Synthesis and properties of potassium salts of per-O-carboxymethyl-calix[4] pyrogallols and their complexes with Cu2+, Fe3+, and La3+

Article abstract of DOI:10.1007/s11172-009-0012-8

Synthesis of water-soluble potassium salts of carboxymethyl derivatives of calix[4]pyrogallols and dodeca(carboxylatomethyl)tetramethylcalix[4]pyrogallol (L) complexes with transition metal ions (Cu²⁺, Fe³⁺, La³⁺) is descr

Full text of DOI:10.1007/s11172-009-0012-8

80
Russian Chemical Bulletin, International Edition, Vol. 58, No. 1, pp. 80—88, January, 2009
Synthesis and properties of potassium salts of perꢀOꢀcarboxymethylꢀ
2
+
3+
3+
calix[4]pyrogallols and their complexes with Cu , Fe , and La
a
a
a
b
S. N. Podyachev, S. N. Sudakova, V. V. Syakaev, N. E. Burmakina,
a
a
a
a
R. R. Shagidullin, V. I. Morozov, L. V. Avvakumova, and A. I. Konovalov
aA. E. Arbuzov Institute of Organic and Physical Chemistry,
Kazan Research Center of the Russian Academy of Sciences,
8
ul. Akad. Arbuzova, 420088 Kazan, Russian Federation.
Fax: +7 (843) 273 2253. Eꢀmail: spodyachev@iopc.knc.ru
b
Kazan State Technological University,
6
8 ul. K. Marksa, 420015 Kazan, Russian Federation
Synthesis of waterꢀsoluble potassium salts of carboxymethyl derivatives of calix[4]pyrogallols
and dodeca(carboxylatomethyl)tetramethylcalix[4]pyrogallol (L) complexes with transition
2
+
3+
3+
metal ions (Cu , Fe , La ) is described. Their structures in the solid state and in solution
were characterized by NMR spectroscopy, ESR, and IR spectroscopy. Calix[4]pyrogallol
dodecacarboxylates exist in the rcccꢀconfiguration. Calix[4]pyrogallol with methyl substituents
at the lower rim in a wide range concentrations exists in water predominantly in the dimeric
form. The obtained polynuclear transition metal complexes possess less symmetric structure
than potassium salt of calix[4]pyrogallol (K12L). All studied complexes contain water molꢀ
ecules bound by rather strong hydrogen bonds. At room temperature the Fe L complex is
4
3
+
characterized by the environment of the Fe ions close to octahedral. The absence of signals
in the ESR spectrum of the Cu L complex indicates the strong antiferromagnetic interaction
6
2
+
2+
Cu —Cu
.
Key words: calix[4]arenes, calix[4]pyrogallols, carboxylic acids, potassium salts, copper
complexes, iron complexes, lanthanum complexes, aggregation, complexation.
decades,13,14 created exclusive possibilities for the modifiꢀ
cation of properties of the known ligating groups. Immoꢀ
bilization of several such groups on the calixarene frameꢀ
work allows one to obtain compounds of the new type,
which can be named supermolecular ligands. They are
characterized by a combination of the properties of cheꢀ
lates, podands, and macrocyclic polydentate compounds.
An important feature of these ligands is the manifestation
of the cooperative effect of binding groups due to their
preꢀorganization in a molecule.
Carboxylic acids and their complexes are of interest as
objects of wideꢀscope basic research (for example, many
publications (see, e.g., Refs 1 and 2) are devoted to studyꢀ
ing the properties of one of the simplest carboxylates,
2
+
namely, Cu acetate) and also as compounds promising
for practical use.3 Particularly, their use in coordinaꢀ
tion chemistry is due to the fact that the carboxylate
anions are efficient donor groups for binding alkaline and
—6
7
transition metal ions. Several coordination sites are
necessary to provide high efficiency and especially selecꢀ
tivity of binding. Therefore, structurally organized polyꢀ
carboxylic acids serve as a basis for the creation of
complexones for a series of metal ions. In addition, they
can form various polynuclear complexes including highꢀ
The immobilization of four acetylhydrazide groups
on the calix[4]arene platform produces the efficient and
1
5,16
selective extractant of transition metal ions.
It should
be mentioned that these properties were not found for the
monomeric analog. The functionalization of calix[4]phenol
6
spin transition metal atoms. The presence of unpaired
1
7—19
electrons results in the appearance of unique magnetic
and electrophysical properties, which can be used for the
by carboxy groups
makes it possible to obtain a more
selective ligand for binding lanthanide ions than comꢀ
plexones based on polycarboxylic acids. We have previꢀ
6
,8—12
creation of molecular devices.
