacrown ethers or their metal complexes

were mounted on a Bruker SMARTꢀCCD diffractometer under

a cold nitrogen stream (T = 190(2) K for 7b•Ba(ClO₄)₂and

120.0(2) K for the other crystals). The Xꢀray diffraction data sets

were collected using MoꢀKα radiation (λ = 0.71073 Å, graphite

monochromator). The Xꢀray data were processed with the use of

the SAINT program.²⁹For the crystals of all metal complexes,

absorption corrections were applied using the SADABS method.

All structures were solved by direct methods and refined by the

fullꢀmatrix leastꢀsquares method based on F²with anisotropic

displacement parameters for all nonhydrogen atoms. The

hydrogen atoms at the carbon atoms were positioned geometriꢀ

cally and refined isotropically for 4a,c, 5a,c, 6b,c, 7a•H₂O, 8,

4b•Ba(ClO₄)₂, 4d•Ba(ClO₄)₂, 5b•Ba(ClO₄)₂•0.5H₂O,

1000

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

Vedernikov et al.

Table 8. Crystallographic characteristics and the Xꢀray diffraction data collection and refinement statistics for the

crystals of 5b•Ba(ClO₄)₂•0.5H₂O, 6a•Ba(ClO₄)₂, 6d•Ba(ClO₄)₂, and 9•NaClO₄

Compound

5b•Ba(ClO₄)₂•0.5H₂O

6a•Ba(ClO₄)₂

6d•Ba(ClO₄)₂

9•NaClO₄

Molecular formula

М/g mol^–1

Crystal system

Space group

a/Å

b/Å

c/Å

α/deg

β/deg

C₁₆H₂₇BaCl₂N₂O_11.5C₁₄H₂₁BaCl₂NO₁₂C₁₈H₂₇BaCl₂NO₁₄C₁₇H₂₆ClN₂NaO₈

639.64

Tric_–linic

P1

603.56

Tric_–linic

P1

689.65

Monoclinic

P2₁/c

444.84

Monoclinic

P2₁/c

10.0303(8)

10.3858(8)

23.6537(19)

82.597(4)

79.106(4)

71.101(4)

2283.1(3)

4

11.9951(7)

14.0697(8)

15.3256(8)

115.317(2)

92.818(2)

113.811(2)

2060.7(2)

4

20.6668(7)

10.8212(4)

22.9762(9)

90

107.8800(10)

90

9.4634(8)

25.232(2)

9.3834(9)

90

112.588(3)

90

γ/deg

V/Å³

4890.2(3)

8

2068.7(3)

4

Z

d_calc/g cm^–3

F(000)

1.861

1.945

1.873

1.428

1276

1192

2752

936

μ(MoꢀKα)/mm^–1

Crystal dimensions/mm

θ Scan mode/range, deg

Ranges of indices of

measured reflections

2.036

2.250

1.915

0.252

0.12×0.08×0.06

ω/2.08—28.00

–13 ≤ h ≤ 13,

–13 ≤ k ≤ 13,

–31 ≤ l ≤ 31

27045

0.28×0.26×0.12

ω/1.93—28.00

–15 ≤ h ≤ 15,

–18 ≤ k ≤ 18,

–20 ≤ l ≤ 20

14184

0.50×0.40×0.04

ω/2.39—28.00

–27 ≤ h ≤ 27,

–13 ≤ k ≤ 14,

–29 ≤ l ≤ 27

27392

0.46×0.28×0.08

ω/2.84—29.00

–12 ≤ h ≤ 8,

–34 ≤ k ≤ 33,

–12 ≤ l ≤ 12

11920

Number of measured

reflections

Number of independent

reflections

Number of reflections

10655

(R_int= 0.0466)

8295

9243

(R_int= 0.0218)

7781

11578

(R_int= 0.0523)

8100

5355

(R_int= 0.0755)

2841

with I > 2σ(I)

Number of refined

parameters

802

672

649

367

R factors based on

reflections with I > 2σ(I)

based on all reflections

R₁= 0.0429,

wR₂= 0.1117

R₁= 0.0559,

wR₂= 0.1203

1.048

R₁= 0.0332,

wR₂= 0.0973

R₁= 0.0386,

wR₂= 0.1009

1.104

R₁= 0.0392,

wR₂= 0.0845

R₁= 0.0707,

wR₂= 0.0922

0.957

R₁= 0.0660,

wR₂= 0.1216

R₁= 0.1457,

wR₂= 0.1421

0.930

Goodnessꢀofꢀfit on F²

Residual electron density

(min/max)/e•Å^–3

–2.003/2.180

–0.945/1.888

–1.429/2.476

–0.381/0.522

comparison with the corresponding parameters of the other free

benzoazacrown ethers and the discussion of conformational

changes caused by the formation of the complex with Ba(ClO₄)₂.

