N-Methylbenzoazacrown ethers with the nitrogen atom conjugated with the benzene ring: The improved synthesis and the reasons for the high stability of complexes with metal and ammonium cations

Article abstract of DOI:10.1002/poc.1527

An improved method for the synthesis of formyl derivatives of N - Methylbenzoazacrown ethers is proposed. They are prepared in up to 68% yields over fewer steps and with a much shorter time required for the last step. The stability constants of complexes formed by N-methylbenzoazacrown ethers and their structural analogs with alkali metal, alkaline - Earth metal and ammonium cations were determined by ¹H NMR titration in CD₃CN. High stability of complexes of N-methyl derivatives of benzoazacrown ethers is demonstrated, comparable with or even exceeding the stability of benzocrown-ether complexes and markedly exceeding the stability of complexes of phenylazacrown ethers with the same macrocycle size. The structures of azacrown ethers and their complexes with Ba(ClO₄)₂ were studied by X-ray diffraction. A high degree of pre-organization of N - Methylbenzoazacrown ethers toward the formation of complexes with metal and ammonium cations was noted, which is due to the clear-cut pyramidal geometry of the nitrogen atom and the orientation of the lone electron pairs (LEPs) of most heteroatoms towards the centre of the macroheterocycle. Copyright

Full text of DOI:10.1002/poc.1527

Research Article
Received: 11 July 2008,
Revised: 12 December 2008,
Accepted: 5 January 2009,
Published online in Wiley InterScience: 25 February 2009
(www.interscience.wiley.com) DOI 10.1002/poc.1527
N-Methylbenzoazacrown ethers with the
nitrogen atom conjugated with the benzene
ring: the improved synthesis and the reasons
for the high stability of complexes with metal
and ammonium cations
a
a
a
*
Sergey P. Gromov , Svetlana N. Dmitrieva , Artem I. Vedernikov ,
Nikolay A. Kurchavova, Lyudmila G. Kuz’minab, Yuri A. Strelenkoc,
Michael V. Alfimova and Judith A. K. Howardd
An improved method for the synthesis of formyl derivatives of N-methylbenzoazacrown ethers is proposed. They are
prepared in up to 68% yields over fewer steps and with a much shorter time required for the last step. The stability
constants of complexes formed by N-methylbenzoazacrown ethers and their structural analogs with alkali metal,
alkaline-earth metal and ammonium cations were determined by 1H NMR titration in CD3CN. High stability of
complexes of N-methyl derivatives of benzoazacrown ethers is demonstrated, comparable with or even exceeding the
stability of benzocrown-ether complexes and markedly exceeding the stability of complexes of phenylazacrown
ethers with the same macrocycle size. The structures of azacrown ethers and their complexes with Ba(ClO4)2 were
studied by X-ray diffraction. A high degree of pre-organization of N-methylbenzoazacrown ethers toward the
formation of complexes with metal and ammonium cations was noted, which is due to the clear-cut pyramidal
geometry of the nitrogen atom and the orientation of the lone electron pairs (LEPs) of most heteroatoms towards the
centre of the macroheterocycle. Copyright ß 2009 John Wiley & Sons, Ltd.
Supporting information may be found in the online version of this article.
Keywords: benzoazacrown ethers; complex formation; metal and ammonium cations; stability
of two fragments and inaccessibility of podands for intramole-
cular cyclization.[10–12] The new strategy we develop[13–15] for the
INTRODUCTION
An important feature of crown compounds is the ability to form
stable complexes with metal ions, organic cations and neutral
polar molecules. This ability underlies the use of crown
compounds as selective ligands for metal cations, in particular,
for extraction,[1,2] in ion-selective electrodes[3] and in photosen-
sitive systems.[4–9] Of particular interest from the standpoint of
using crown fragments in photosensitive ligands are those crown
compounds in which the nitrogen atom occurs in conjugation
with the chromophore. These azacrown compounds absorb at
markedly longer wavelengths than crown-ether derivatives; this
is especially important for the photometric and fluorescence
analysis, for photocontrolled extraction and ion transport
through membranes and for the design of photosensitive
molecular devices. Currently, phenylazacrown-ether derivatives
are used most widely for these purposes; however, they suffer
from a substantial drawback, in particular, their complexation
constants with metal ions are relatively low. In this respect,
benzoannelated derivatives of azacrown ethers can have
substantial advantages. The chemistry of 1-aza-2,3-benzocrown
ethers has been poorly developed until recently due to the
difficulty of the synthesis of these compounds by condensation
synthesis of functional derivatives of azacrown ethers in which
nitrogen is conjugated with the benzene ring by stepwise
transformation of readily available benzocrown ethers is a
promising alternative to the existing methods of synthesis of
*
Correspondence to: S. P. Gromov, Photochemistry Centre, Russian Academy of
Sciences, 7A Novatorov str., Moscow 119421, Russia.
E-mail: gromov@photonics.ru
a
b
c
d
S. P. Gromov, S. N. Dmitrieva, A. I. Vedernikov, N. A. Kurchavov, M. V. Alfimov
Photochemistry Centre, Russian Academy of Sciences, 7A Novatorov str.,
Moscow 119421, Russia
L. G. Kuz’mina
N. S. Kurnakov Institute of General and Inorganic Chemistry, Russian
Academy of Sciences, 31 Leninskiy prosp., Moscow 119991, Russia
Y. A. Strelenko
N. D. Zelinskiy Institute of Organic Chemistry, Russian Academy of Sciences,
47 Leninskiy prosp., Moscow 119991, Russia
J. A. K. Howard
Chemistry Department, Durham University, South Road, Durham DH1 3LE,
UK
J. Phys. Org. Chem. 2009, 22 823–833
Copyright ß 2009 John Wiley & Sons, Ltd.

S. P. GROMOV ET AL.
1-aza-2,3-benzocrown ethers. As regards the use in the synthesis
of photosensitive compounds, of most interest are benzoaza-
crown ethers 1a–c, which contain formyl substituent in the
benzene fragment in the para-position to nitrogen (Scheme 1).
This communication presents an improved synthesis of formyl
derivatives of N-methylbenzoazacrown ethers 1a–c with 12-, 15-
and 18-membered macrocycles. Comparative study of structures
1 and related compounds and their complexes with metal and
ammonium cations by 1H NMR and X-ray diffraction analysis were
carried out. The stability constants of the complexes of
benzoazacrown ethers 1b,c and their structural analogs were
determined in order to demonstrate the scope of using
compounds 1 as efficient macrocyclic ligands.