However, despite
2
0
achieved success, the synthesis of sterically organized
polycarboxylic acids remains urgent.
The development of organic chemistry and especially
chemistry of calix[n]arenes, which became traditional
objects of supramolecular science during the recent
ously found that the introduction of carboxy fragments
into the calix[4]resorcinol matrix provided the formation
of the efficient ionophore with the pHꢀcontrolled selecꢀ
tivity. In the case of calix[4]pyrogallols, the efficiency of
complexation with lanthanide and alkaline metal ions was
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 80—88, January, 2009.
066ꢀ5285/09/5801ꢀ080 © 2009 Springer Science+Business Media, Inc.
1

Calix[4]pyrogallol polycarboxylic complexes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
81
Scheme 1
R1 = Me (1, 5), C H (2, 6);
9
19
M = Cu, n = 2 (9); M = Fe, n = 3 (10); M = La, n = 3 (11)
enhanced compared to their monomeric blocks.21 It was
shown that the efficiency and selectivity of binding are
substantially determined by structural features of the synꢀ
thesized compounds and not only the number (effective
concentration) of binding groups in the molecules.
used. Resorcinol, pyrogallol, methyl and ethyl bromoacetates,
CuCl , FeCl •6H O, CDCl (99.8%), D O (99%), and DMSOꢀd
6
2
3
2
3
2
(
99.5%) were purchased from Merck, Acros, or Aldrich and
used without additional purification; MeCN and Me CO
2
(
reagent grade) were dried by distillation over P O ; EtOH (96%)
2 5
was used as purchased.
One of the most efficient methods for preparation of
transition metal complexes is the exchange reaction of
alkaline metal ions in their salts for the corresponding
ions. For this purpose, we synthesized potassium salts of
calix[4]pyrogallols functionalized at all hydroxy groups
by carboxymethyl substituents. Their structural and aggregaꢀ
tion properties were studied and compared with the
monomeric analog: potassium salt of 1,2,3ꢀtris(carboxyꢀ
The NMR spectra were detected on an AVANCE 600
spectrometer (Bruker) equipped with a gradient block (field
–
1
gradient to 50 G cm ); working frequency of the spectrometer
1
13
being 600.13 ( H) and 125.86 MHz ( С). A 5ꢀmm inverse sensor
with the gradient coil along the Z axis was used. The spectra
were recorded at 303 K. The chemical shifts are presented
relatively to Me Si as the internal standard for samples in CDCl
4
3
and residual signals of Н О for samples in D O (δ(Н О) 4.72).
2
2
2
In experiments on measuring the selfꢀdiffusion coefficient
2
+
3+
3+
methyl)benzene. New polynuclear Cu , Fe , and La
(
D ), the correlation coefficient of the relative decrease in the
s
complexes with the 2,8,14,20ꢀtetramethylcalix[4]pyroꢀ
gallol dodecarboxylate derivative were synthesized. The
general route for synthesis of the studied compounds is
shown in Scheme 1.
NMR signal (lnI/I ) with the pulse gradient of the magnetic field
0
2
2
2
b = γ δ g (∆ – δ/3),
(
γ is the gyromagnetic ratio of protons, g is the amplitude of the
magnetic field pulse gradient, ∆ is the interval between the
gradient pulses, and δ is the duration of the gradient pulses)
exceeded 0.999 in all presented data. The amplitude of the
magnetic gradient was changed linearly from 0 to 32 G cm–1 for
16 increments. The duration of the gradient pulses was δ = 2.8 ms,
and the interval between the gradient pulses was ∆ = 50 ms. The
Experimental
The starting unsubstituted calix[4]pyrogallols 1 and 2 were
2
2,23
synthesized by known procedures.
Metal chlorides, nitrates,
and hydroxides (analytical purity grade) and distilled water were

82
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Podyachev et al.
arithmetic mean D values are presented for all resolved signals
added to crude calix[4]pyrogallol ester 3 (1.47 g, 1 mmol) in
boiling EtOH (15 mL). The reaction mixture was stirred for 12 h
under reflux. The precipitate that formed was filtered off, washed
with hot EtOH, and dried in vacuo (0.1 Torr, 2 h) at 110—120 °С.
Salt 5 was obtained as a white powder in a yield of 1.68 g (95%),
m.p. 320 °C (with decomp.). Found (%): С, 36.45; H, 2.57;
K, 25.51. C56H52K12O40 (with allowance for four water molecules).