All calculations were carried out with the use of the

SHELXTLꢀPlus program package.³⁰The crystallographic charꢀ

acteristics and the Xꢀray diffraction data collection and refineꢀ

ment statistics are given in Tables 5—8. The atomic coordinates

and other experimental data were deposited with the Cambridge

Crystallographic Data Centre;* the CCDC numbers 671441

(4a), 671443 (4c), 671445 (5a), 671447 (5c), 671449 (6a),

671450 (6b), 671451 (6c), 671453 (7a•H₂O), 671454 (8),

671442 (4b•Ba(ClO₄)₂), 671444 (4d•Ba(ClO₄)₂), 671446

(5b•Ba(ClO₄)₂•0.5H₂O), 671448 (6a•Ba(ClO₄)₂), 671452

(6d•Ba(ClO₄)₂), 683509 (7b•Ba(ClO₄)₂), and 671455

(9•NaClO₄).

¹H NMR titration. In the experiments, MeCNꢀd₃was

used as the solvent (the water content <0.05%, FGUP RNTs

Prikladnaya khimiya, St. Petersburg). The compositions and the

stability constants of the complexes of benzoazacrown ethers

with the salts M^m+(ClO₄

) were determined by analyzing the

–

changes in the positions of ^mthe signals for protons of the ligands

(L) depending on the concentration of the salt in the case of

direct titration or the concentration of the competitive ligands

(L^c) in the case of competitive titration. In the case of direct

titration, the concentration of the salts was varied from 0 to

0.015—0.08 mol L^–1, the total concentration of L being

unchanged (~5•10^–3mol L^–1). In the case of competitive titraꢀ

tion, the concentrations of L and the salts remained unchanged

(~5•10^–3and 6•10^–3mol L^–1, respectively), and the concenꢀ

tration of L^cwas varied from 0 to 0.03—0.1 mol L^–1. The crown

ethers, whose signals in the spectrum overlap with the signals of

L only slightly and for which the stability constants of the correꢀ

sponding complexes with these ligands were determined, were

* CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax: (+44)

1223 33 6033; eꢀmail: deposit@ccdc.cam.ac). The data can be

obtained from the authors.

used as L^c. The ligands L^care given in Tables 3 and 4. The Δδ

H

Benzoazacrown ethers and their complexes

Russ.Chem.Bull., Int.Ed., Vol. 58, No. 5, May, 2009

1001

values were measured with an accuracy of 0.001 ppm. The staꢀ

bility constants of the complexes were calculated with the use of

the HYPNMR program.³¹

14. J. C. Lockhart, A. C. Robson, M. E. Thompson, S. D. Furtado,

C. K. Kaura, A. R. Allan, J. Chem. Soc., Perkin Trans. 1,

1973, 577.

15. C. J. Pedersen, M. H. Bromels, US Pat. 3847949 (1974);

Chem. Abstrs, 1975, 82, 73049.

16. J. R. Blackborow, J. C. Lockhart, D. E. Minnikin, A. C.

Robson, M. E. Thompson, J. Chromatogr., 1975, 107, 380.

17. C. R. Landis, R. A. Sawyer, E. Somsook, Organometallics,

2000, 19, 994.

18. J. Jurczak, T. Stankiewicz, P. Salanski, S. Kasprzyk,

P. Lipkowski, Tetrahedron, 1993, 49, 1478.

19. J. Jurczak, R. Ostaszewski, Tetrahedron Lett., 1988, 29, 959.

20. L. C. Hodgkinson, I. O. Sutherland, J. Chem. Soc., Perkin

Trans. 1, 1979, 1908.

We thank O. V. Tikhonova, D. S. Spiridonov, E. A.

Fedorchuk, and O. V. Eshcheulova for help in the synꢀ

thesis of benzoazacrown ethers.

This study was financially supported by the Russian

Foundation for Basic Research (Project Nos 06ꢀ03ꢀ32456

and 06ꢀ03ꢀ33162), the Presidium of the Russian Academy

of Sciences (Program No. 8), the Ministry of Education

and Science of the Russian Federation, and the Royal

Society of Chemistry (Great Britain, Personal Grants for

L. G. Kuz´mina and J. A. K. Howard).

21. O. A. Fedorova, A. I. Vedernikov, I. E. Baronova, O. V.

Eshcheulova, E. A. Fedorchuk, K. Gloe, S. P. Gromov,

Izv. Akad. Nauk, Ser. Khim., 2004, 381 [Russ. Chem. Bull.,

Int. Ed., 2004, 53, 396].

References

22. W. Clegg, P. J. Cooper, J. C. Lockhart, Acta Crystallogr.,

Sect. C, 1996, 52, 1795.

23. P. Pniewska, T. Stankiewicz, J. Jurczak, J. Chem. Crystallogr.,

1995, 25, 75.

1. C. J. Pedersen, J. Am. Chem. Soc., 1967, 89, 7017.

2. M. Hiraoka, Crown Compounds. Their Characteristics

and Applications, Kodansha—Elsevier, Tokyo—Amsterdam—

Oxford—New York, 1982.