RESULTS AND DISCUSSION
Synthesis
Previously, we showed[16] that heating of formylbenzocrowꢀn
ethers 2a–c with an ethanol solution of MeNH2 and MeNHþ3 Cl
affords nitrogen-containing podands 3a–c in 66–80% yields. To
cyclize podands 3 to benzoazacrown ethers 1, the hydroxy
groups of 3a–c were replaced by chlorine and iodine,[14] i.e. by
easily leaving groups. This gave chloro 4a–c and iodo derivatives
5a–c of podands in yields of up to 97%. We studied cyclization of
the resulting iodo derivatives 5a–c in the absence of bases and in
the presence of weak bases, such as alkali metal carbonates.[14]
Under the action of weak bases, this gave mixtures of azacrown
compounds 1 and 6 with markedly pre-dominating N-methyl
derivatives 1a–c (Scheme 2). In the absence of bases,
N-demethylated benzoazacrown ethers 6a–c were formed as
the major or even the only products. Despite the rather high
yields of the target compounds 1, this method has substantial
drawbacks, in particular, the formation of product mixtures and
long cyclization time (150 h). In addition, the reaction does not go
to completion.
In order to optimize the synthesis of the formyl derivatives of
N-methylbenzoazacrown ethers 1a–c (to reduce the cyclization
time and the number of synthetic steps), we studied the reactivity
of chloro and iodo derivatives of azapodands 4a–c and 5a–c
under the action of a stronger base than alkali metal carbonates,
specifically, sodium hydride; this gave N-methylbenzoazacrown
ethers 1a–c in high yields and over short periods of time
(Scheme 3, Table 1).
Scheme 1. General approach to the synthesis of formyl derivatives of
N-methylbenzoazacrown ethers 1a–c
cyclization of chloride 4a barely proceeds under these conditions.
The cyclization of iodides 5a–c to 1a–c induced by NaH in THF
with heating proceeds even faster (for 30 min) than that of
chlorides 4a–c, giving products in equally good yields,
irrespective of the macrocycle size (57–68%). The cyclization of
iodides 5a–c occurs also at room temperature but over a longer
period. In this case, the yields of 1 somewhat decrease. The
obtained data suggest that NaH-induced cyclization of chloro
and iodo azapodands proceeds through the formation of the
reactive arylamide anion 7 (Scheme 3). This is indicated, first of all,
by the substantial shortening of the cyclization time compared to
that in the presence of alkali metal carbonates in acetonitrile. In
the latter case, the cyclization is due to the intramolecular
N-alkylation giving rise to the macrocyclic ammonium salt.[14]
Advantages of conducting the cyclization of halides under the
action of NaH in THF include good yields of the target products 1,
short reaction time and the possibility of preparing individual
It was found that on heating with NaH in dry THF, chlorides 4b,c
cyclize to give N-methylbenzoazacrown ethers 1b and 1c over
periods of 5.5 and 17 h in 59 and 27% yields, respectively. The
Scheme 2. Synthesis of benzoazacrown ethers 1a–c and 6a–c under the action of metal carbonates
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Copyright ß 2009 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 823–833

SYNTHESIS AND COMPLEXATION OF N-METHYLBENZOAZACROWN
Scheme 4. Synthesis of N-methylbenzoazacrown ether 1c from benzoa-
zacrown ether 6c The structures of all the obtained compounds were
proved by 1H NMR spectroscopy
iodide under the action of NaH in THF (Scheme 4). The reaction
was fast and gave 1c in 58% yield. This reaction demonstrates the
possibility of preparing, if necessary, N-alkyl derivatives of
benzoazacrown ethers.
Scheme 3. Synthesis of benzoazacrown ethers 1a–c under the action of
strong base
Stability of complexes
compounds and reducing the total number of steps in the case of
synthesis of benzoazacrown ether 1b.
Previously, we demonstrated[14] that refluxing of N-methyl
derivative 1c with dilute acetic acid gives rise to N-demethylated
product 6c. In this study, we carried out methylation of
compound 6c at the macrocycle nitrogen atom with methyl
Previously, we showed[14] that benzoazacrown ethers 1a–c and
6a–c form ‘host-guest’ complexes with Ca2þ ions in acetonitrile.
The complexation induces pronounced changes in the positions
of the 1H, 13C and 15N NMR signals, which indicates that the
calcium cation resides in the macrocycle cavity. It was of interest
to determine, under comparable conditions, the quantitative
characteristics for the stability of complexes of compounds 1 with
Group I and II metal ions and ammonium ions, to elucidate
the structural features of the complexes formed and the
selectivity with respect to various ions and to compare
the complexation capacities of benzoazacrown ethers and
related compounds.
Table 1. Cyclization of halides 4a–c and 5a–c into benzoa-
zacrown ethers 1a–c under the action of NaH in THFa
The ability of benzoazacrown ethers 1b,c to form complexes
with metal and ammonium perchlorates was estimated
quantitatively by 1H NMR titration in CD3CN. In most cases,
the procedure of direct titration was used, which consists in
adding Mmþ(ClO4ꢀ)m [Mmþ is the metal or ammonium cation
(m ¼ 1, 2)] in portions to the studied ligand.
Initial
halide
Reaction
time (h)
Benzoazacrown
ether
Yield
of 1 (%)
4a
4b
4c
5a
100
5.5
17
0.5
72b
0.5
24b
0.5
19b
1a
1b
1c
1a
5c
59
27
68
61
63
61
57
51
In those cases where the magnitude of the constant exceeded
the upper limit of applicability of the direct titration (K > 105 Mꢀ1),
the competitive 1H NMR titration was used. In this case, an
appropriate competing ligand was added in portions to a
complex of the studied ligand. The stability constant of the
complex formed by the competing ligand had been preliminarily
measured and the proton NMR signals of this ligand did
not overlap significantly with the signals of the ligand to be
studied.
5b
5c
1b
1c
a 64 8C.
b Ambient temperature.
c The yield of 1a was found from the 1H NMR spectrum of the
reaction mixture which contained 1a and 4a (9%). The yield of
1a was calculated with respect to converted 4a.
A representative example of the changes of proton signal
positions, which were observed in the system 1c/NH4ClO4, is
shown in Fig. 1. During this direct titration, all of 1H signals of the
ligand demonstrated monotonic changes with increasing salt/1c
J. Phys. Org. Chem. 2009, 22 823–833
Copyright ß 2009 John Wiley & Sons, Ltd.
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S. P. GROMOV ET AL.
Table 2.
Figure 1. Values of DdH ¼ dH(1c/NH4ClO4 mixture) – dH(free 1c) for some
protons of 1c in CD3CN as a function of the NH4ClO4/1c concentration
ratio
concentration ratio, indicating complex formation. The presence
of ammonium ion in the crown-ether cavity entails downfield
shifts of the signals of most protons (by DdH ¼ 0.08–0.14 ppm). An
especially great downfield shift (DdH upto 0.33 ppm) is found for
the signal of the CH(3) proton located in the ortho-position
relative to the nitrogen atom (as shown atom numbering in
Scheme 1). Apparently, this reflects switching of lone electron
pair (LEP) of the nitrogen atom from conjugation with the
benzene ring to hydrogen bond formation with the NHþ4 ion.