Calculated (%): C, 36.67; H, 2.86; K, 25.58.
s
in the NMR spectra. The error of D measurement was 5%, and
s
the error of temperature stabilization was 0.1 K. The standard
pulse sequences from the spectrometer library were used for all
NMR experiments.
The theoretical D values were calculated by the HYDRONMR
s
2
4
program. The structures of calixarenes used for the calculation
of D were optimized by the molecular mechanics method using
s
2
5
the Chem3D program. The hydrodynamic radius (R ) was
Dodecapotassium salt of 2,8,14,20ꢀtetranonylꢀ4,5,6,10,11,
12,16,17,18,22,23,24ꢀdodeca(carboxymethoxy)pentacycloꢀ
H
calculated from the selfꢀdiffusion coefficients (D ) by the
s
3
,7 9,13 15,19
Stokes—Einstein equation
[19.3.1.1 .1 .1
]octacosaꢀ1(25),3,5,7(28),9,11,13(27),
1
5,17,19(26),21,23ꢀdodecaene (6), tetrahydrate (K12L´•4H O).
2
D = kT/6πηR ,
Compound 6 was synthesized similarly to compound 5 from
calix[4]pyrogallol 4 (2.1 g, 1 mmol) (solution in 20 mL of
EtOH) and KOH (1.34 g, 24 mmol) (solution in 15 mL
of EtOH). Salt 6 as a white powder was obtained in a yield of
1.5 g (68%), m.p. 305 °C (with decomp.). Found (%): C, 46.34;
H, 5.38; K, 20.77. C88H116K12O40 (with allowance for four water
molecules). Calculated (%): C, 46.30; H, 5.12; K, 20.55.
1,2,3ꢀTris(methoxycarbonylmethoxy)benzene (7) was synꢀ
thesized similarly to compound 3 from pyrogallol (12.6 g, 0.1 mol),
K CO (55 g, 0.4 mol), and methyl bromoacetate (67 g, 0.4 mol)
s
H
where k is the Boltzmann constant, Т is the absolute temperaꢀ
ture, and η is the solvent viscosity.
The geometry of the model for the dimeric structure with
the K+ ions was optimized by the semiempirical method (АМ1)
26
2
7
included into the HyperChem7.03 program package.
The MALDIꢀTOF mass spectra were measured on a Finnigan
MALDIꢀTOF Dynamo mass spectrometer (1,8,9ꢀtrihydroxyꢀ
anthracene or 4ꢀnitroaniline as the matrix). The IR absorption
spectra were recorded for emulsions in Nujol or in KBr pellets
on a Vectorꢀ22 FTꢀIR spectrometer (Bruker) with a resolution
of 4 cm–1 and 16 scan accumulation. In the both cases, the
spectra were nearly the same, which excludes the possibility for
substances to react with the medium. The ESR spectra were
detected on a Radiopan SE/Xꢀ2544 spectrometer in the range
from 293 to 133 K.
2
3
in Me CO (200 mL). The reaction mixture was stirred for 24 h
2
with reflux under argon. Ester 7 as a white powder was obtained
in a yield of 19.8 g (60%), m.p. 67 °C. Found (%): C, 52.68; H,
5.23. C H O . Calculated (%): C, 52.63; H, 5.30. MALDIꢀTOF
1
5
18 9
+
+
+
MS, m/z: 343 [M + H] , 366 [M + Na] , 381 [M + K] .
Tripotassium salt of 1,2,3ꢀtris(carboxymethoxy)benzene (8),
hydrate (K L″•H O). Compound 8 was synthesized similarly to
3
2
2
,8,14,20ꢀTetramethylꢀ4,5,6,10,11,12,16,17,18,22,23,24ꢀ
compound 5 from ester 7 (0.77 g, 2 mmol) (solution in 30 mL of
EtOH) and KOH (0.5 g, 9 mmol) (solution in 10 mL of EtOH).
Potassium salt 8 as a white powder was obtained in a yield of
0.65 g (80%), m.p. 330 °C (with decomp.). Found (%): C, 33.67;
H, 2.87; K, 26.97. C12H11K O (with allowance for one water
3
,7 9,13
dodeca(methoxycarbonylmethoxy)pentacyclo[19.3.1.1 .1
.
1
5,19
1
]octacosaꢀ1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23ꢀ
dodecaene (3). Methyl bromoacetate (15.3 g, 0.1 mol) was added
with stirring at ~20 °C to a mixture of calix[4]pyrogallol 1
3
10
(
3.65 g, 6 mmol) and K CO (16.6 g, 0.12 mol) in anhydrous
molecule). Calculated (%): C, 33.32; H, 2.56; K, 27.12.