3. K. E. Krakowiak, J. S. Bradshaw, D. J. ZameckaꢀKrakowiak,

Chem. Rev., 1989, 89, 929.

4. J. S. Bradshaw, K. E. Krakowiak, R. M. Izatt, Azaꢀcrown

Macrocycles, Ed. E. C. Taylor, J. Wiley and Sons, New York,

1993, 885 pp.

5. S. P. Gromov, S. N. Dmitrieva, M. V. Churakova, Usp.

Khim., 2005, 74, 503 [Russ. Chem. Rev. (Engl. Transl.), 2005,

74, 461].

6. M. V. Alfimov, S. P. Gromov, Applied Fluorescence in

Chemistry, Biology and Medicine, Eds W. Rettig, B. Strehmel,

S. Schrader, H. Seifert, SpringerꢀVerlag, Berlin, 1999, 161.

7. S. FeryꢀForgues, F. AlꢀAli, J. Photochem. Photobiol. C:

Photochem. Rev., 2004, 5, 139.

8. N. A. Lobova, Ph. D. (Chem.) Thesis, Photochemistry

Center of the Russian Academy of Sciences, Moscow, 2007

(in Russian).

9. A. Ya. Freidzon, A. A. Bagatur´yants, S. P. Gromov, M. V.

Alfimov, Int. J. Quantum Chem., 2004, 100, 617.

10. S. P. Gromov, S. N. Dmitrieva, A. I. Vedernikov, M. V.

Churakova, Izv. Akad. Nauk, Ser. Khim., 2004, 1362 [Russ.

Chem. Bull., Int. Ed., 2004, 53, 1417].

11. S. P. Gromov, S. N. Dmitrieva, A. I. Vedernikov, L. G.

Kuz´mina, A. V. Churakov, Yu. A. Strelenko, J. A. K. Howard,

Eur. J. Org. Chem., 2003, 3189.

24. A. I. Vedernikov, S. S. Basok, S. P. Gromov, L. G. Kuz´mina,

V. G. Avakyan, N. A. Lobova, E. Yu. Kulygina, T. V. Titkov,

Yu. A. Strelenko, E. I. Ivanov, J. A. K. Howard, M. V.

Alfimov, Zh. Org. Khim., 2005, 41, 864 [Russ. J. Org. Chem.

(Engl. Transl.), 2005, 41, 843].

25. L. G. Kuz´mina, A. I. Vedernikov, S. N. Dmitrieva, J. A. K.

Howard, S. P. Gromov, Izv. Akad. Nauk, Ser. Khim., 2007,

967 [Russ. Chem. Bull., Int. Ed., 2007, 56, 1003].

26. S. N. Dmitrieva, Ph. D. (Chem.) Thesis, Photochemistry

Center of the Russian Academy of Sciences, Moscow, 2003

(in Russian).

27. E. N. Ushakov, L. G. Kuz´mina, A. I. Vedernikov, M. S.

Kapichnikova, J. A. K. Howard, M. Worner, A. M. Braun,

M. V. Alfimov, S. P. Gromov, Izv. Akad. Nauk, Ser. Khim.,

2006, 90 [Russ. Chem. Bull., Int. Ed., 2006, 55, 94].

28. U. Lüning, M. Müller, M. Gelbert, K. Peters, H. G. von

Schnering, M. Keller, Chem. Ber., 1994, 127, 2297.

29. SAINT, Version 6.02A, Bruker AXS Inc., Madison, Wisconsin

(USA), 2001.

30. SHELXTLꢀPlus, Version 5.10, Bruker AXS Inc., Madison,

Wisconsin (USA), 1997.

31. C. Frassineti, S. Ghelli, P. Gans, A. Sabatini, M. S. Moruzzi,

A. Vacca, Anal. Biochem., 1995, 231, 374.

12. V. G. Avakyan, S. P. Gromov, A. I. Vedernikov, S. N.

Dmitrieva, M. V. Alfimov, Izv. Akad. Nauk, Ser. Khim.,

2004, 25 [Russ. Chem. Bull., Int. Ed., 2004, 53, 24].

13. S. P. Gromov, S. N. Dmitrieva, M. V. Churakova, A. I.

Vedernikov, N. A. Kurchavov, L. G. Kuz´mina, N. A. Kataeva,

J. A. K. Howard, Zh. Org. Khim., 2004, 40, 1247 [Russ. J.

Org. Chem. (Engl. Transl.), 2004, 40, 1200].

Received December 26, 2007;

in revised form May 28, 2008

Article Doi

Benzoaza-15-crown-5 ethers: Synthesis, structure, and complex formation with metal and ethylammonium ions

DOI: 10.1007/s11172-009-0127-y

Source and publish data:

Authors:

Article abstract of DOI:10.1007/s11172-009-0127-y

Full text of DOI:10.1007/s11172-009-0127-y

Products guided by the article

R&D Labs maybe for 41536-52-1

Relevant to this article

Hot Product