Conversely, the proton signals of the MeN and CH2N groups shift
upfield upon complexation (DdH upto ꢀ0.22 ppm). This might be
due to the overall effect of the change in the macrocycle
conformation on binding to the cation and to the increase in the
contribution of the sp3 hybridization for the nitrogen atom (as
shown below X-ray diffraction). These features are characteristic
of all the studied azacrown compounds on complexation with all
metal and ammonium cations, being more pronounced for
doubly charged cations than for monovalent ones. Complex
formation of model benzocrown ethers 2b,c and 8 induced
downfield shifts for all of their proton signals, excluding the cases
of complexes having 2(L):1(Mmþ) stoichiometry (as shown
below), where L is the crown compound.
The presence of the formyl group in the crown compounds
results in lower stability constants of the complexes due to the
electron-withdrawing nature of the substituent.[18] Comparison
of the data for benzo-15-crown-5 ether (8) and its formyl
derivative 2b shows an up to 20-fold decrease in the stability of
complexes with any of the cations. In addition, the complexation
capacity of the crown compounds studied depends on the
Table 2. Stability constants of the complexes formed by
crown ethers 1b,c, 2b,c, 6c, 8, 9a,b with metal, ammonium
and ethylammonium perchloratesa
logK1 (logK2)
Ligand Naþ
Kþ
Ca2þ
Ba2þ
NHþ4 EtNHþ3
8
ꢂ5 3.2 (1.9) 5.6b 5.4 (5.1)b
2.1
2.4
4.8b
The curves for the variation of the proton chemical shifts of the
ligand vs. the amount of the salt added (or the amount of the
competing ligand added) were used to calculate the stability
constants of the complexes by the HYPNMR program;[17] the
2b
1b
3.5
3.2
2.9 (2.5)
2.2
4.3
ꢃ5
4.4 (4.2)
4.6 (2.5)
2.0
2.0
2.2
1.7
5.3b
2.4
results fit well into the scheme of formation of 1(L):1(Mmþ
complexes:
)
9a
2c
1.6
>5
5.2c
4.8
0.6
3.7
1.9
7.0d
0.7
4.3
0.6
3.8
8.4e
1c
4.3
ꢃ5
8.0e
4.7b
4.8b
6.8d
4.1
3.7
K1
mþ
L þ Mmþ ðL ꢁ MÞ
(1)
!
where K1 (Mꢀ1) is the stability constant for 1:1 complexes. In the
case of metal cations with a large ionic radius, the possibility of
formation of 2(L):1(Mmþ) sandwich complexes was also taken into
account:
6c
9b
3.3
3.4
2.8
2.3
4.9
ꢂ5
2.5
1.9
2.0
1.6
4.9b
a 1H NMR titration in CD3CN, 30 8C. The total measurement
errors of the stability constants were ꢂ20% for the direct
titrations and ꢂ30% for competitive ones.
K1
mþ
mþ
!
ðL ꢁ MÞ þ L ðL2 ꢁ MÞ
(2)
where K2 (Mꢀ1) is the stability constant of the 2:1 complex. For
comparison, the ability to form complexes with these salts was
studied for a number of closely related structural analogs of
benzoazacrown ethers, namely, benzocrown ethers 2b,c, 8 and
N-phenylazacrown ethers 9a,b. The results are summarized in
1
b From competitive H NMR titration with compound 2b.
1
c From competitive H NMR titration with compound 1c.
1
d From competitive H NMR titration with compound 9b.
1
e From competitive H NMR titration with compound 8.
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Copyright ß 2009 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 823–833

SYNTHESIS AND COMPLEXATION OF N-METHYLBENZOAZACROWN
nature, the size and the charge of the cation, the macrocycle size
and the degree of conjugation of nitrogen with the benzene ring.
Representatives of 15-crown-5 and 18-crown-6 compounds
form more stable complexes with smaller-size cations (both for
the alkali metals and for alkaline-earth metals studied) and more
stable complexes with NH4þ ions than with EtNHþ3 . For doubly
charged cations, the stability constants of the complexes are
substantially (102–104 times) higher than similar values for
monovalent cations. Evidently, the higher charge density on
smaller metal cations or on doubly charged cations compared to
singly charged cations and the absence of electron-donating
substituents in NHþ4 promote stronger ion-dipole interactions
between the macrocycle heteroatoms and the cation located in
its cavity. The much higher stability of complexes of all
15-crown-5 compounds with Naþ ions compared with the
complexes with Kþ ions confirms also the classical view on the
necessity of size correspondence between the crown-ether cavity
and the metal ion for stronger binding of the ligand and the
substrate. It is noteworthy, however, that this view proved
inapplicable to all the 18-crown-6 compounds for which a better
correspondence between the macrocycle and cation geometric
sizes would be expected for potassium ions.
It was found that Ba2þ ions also form sandwich complexes
2(L):1(Ba2þ) with benzo-15-crown-5 compounds 1b, 2b and 8
owing to large size of the metal cation. However, the structures of
the sandwich complexes are different. In the case of crown ethers
2b and 8, ligands are preferably arranged in such a way that two
RC6H3(OCH2)2 fragments (R ¼ H, CHO) are located closely to each
other and their 1H NMR signals are shifted upfield with respect to
those in free ligands owing to mutual shielding. For benzoaza-
crown ether 1b, all types of proton signals of both the sandwich
and 1:1 complexes shift in the same direction. Apparently, the
methyl substituent at the nitrogen atom in 1b creates steric
hindrance preventing the two aromatic fragments from
approaching each other; therefore, in complex 2(1b):1(Ba2þ),
they point most likely to opposite directions, as shown in Fig. 2.
The conclusion concerning the less favourable arrangement of
the ligands in the sandwich complex 2(1b):1(Ba2þ) is also
supported by the K2 value being two orders of magnitude lower
than K1, which was not observed for the sandwich complexes of
2b and 8. With potassium ion, the last two compounds also form
sandwich complexes similar in structure to complex 2(1b):1(Ba2þ
)
but markedly less stable. The stability constants of the possible
sandwich complexes of 1b with the Kþ ion and 9a with the Kþ
and Ba2þ ions are apparently so low (logK2 < 0.5) that the
1
complexes cannot be detected by H NMR.
The stability constants of the complexes of 18-crown-6
compounds are 1.5–4 order of magnitude higher than those
of analogous 15-crown-5 compounds, which is attributable to the
larger number of donor heteroatoms in 18-membered crown
compounds than in 15-membered compounds.
The remarkable feature of new N-methyl derivatives of
benzoazacrown ethers 1b,c is the formation of substantially more
stable complexes with any of the cations studied compared with
their closest structural analogs, phenylazacrown ethers 9a,b
(Table 2). This feature is due to the specific properties of the
tertiary nitrogen atom in 1b,c, in which the LEP is essentially
eliminated from the conjugation with the benzene ring and,
therefore, it can be efficiently donated for the formation of the
coordination bond with the metal or ammonium cation.