2
3
MeCN (100 mL). The reaction mixture was stirred for 3 days
with reflux under argon and filtered, and the solvent was distilled
off. The oily residue was dissolved in dichloromethane and
washed with water several times. The organic layer was separated
{2,8,14,20ꢀTetramethylꢀ4,5,6,10,11,12,16,17,18,22,23,24ꢀ
3
,7 9,13 15,19
dodeca(carboxylatomethoxy)pentacyclo[19.3.1.1 .1 .1
]ꢀ
octacosaꢀ1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23ꢀ
dodecaene}hexacopper(II) (9), hexahydrate (Cu L•6H O).
6
2
and dried over MgSO , and the solvent was distilled off. The
A solution of CuCl2 (0.14 g, 1 mmol) in water (5 mL) was
poured with vigorous stirring to a solution of potassium salt 5
(0.3 g, 0.17 mmol) in water (5 mL). The reaction mixture was
stirred for 1 h at the temperature of the bath 40 °С. The
precipitate that formed was filtered off, washed with water and
EtOH, and dried in vacuo (0.1 Torr, 1 h) at 80 °С. Complex 9
as a light blue powder was obtained in a yield of 0.27 g (90%),
m.p. >300 °C. Found (%): C, 37.73; H, 3.34; Cu, 21.73.
C56H56Cu O (with allowance for six water molecules). Calꢀ
4
solvent residues were removed in vacuo at 100 °C. Ester 3 as a
white powder was obtained in a yield of 6 g (68%), m.p. 139—141 °C.
Found (%): C, 55.44; H, 5.50. C68H80O36. Calculated (%):
+
C, 55.43; H, 5.47. MALDIꢀTOF MS, m/z: 1473 [M + H] ,
+
+
1
497 [M + Na] , 1512 [M + K] .
,8,14,20ꢀTetranonylꢀ4,5,6,10,11,12,16,17,18,22,23,24ꢀ
2
3
,7 9,13
dodeca(ethoxycarbonylmethoxy)pentacyclo[19.3.1.1 .1
.
15,19
1
]octacosaꢀ1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23ꢀ
6
42
dodecaene (4). Compound 4 was synthesized similarly to comꢀ
pound 3 from calix[4]pyrogallol 2 (6.3 g, 6 mmol), K CO (16.6
g, 0.12 mol), and ethyl bromoacetate (16.7 g, 0.1 mol) in MeCN
culated (%): C, 37.74; H, 3.17; Cu, 21.39.
{2,8,14,20ꢀTetramethylꢀ4,5,6,10,11,12,16,17,18,22,23,24ꢀ
dodeca(carboxylatomethoxy)pentacyclo[19.3.1.1 .1 .1
2
3
3
,7 9,13 15,19
]ꢀ
(
100 mL). For spectra studies the product was additionally
octacosaꢀ1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23ꢀ
purified by column chromatography on silica gel using a
petroleum ether—AcOEt (20 vol.%) mixture as the eluent. Ester
dodecaene}tetrairon(III) (10), tetrahydrate (Fe L•4H O). Comꢀ
pound 10 was synthesized analogously to complex 9 from
4
2
4
(7.1 g, 57%) was obtained as a viscous light yellow oil. Found (%):
solutions of salt 5 (0.3 g, 0.17 mmol) and FeCl •6H O (0.19 g,
3
2
C, 63.93; H, 8.37. C112H168O36. Calculated (%): C, 64.35; H,
0.7 mmol) in water (5 mL). Complex 10 as a light beige powder
was obtained in a yield of 0.26 g (96%), decomp.p. >300 °C.
Found (%): C, 42.36; H, 3.11; Fe, 14.56. C56H52Fe O (with
allowance for four water molecules). Calculated (%): C, 42.32;
H, 3.30; Fe, 14.09.
+
+
8
.10. MALDIꢀTOF MS, m/z: 2116 [M + Na] , 2132 [M + K] .
Dodecapotassium salt of 2,8,14,20ꢀtetramethylꢀ4,5,6,10,
1,12,16,17,18,22,23,24ꢀdodeca(carboxymethoxy)pentacycloꢀ
4
40
1
[
19.3.1.13 .1 .1
,7
9,13 15,19
]octacosaꢀ1(25),3,5,7(28),9,11,13(27),
5,17,19(26),21,23ꢀdodecaene (5), tetrahydrate (K12L•4H O).