Conversely, as shown by our X-ray diffraction studies (as shown
below), the geometric characteristics of nitrogen in 9a,b imply a
high degree of its conjugation with the benzene ring. Together with
the higher flexibility of the macrocycles of phenylazacrown ethers,
this feature makes these compounds less efficient ligands.[19,20]
A
similar effect was observed[14] for benzoaza-18-crown-6 ether 6c
whose secondary nitrogen atom is efficiently conjugated with the
benzene ring. The effect of the more rigid structure of the
macrocycle in 6c compared to 9b is, apparently, leveled by the
hydrogen atom of the NH group pointing toward the macro-
heterocycle centre;[14] therefore, compounds 6c and 9b demon-
strated almost equal abilities to bind metal and ammonium cations
(Table 2). One more notable fact deserves attention, namely, the
complexing capacity of 1b,c is comparable with and, in some cases,
is even higher than the ability of the analogs with only oxygen
atoms, namely, benzocrown ethers 2b,c to bind the same cations.
Thus, the quantitative measurements we carried out clearly
revealed the high complexation efficiency for the N-methyl
derivatives of benzoazacrown ethers 1 with respect to various
metal cations and ammonium ions, which is comparable to that
of benzocrown ethers and substantially exceeds that of
phenylazacrown ethers.
X-ray diffraction study
To understand the reasons for the higher complexing
ability of N-methylbenzoazacrown compounds compared to
N-phenylazacrown ethers we carried out X-ray diffraction studies
for some of the compounds and their metal complexes. Figure 3
shows a general view and atom labelling scheme of molecule 1b.
Selected bond lengths and angles for 1b are given in Table 1S
(refer to Supplementary Material (SM) to this article).
Figure 2. Proposed structures of sandwich complexes of benzocrown
ethers 1b, 2b and 8. This figure is available in colour online at www.
interscience.wiley.com/journal/poc
In 1b, some angular distortions at the C(7) atom bearing the
O(1) oxygen atom are found. Two O(1)—CAr—CAr angles are
J. Phys. Org. Chem. 2009, 22 823–833
Copyright ß 2009 John Wiley & Sons, Ltd.
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S. P. GROMOV ET AL.
Figure 4. Orientation of the LEP of the heteroatoms in the crown ether
moiety of 1b; lone pairs are depicted as full lines and denoted as E. The
lone pair of the O(1) on the 2p orbital involved in conjugation with the
p-system of the benzene ring and the hydrogen atoms are omitted for
clarity. This figure is available in colour online at www.interscience.
wiley.com/journal/poc
Figure 3. Structure of 1b. Here and in Figs 5–9, all non-hydrogen atoms
are shown at 50% probability of their thermal anisotropic displacement
parameters. This figure is available in colour online at www.interscience.
wiley.com/journal/poc
different, the internal one, O(1)—C(7)—C(2), being reduced to
116.0(1)8 compared to the other bond angle O(1)—C(7)—C(6),
equal to 123.3(1)8. The O(1) atom has an sp2 hybridization state,
which is evident from the C(7)—O(1)—C(8) bond angle
[117.4(1)8], which is greater than the bond angles at the other
crown-ether oxygens [113.5(1)–114.1(1)8] having an sp3 hybrid-
ization state. It should be noted that this kind of angular
distortion is opposite to that possibly resulting from a steric
repulsion between the O(1) and N(1) atoms. We believe that the
reason for the geometric feature of molecule 1b to be discussed
is conjugation between the benzene ring and the O(1) atom.
Actually, the C(8)—O(1)—C(7)—C(6) torsion angle (1.18) is
appropriate for the conjugation of a LEP of the oxygen atom
occupying the 2p orbital. This conjugation is accomplished in
spite of an essential steric hindrance between the alkyl atom C(8)
and the nearest C(6)—H fragment of the benzene ring; the
orientation in the flexible crown ether upon coordination to a
metal cation.
In order to compare the geometry of N-methylbenzoazacrown
ethers with that of N-demethylated azacrown ethers, we discuss
here the X-ray structure of benzoaza-15-crown-5 ether 10. This
compound was found upon repeated crystallization of azacrown
ether 6b and appeared to be a carboxyl rather than a formyl
derivative. Apparently, the carboxyl group in 10 has resulted from
air oxidation of the formyl group in 6b. Most likely, formyl and
carboxyl groups have nearly the same influence on the electron
density distribution in the benzene ring and the macrohetero-
cycle conformation. For this reason, we included the data on
structure 10 in our discussion and comparison.
Compound 10 contains a solvation molecule of dichloro-
methane; the molecular structure is shown in Fig. 5. Selected
bond lengths and angles for 10 are given in Table 2S (SM). In 10,
the O(1) oxygen atom located most closely to the benzene ring
has the sp2 hybridization; the bond angle at this oxygen is
118.3(2)8. The angular distortions similar to those observed for 1b
are also characteristic of 10: the O(1)—CAr—CAr angles are
113.1(2) and 126.1(2)8. The torsion angle C(8)—O(1)—C(7)—C(6)
(ꢀ0.18) is nearly ideal for the conjugation of the oxygen LEP with
the benzene ring.
˚
C(6). . .C(8) distance is rather short, 2.80 A compared to the
˚
double van der Waals radius ꢂ3.6 A. This short contact could be
avoided by increasing the corresponding torsion angles in the
flexible crown ether.
The nitrogen atom in 1b has a pyramidally distorted
configuration of bonds. The bond angles vary within
112.4(1)–121.5(1)8, the sum of these bond angles being equal
˚
to 351.4(1)8. The N(1)—C(2) bond length is equal to 1.389(2) Aand
However, the geometry about the nitrogen atom in 10 differs
from that in 1b. The nitrogen atom in 10 is involved in efficient
conjugation with the benzene ring. The N(1)—C(2) bond length
˚
[1.369(3) A] is significantly shorter than the corresponding value
˚
in 1b [1.389(2) A] and the torsion angle C(1)—N(1)—C(2)—C(3)
the C(1)—N(1)—C(2)—C(7) torsion angle is equal to 45.08. This
value is a consequence of steric hindrance between the
methylene substituent at the nitrogen atom and the ortho-AlkO
substituent in the benzene ring. The methyl substituent lies
˚
almost in the benzene ring plane, the contact C(3). . .C(15) (2.81 A)
(ꢀ11.48) is suitable for conjugation. The involvement of the LEP of
nitrogen in the conjugation should suppress its interaction with a
metal cation upon complex formation. It should be noted that the
N(1)—CAr—CAr angles [117.2(2) and 123.9(2)8] show a distortion
similar to that observed for the O(1)—CAr—CAr angles in 10
and 1b.
In 10, the hydrogen atom of the NH group points to the centre
of the macrocycle and forms a hydrogen bond with at least one
oxygen atom of the crown ether; the H(1N). . .O(1) distance
being significantly shorter than the double van der Waals
radius. This geometry about the nitrogen atom in 1b is
identical to that found[14] in smaller-size 1a and, apparently,
indicates some conformational rigidity of the crown-ether
fragment in the vicinity of the nitrogen atom and the
benzene ring. This geometry does not provide optimal
conditions for involving the nitrogen LEP into the efficient
conjugation with the benzene ring p-system. However, with
this geometry the nitrogen LEP is oriented toward the metal
˚
(2.16 A) and the N(1)—H(1N). . .O(1) angle (110.78) correspond to
cation approaching the macrocycle. Figure
4
shows the
a weak interaction. Similar structural features were observed[14]
for the N-demethylated benzoazacrown compound 6c. This
hydrogen bond restricting the flexibility of the crown ether,
together with the aforementioned nitrogen atom–benzene ring
conjugation should reduce the chelating properties of this
orientation of LEPs of all heteroatoms of the macrocycle 1b. It
can be seen that the LEPs of most of heteroatoms are oriented
toward the centre of the macrocycle, favourably for co-operative
chelating effect. The O(4) oxygen atom might change its
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Copyright ß 2009 John Wiley & Sons, Ltd.
J. Phys. Org. Chem. 2009, 22 823–833

SYNTHESIS AND COMPLEXATION OF N-METHYLBENZOAZACROWN
Figure 5. Structure of 10 ꢁ CH2Cl2
Figure 7. Structure of 9b
macroheterocycle. Indeed, we observed a pronounced decrease
in the stability constants for the complexes of compounds 6 with
metal cations as compared with those for compounds 1 (Table 2).
For comparison, we also performed an X-ray structural study of
N-(4-formylphenyl)aza-15(18)-crown-5(6) ethers 9a and 9b. Their
molecular structures are shown in Figs 6 and 7. Two crystal-
lographically independent molecules were found in structure 9a.
This fact demonstrates once again a high flexibility of the crown
ethers. The formyl substituent is disordered over two positions in
both molecules of 9a. Tables 3S and 4S (SM) list selected
geometric parameters in 9a and 9b.
The molecules of both compounds 9a,b have a geometry
about the nitrogen atom similar to that found in compound 10
and in the phenylaza-15-crown-5-ether chromophoric com-
pounds studied earlier.[19,20] The nitrogen atom has a nearly
planar geometry; the sums of bond angles in two independent
molecules 9a are equal to 359.3(2) and 360.0(2)8 and that in
molecule 9b is 359.9(1)8. These planes are virtually coplanar to
the benzene rings; the corresponding dihedral angles are 5.4 and
˚
than that in 1b [1.389(2) A]. Thus, the LEP of the nitrogen atom in
9a,b is involved in the conjugation with the benzene ring
resulting in pronounced para-quinoid pattern of its bond length
distribution [Tables 3S and 4S (SM)]. Evidently, a relatively low
stability of the complexes formed by 9a,b and all of the cations
studied (Table 2) is a consequence of this conjugation. Most of
oxygen LEPs are directed to different sides of the macrocycles of
9a and 9b, which is unfavourable for co-operative chelating
effect.
In most of structures investigated here, the crown-ether
fragment is non-symmetrical. However, in solution, it can adopt
different conformations due to its flexibility, including symmetri-
cal crown-like one favourable for the coordination with a metal
cation. This is actually demonstrated by X-ray structural
investigations of two crystalline Ba(ClO4)2 complexes with
N-methylbenzoazacrown ethers 1b and 1c.
˚
2.28 in 9a and 1.08 in 9b. The N—CAr bond length is 1.366(2) A in
˚
both molecules of 9a and 1.377(2) A in 9b, which is comparable
A fragment of the structure of 1b ꢁ Ba(ClO4)2 is shown in Fig. 8
˚
with the corresponding value in 10 [1.369(3) A] and is shorter
and selected geometric parameters are given in Table 5S (SM).
The compound represents
a centrosymmetrically doubled
two-dimensional coordination polymer running along the a-
and c-translations. The independent cell of the polymer includes
two formula units, with ten-fold coordinated Ba2þ ions. Both
barium cations are bound to four oxygen and one nitrogen atoms
of the crown ether and two oxygen atoms of the bidentate
perchlorate anions [Cl(2)O4 and Cl(3)O4]. The other two
perchlorate anions [Cl(1)O4 and Cl(4)O4] perform a bidentate
bridging function to bind a pair of centrosymmetrically related
formula units each (through two different symmetry centres). The
coordination sphere of Ba(1) is supplemented to ten by the
formyl oxygen O(50) atom belonging to the second formula unit
[coordinated to Ba(2)] in the independent cell of the polymer,
whereas the coordination of Ba(2) is supplemented by the formyl
oxygen O(5A). This atom is related to the O(5) atom of the first
formula unit [coordinated to Ba(1)] by the a-translation.
The geometry of the crown-ether coordination to the Ba2þ ions
is nearly identical [Fig. 1S (SM)]. The barium cations are situated
above the mean-square planes through the corresponding
˚
macrocycle heteroatoms, at a distance of ꢂ1.74 A. It is obvious
that such a geometry of the 1:1 complex in solution allows an
expedite approach of the second ligand molecule to form the
2(1b):1(Ba2þ) complex, as it was established in the NMR study (as
shown above). A comparison of 1b ꢁ Ba(ClO4)2 with free 1b
indicates that the macrocycle undergoes an insignificant
Figure 6. Two independent molecules in structure 9a. Formyl groups are
disordered over two positions
J. Phys. Org. Chem. 2009, 22 823–833
Copyright ß 2009 John Wiley & Sons, Ltd.
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S. P. GROMOV ET AL.
Figure 9. Structure of 1c ꢁ Ba(ClO4)2
In 1c ꢁ Ba(ClO4)2, the cation is situated above the mean-square
plane through the macrocycle heteroatoms, at a distance of only
˚
0.63 A [Fig. 2S (SM)], i.e. the cation is much more dipped into the
crown-ether cavity in this complex than in the previous one. In
this case, the corresponding LEPs of all heteroatoms are oriented
towards the metal cation too. Actually, the Ba—O—C angles vary
within 110.2(4)–118.7(5)8 and the Ba—N—C angles, within
104.7(5)–112.5(5)8. The C—N—C angles at the nitrogen atom
range within 108.0(7)–113.7(7)8. The sum of these bond angles
amounts to 330.7(7)8, being indicative of
a pronounced
pyramidal geometry similar to that for the perfect sp3 state of
the nitrogen atom.
Figure 8. Structure of 1b ꢁ Ba(ClO4)2. Here and in Fig. 9, all hydrogen
atoms are omitted for clarity; coordination bonds are depicted as dashed
lines; the additional letter ‘A’ indicates that atoms belong to symmetrically
related units
CONCLUSIONS
Thus, we proposed an improved method for the synthesis of
formyl derivatives of N-methylbenzoazacrown ethers in which
the nitrogen atom is conjugated with the benzene ring. The
method is suitable for preparing individual benzoazacrown
ethers in high yields over fewer steps and with a substantial
shortening of the reaction time at the key stage, i.e.
intramolecular cyclization of the podand halogen derivative.
The high efficiency of complexation of the N-methyl
derivatives of benzoazacrown ethers with metal and ammonium
cations, caused by the pyramidal geometry of the tertiary
nitrogen in the macrocycle and by the pre-organization of the
macrocycle conformation, is demonstrated. The stability of the
resulting complexes of N-methyl derivatives of benzoazacrown
ethers is comparable with or even higher than the stability of
complexes of benzocrown ethers and is much higher than the
stability of complexes formed by phenylazacrown ethers with the
same macrocycle size. This feature and the arrangement of
the nitrogen atom in the para-position of the formyl group in the
benzene ring imply that benzoazacrown compounds having this
structure and their derivatives formed upon modification of the
formyl group may have promising characteristics as ligands for
conformational change upon coordination to the metal cation.
The Ba—O—C angles vary within 106.8(17)–122.3(17)8 and the
Ba—N—C angles range within 103.5(16)–115(2)8. The C—N—C
angles at the nitrogen atoms vary within 107(3)–114(2)8, the
sums of these bond angles being 326(3) and 340(2)8 for the
independent complexes. These data show that the correspond-
ing LEPs of all crown-ether heteroatoms are oriented towards the
Ba2þ ions in the complexes and the sp3 hybridization state of the
nitrogen atoms becomes more pronounced as compared with
free 1b, indicating weakening of the conjugation of the nitrogen
atom LEP with the benzene ring.
Compound 1c ꢁ Ba(ClO4)2 represents a binuclear centrosym-
metric complex with a ten-fold coordination of Ba2þ ions. Two
barium cations are linked via a couple of tridentate chelating
bridging perchlorate anions (Fig. 9). Each of the cations is
coordinated by one more monodentate perchlorate anion and all
heteroatoms of the crown ether. The formyl oxygen does not
participate here in the coordination with the Ba2þ ion. Selected
geometric parameters are given in Table 6S (SM).
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SYNTHESIS AND COMPLEXATION OF N-METHYLBENZOAZACROWN
Group I, II metal cations and ammonium ions and allow one to
predict their use in effective optical molecular sensors.
through a thin Al2O3 layer using benzene and then EtOAc as the
eluents. The yield of 1c was 9 mg (58%).
10-Methyl-2,3,5,6,9,10-hexahydro-8H-1,4,7,10-benzotriox-
azacyclododecine-13-carbaldehyde (1a). Mp 71–72 8C (hex-
ane), mp 71–72 8C.[14] 1H NMR (DMSO-d6, 30 8C) d: 2.85 (s, 3H,
MeN), 3.48 (t, J ¼ 7.3, 2H, CH2N), 3.59 (m, 2H, CH2O), 3.67 (m, 2H,
CH2O), 3.82 (t, J ¼ 7.3, 2H, CH2CH2N), 3.84 (m, 2H, CH2CH2OAr),
4.15 (m, 2H, CH2OAr), 6.89 (d, J ¼ 8.3, 1H, H(11)), 7.29 (d, J ¼ 1.8,
1H, H(14)), 7.42 (dd, J ¼ 8.3, J ¼ 1.8, 1H, H(12)), 9.72 (s, 1H, CH ¼ O).
13-Methyl-2,3,5,6,8,9,12,13-octahydro-11H-1,4,7,10,13-
benzotetraoxazacyclopentadecine-16-carbaldehyde (1b). Mp
49–51 8C (hexane), mp 50–51 8C.[14] 1H NMR (DMSO-d6, 30 8C) d:
2.87 (s, 3H, MeN), 3.30 (t, J ¼ 7.5, 2H, CH2N), 3.57 (s, 4H, 2CH2O),
3.60 (m, 4H, 2CH2O), 3.82 (m, 2H, CH2CH2OAr), 3.86 (t, J ¼ 7.5, 2H,
CH2CH2N), 4.14 (m, 2H, CH2OAr), 6.92 (d, J ¼ 8.3, 1H, H(14)), 7.29 (d,
J ¼ 1.5, 1H, H(17)), 7.42 (dd, J ¼ 8.3, J ¼ 1.5, 1H, H(15)), 9.73 (s, 1H,
CH ¼ O).
EXPERIMENTAL
General information
40-Formylbenzo-12(15,18)-crown-4(5,6) ethers (2a–c)[21,22] and
N-(4-formylphenyl)aza-15(18)-crown-5(6) ethers (9a,b)[23] were
obtained by known methods. CD3CN (water < 0.05%), NaH (60%
in paraffin), THF (water < 0.005%) were used as received (Merck,
Aldrich, or Fluka). NaClO4, KClO4, Ca(ClO4)2 and Ba(ClO4)2 (Aldrich)
were dried in vacuo at 200 8C, NH4ClO4 and EtNH3ClO4 were dried
at 70 8C.
The melting points measured with a MEL-Temp II apparatus in
a capillary are uncorrected. The 1H NMR spectra were recorded on
a Bruker DRX500 (500.13 MHz) instrument in DMSO-d6 and
CD3CN solutions using the solvent as an internal reference (2.50
and 1.96 ppm, respectively). The course of the reactions was
monitored by TLC on DC-Alufolien Kieselgel 60 F254 plates
(Merck). Column chromatography was performed with silica gel
(Kieselgel 60, 0.063–0.100 mm, Merck) and aluminium oxide
(Aluminiumoxid 90, aktiv neutral, 0.063–0.200 mm, Merck).
Elemental analyses were performed at the microanalytical
laboratory of the A. N. Nesmeyanov Institute of Organoelement
Compounds in Moscow, Russia.
16-Methyl-2,3,5,6,8,9,11,12,15,16-decahydro-14H-
1,4,7,10,13,16-benzopentaoxazacyclooctadecine-19-carbal-
dehyde (1c). Yellowish oil.[14] 1H NMR (DMSO-d6, 30 8C) d: 2.95 (s,
3H, MeN), 3.50 (t, J ¼ 5.9, 2H, CH2N), 3.52 (m, 4H, 2CH2O), 3.54 (s,
4H, 2CH2O), 3.60 (s, 4H, 2CH2O), 3.72 (t, J ¼ 5.9, 2H, CH2CH2N), 3.80
(m, 2H, CH2CH2OAr), 4.14 (m, 2H, CH2OAr), 6.89 (d, J ¼ 8.2, 1H,
H(17)), 7.29 (d, J ¼ 1.4, 1H, H(20)), 7.42 (dd, J ¼ 8.2, J ¼ 1.4, 1H,
H(18)), 9.73 (s, 1H, CH ¼ O).
Synthesis of complexes of crown ethers 1b,c with Ba(ClO4)2
(general procedure). A solution of 1b,c (30 mmol) and Ba(ClO4)2
(10 mg, 30 mmol) in acetonitrile (3 ml) was slowly saturated with
benzene by vapour diffusion methods (for 2–3 weeks). The single
crystals formed were collected by decantation and dried in air at
room temperature. The crystals were characterized by elemental
analysis and used for X-ray structural study.
Preparation
Synthesis of benzoazacrown ethers 1a–c (general procedures).
Method A
Complex 1b ꢁ Ba(ClO4)2. Obtained as colourless blocks in 89%
yield; mp > 330 8C (decomp.). Anal. calcld for C16H23BaCl2NO13: C,
29.77; H, 3.59; N, 2.17; found: C, 29.84; H, 3.54; N, 2.19%.
Complex 1c ꢁ Ba(ClO4)2. Obtained as colourless blocks in 65%
yield; mp 302–305 8C (decomp.). Anal. calcld for C18H27BaCl2NO14:
C, 31.35; H, 3.95; N, 2.03; found: C, 31.26; H, 3.84; N, 2.04%.
A mixture of iodide 5a–c (0.1 mmol), anhydrous THF (7 ml) and
40 mg (1 mmol) of 60% NaH in paraffin was refluxed with stirring
for 30 min. After cooling, the reaction mixture was diluted with
water and extracted with benzene. The extracts were washed
with water and concentrated in vacuo, and the residue was
purified by column chromatography on SiO2, using successively a
1: 1 benzene–EtOAc mixture and EtOAc as the eluents to give
1a–c as light yellow oils, from which 1a and 1b crystallized on
standing. The yields of 1a–c are presented in Table 1.
1H NMR titration
The titration experiments were performed in CD3CN solutions at
30 ꢄ 1 8C. A solution of crown ether (L) (0.5 ml, CL ¼ 5 ꢅ 10ꢀ3 M)
and NaClO4, Ca(ClO4)2, Ba(ClO4)2, or EtNH3ClO4 (CM ¼ 0.03 M)
were added in portions to a solution of L in CD3CN (0.5 ml,
CL ¼ 5 ꢅ 10ꢀ3 M). In the case of NH4ClO4 and KClO4,
CL ¼ 2 ꢅ 10ꢀ3 M and CM ¼ 0.012 M were used for titration due
to the low solubility of the salts in CD3CN. In the case of
competitive titration, a solution (0.5 ml) containing a mixture of L,
metal perchlorate and the competing ligand (L’) (CL ¼ 5 ꢅ 10ꢀ3 M,
CM ¼ 6 ꢅ 10ꢀ3 M, CL’ ¼ 0.2 M) was added in portions to a solution
of a mixture of L and metal perchlorate in CD3CN (0.5 ml,
CL ¼ 5 ꢅ 10ꢀ3 M, CM ¼ 6 ꢅ 10ꢀ3 M). The proton chemical shifts
were measured as a function of the M/L or L’/L ratio and the
complex formation constants were then calculated using the
HYPNMR program.[17]
Method B
A mixture of iodide 5a–c (0.1 mmol), anhydrous THF (7 ml) and
60% NaH (40 mg, 1 mmol) in paraffin was stirred at room
temperature until the initial iodide disappeared (TLC monitoring).
The mixture was worked-up as in Method A. The reaction time and
the yields of 1a–c are presented in Table 1.
Method C
A mixture of chloride 4b,c (0.1 mmol), anhydrous THF (7 ml) and
60% NaH in paraffin (40 mg, 1 mmol) was refluxed with stirring
until the initial chloride disappeared (TLC monitoring). The
workup was similar to that in Method A. The reaction time and the
yields of 1b,c are presented in Table 1.
Methylation of benzoazacrown ether 6c. A mixture of
azacrown ether 6c (15 mg, 44 mmol), 60% NaH (35 mg, 0.88 mmol)
in paraffin, MeI (27 ml, 0.44 mmol) and anhydrous THF (4 ml) was
refluxed for 30 min. The reaction mixture was diluted with water
and extracted with benzene. The extracts were washed with
water and concentrated in vacuo and the residue was passed
X-ray experiments
Crystals of compounds 1b, 9a,b and 10 ꢁ CH2Cl2 were obtained by
slow evaporation of the CH2Cl2–hexane solutions. Crystals of
J. Phys. Org. Chem. 2009, 22 823–833
Copyright ß 2009 John Wiley & Sons, Ltd.
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S. P. GROMOV ET AL.
complexes 1b and 1c with Ba(ClO4)2 were grown as described
above. Single crystals of all compounds were coated with
perfluorinated oil and mounted on a Bruker SMART–CCD
diffractometer (graphite monochromatized Mo-Ka radiation,
space group P 1 (no. 2), Z ¼ 4, m(Mo-Ka) ¼ 2.066 mmꢀ1, 8473
reflections measured, 5216 unique (Rint ¼ 0.0335) which
were used in all calculations. The final R1 and wR2 were
0.1521 and 0.3558 for 4807 reflections with I > 2s(I), 0.1562
and 0.3573 for all data. SADABS absorption correction was
applied.
˚
l ¼ 0.71073 A, v scan mode) under a stream of cold nitrogen
(T ¼ 120.0(2) K).
All structures were solved by direct methods and refined by
full-matrix least-squires on F2 in anisotropic approximation for
non-hydrogen atoms. A disorder of the formyl groups of two
independent molecules 9a over two positions with a ratio of site
occupation factors equal to 0.77:0.23 and 0.95:0.05 was observed.
It was found that the substituent in the benzoazacrown ether
10 ꢁ CH2Cl2 is carboxyl rather than formyl. This observation was
supported by bond lengths and the presence of a hydrogen atom
at one of carboxyl oxygens.
Crystal data for 1c ꢁ Ba(ClO4)2: C18H27BaCl2NO14, M ¼ 689.65,
˚
monoclinic, a ¼ 8.9885(5), b ¼ 26.7470(14), c ¼ 10.7487(6) A,
3
˚
b ¼ 107.870(2)8, V ¼ 2459.5(2) A , space group P21/n (no. 14),
Z ¼ 4, m(Mo-Ka) ¼ 1.904 mmꢀ1, 26650 reflections measured, 5898
unique (Rint ¼ 0.0315) which were used in all calculations. The
final R1 and wR2 were 0.0655 and 0.1658 for 5408 reflections with
I > 2s(I), 0.0703 and 0.1675 for all data. SADABS absorption
correction was applied.
The crystallographic parameters, data collection and structure
solution details, and the refinement parameters for 1b, 9a, 9b,
10 ꢁ CH2Cl2, 1b ꢁ Ba(ClO4)2, and 1c ꢁ Ba(ClO4)2 are given also in
Tables 7S-9S (SM).
All the calculations were performed using SHELXTL-Plus
software.[24] Crystallographic data (excluding structure factors)
for the structures have been deposited with the Cambridge
Crystallographic Data Centre as supplementary publication nos
CCDC 694336 (1b), 694338 (9a), 694339 (9b), 694340
(10 ꢁ CH2Cl2), 694335 (1b ꢁ Ba(ClO4)2), 694337 (1c ꢁ Ba(ClO4)2). A
copy of the data can be obtained free of charge on application to
CCDC, 12 Union Road, Cambridge CB21EZ, UK (fax:
(þ44)1223-336-033; E-mail: deposit@ccdc.cam.ac.uk).
The positions of hydrogen atoms were calculated geome-
trically and then refined isotropically [for 1b, 9a,b and 10 ꢁ CH2Cl2
(except for the hydrogen atom of the carboxyl group of
10 ꢁ CH2Cl2 and the hydrogen atoms of the disordered formyl
groups in two independent molecules of 9a which were refined
using a riding model)] or using a riding model [for 1b ꢁ Ba(ClO4)2
and 1c ꢁ Ba(ClO4)2].
A low quality of single crystals 1b ꢁ Ba(ClO4)2 and 1c ꢁ Ba(ClO4)2
did not allow us to achieve accurate structures. We obtained high
values of R1 and wR2 and residuals. However, all peaks of residual
electron density are located in the vicinity of heavy atoms. In spite
of low accuracy, we believe that the obtained structural motifs are
correct enough to discuss the conformation features, as well as
the change in the conformation of free 1b upon its coordination
to the metal cation.
Acknowledgements
Crystal data for 1b: C16H23NO5, M ¼ 309.35, triclinic,
˚
The authors thank Olga V. Tikhonova for preparation of the
requited amounts of 1b and 1c. Financial support from the
Russian Foundation for Basic Research (Projects No.
06-03-32456 and 06-03-33162), the Ministry of Education and
Science of the Russian Federation, the Russian Academy of
Sciences, the Royal Society of Chemistry (L.G.K. and A.I.V.), and
the EPSRC for a Senior Research Fellowship (J.A.K.H.) is gratefully
acknowledged.
a ¼ 8.1791(5), b ¼ 10.0518(6), c ¼ 10.6693(6) A, a ¼ 103.293(3),
3
˚
b ¼ 100.998(3), g ¼ 104.598(3)8, V ¼ 796.78(8) A , space group
P 1 (no. 2), Z ¼ 2, m(Mo-Ka) ¼ 0.095 mmꢀ1, 8179 reflections
measured, 4158 unique (Rint ¼ 0.0398) which were used
in all calculations. The final R1 and wR2 were 0.0436 and
0.1066 for 3128 reflections with I > 2s(I), 0.0640 and 0.1150 for all
data.
Crystal data for 9a: C17H25NO5, M ¼ 323.38, monoclinic,
˚
a ¼ 24.2125(7), b ¼ 15.3431(4), c ¼ 8.8104(3) A, b ¼ 92.6370(10)8,
3
˚
V ¼ 3269.55(17) A , space group P21/c (no. 14), Z ¼ 8,
m(Mo-Ka) ¼ 0.096 mmꢀ1
, 27753 reflections measured, 8656
REFERENCES
unique (Rint ¼ 0.0570) which were used in all calculations. The
final R1 and wR2 were 0.0540 and 0.1196 for 5463 reflections with
I > 2s(I), 0.0972 and 0.1312 for all data.
[1] T. Yordanov, D. M. Roundhill, Coord. Chem. Rev. 1998, 170, 93–124.
DOI: 10.1016/S0010-8545(97)00074-X
Crystal data for 9b: C19H29NO6, M ¼ 367.43, monoclinic,
[2] K. Gloe, H. Graubaum, M. Wust, T. Rambusch, W. Seichter, Coord. Chem.
Rev. 2001, 222, 103–126. DOI: 10.1016/S0010-8545(01)00397-6
[3] P. Buhlmann, E. Pretsch, E. Bakker, Chem. Rev. 1998, 98, 1593–1687.
DOI: 10.1021/cr970113þ
˚
a ¼ 21.6266(6), b ¼ 10.3060(3), c ¼ 8.4947(2) A, b ¼ 98.747(2)8,
3
˚
V ¼ 1871.31(9) A , space group P21/c (no. 14), Z ¼ 4,
m(Mo-Ka) ¼ 0.096 mmꢀ1
, 12397 reflections measured, 4813
[4] P. de Silva, H. Q. N. Gunaratne, T. Gunnlaugsson, A. J. M. Huxley, C. P.
McCoy, J. T. Rademacher, T. E. Rice, Chem. Rev. 1997, 97, 1515–1566.
DOI: 10.1021/cr960386p
unique (Rint ¼ 0.0439) which were used in all calculations. The
final R1 and wR2 were 0.0564 and 0.1044 for 3280 reflections with
I > 2s(I), 0.0939 and 0.1133 for all data.
[5] M. V. Alfimov, S. P. Gromov, in Applied Fluorescence in Chemistry,
Biology, and Medicine, (Eds: W. Rettig, B. Strehmel, S. Schrader, H.
Seifert), Springer-Verlag, Berlin, 1999; 161–178.
[6] B. Valeur, I. Leray, Coord. Chem. Rev. 2000, 205, 3–40. DOI: 10.1016/
S0010-8545(00)00246-0
[7] S. Shinkai, in Comprehensive Supramolecular Chemistry, Vol. 1(Ed.: G.
W. Gokel), Pergamon, Oxford, 1996; 671–700.
[8] S. P. Gromov, M. V. Alfimov, Russ. Chem. Bull. 1997, 46, 611–636.
DOI:10.1007/BF02495186
[9] A. Mishra, R. K. Behera, P. K. Behera, B. K. Mishra, G. B. Behera, Chem.
Rev. 2000, 100, 1973–2011. DOI:10.1021/cr990402t
[10] E. Krakowiak, J. S. Bradshaw, D. J. Zamecka-Krakowiak, Chem. Rev.
1989, 89, 929–972. DOI: 10.1021/cr00094a008
Crystal data for 10 ꢁ CH2Cl2: C16H23Cl2NO6, M ¼ 396.25, triclinic,
˚
˚
a ¼ 8.3696(7), b ¼ 11.1611(10), c ¼ 11.7965(10) A, a ¼ 106.926(2),
3
b ¼ 109.505(2), g ¼ 104.921(2)8, V ¼ 913.63(14) A , space group
P 1 (no. 2), Z ¼ 2, m(Mo-Ka) ¼ 1.440 mmꢀ1, 5104 reflections
measured, 4184 unique (Rint ¼ 0.0170) which were used in all
calculations. The final R1 and wR2 were 0.0543 and 0.1480 for 3151
reflections with I > 2s(I), 0.0750 and 0.1575 for all data.
Crystal data for 1b ꢁ Ba(ClO4)2: C16H23BaCl2NO13, M ¼ 645.59,
˚
triclinic,
a ¼ 10.7252(19),
b ¼ 12.955(2),
c ¼ 16.522(3) A,
3
˚
a ¼ 100.747(3), b ¼ 91.160(4), g ¼ 90.423(4)8, V ¼ 2254.8(7) A ,
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SYNTHESIS AND COMPLEXATION OF N-METHYLBENZOAZACROWN
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J. Phys. Org. Chem. 2009, 22 823–833
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