1
{2,8,14,20ꢀTetramethylꢀ4,5,6,10,11,12,16,17,18,22,23,24ꢀ
2
3
,7 9,13 15,19
A solution of KOH (1.34 g, 24 mmol) in EtOH (15 mL) was
dodeca(carboxylatomethoxy)pentacyclo[19.3.1.1 .1 .1
]ꢀ

Calix[4]pyrogallol polycarboxylic complexes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
83
octacosaꢀ1(25),3,5,7(28),9,11,13(27),15,17,19(26),21,23ꢀ
with calix[4]pyrogallols 1 and 2 and pyrogallol, respecꢀ
tively (see Scheme 1). The hydrolysis of these esters in
excess KOH in an EtOH medium produced waterꢀsoluble
polycarboxylic acids 5, 6, and 8, which required no addiꢀ
tional purification. Mixing of potassium salt of calix[4]pyroꢀ
gallol 5 with equimolar amounts of CuCl , FeCl , and
dodecaene}tetralanthanum(III) (11), hexahydrate (La L•6H O).
4
2
Compound 11 was synthesized analogously to complex 9
from solutions of salt 5 (0.3 g, 0.17 mmol) and La(NO ) •6H O
3
3
2
(0.3 g, 0.7 mmol) in water (5 mL). Complex 11 as a white powder
was obtained in a yield of 0.32 g (96%), decomp.p. >300 °C.
Found (%): C, 34.40; H, 2.97; La, 28.24. C56H56La O (with
2
3
4
42
La(NO ) in water resulted in the precipitation of comꢀ
allowance for six water molecules). Calculated (%): C, 34.38;
3 3
H, 2.88; La, 28.40.
plexes 9—11, which were isolated in high yields.
The compositions and structures of the synthesized
macrocyclic compounds were established by the data
of elemental analysis, MALDIꢀTOF mass spectrometry,
Results and Discussion
1
Calix[4]pyrogallols are convenient matrices for the
introduction of various functional groups. (Areneꢀ1,2,3ꢀ
triyl)tris(oxyacetic acid) esters 3, 4, and 7 were syntheꢀ
sized by the reactions of methyl or ethyl bromoacetate
Н NMR, and 2D and IR spectroscopies.
Spectral and structural features of potassium salts 5, 6,
and 8 according to the IR and NMR spectroscopic data.
The IR spectra of potassium salts 5, 6, and 8 (Fig. 1)
Table 1. NMR spectra of compounds 3, 4, 7 (in CDCl ) and 5, 6, 8 (in D O) at 303 K
3
2
Atoma
C or H
δ (J/Hz)
3
4
5
6
7
8
1H
—
13C
1H
—
13C
1H
—
13C
133.44,
1H
—
13C
1H
—
13C
1H
—
13C
1
2
3
143.27
143.26
138.70
138.33
136.12
1
38.72
b
—
—
147.77
135.42
—
—
148.05
134.02
—
—
147.40 ,
—
—
148.39
144.02
—
151.87
—
151.93
c
1
48.15
133.41,
6.58 109.26 (d, 6.57
107.07 (d,
J = 162)
1
1
1
1
38.27,
43.94,
J = 160)
1
44.37
b
b
b
4
6.35 121.04 (d, 6.22,
121.65
6.22 ,
120.66 ,
121.66
6.24 ,
121.24
6.96 124.17 (d, 7.04
124.55 (d,
J = 163)
1
c
c
c
1
1
J = 156)
7.48
4.61
1.83
1.27
7.29
6.95
J = 163)
(
both br)
4.66
5
6
7
4.72
1.41
—
32.25 (d,
J = 130)
20.85
—
37.26
35.46
22.83,
4.77
1.46
—
31.68 (d,
J = 128)
36.84
36.73
—
—
—
—
—
—
—
—
—
—
—
—
1
1
21.99 (q,
1.77
1
J = 128)
—
1.25
(br)
22.97,
28.40,
29.54,
29.72,
30.23,
30.54,
32.33
2
2
2
2
3
8.33,
9.51,
9.80,
9.91,
0.18,
3
2.10
8
1
—
4.16 ,
.58
—
69.82 ,
70.18
0.88
4.19,
4.54,
14.31
—
3.24
4.24c,e
—
0.77
14.54
—
4.72 ,
4.78
—
66.84 ,
69.92d
—
4.47 ,
4.52e
—
d
e
e
c,d
e
e
d
e
´
69.83 ,
,
71.44, 3.25 (br), 71.77,
71.79,
72.70
67.50 (t,
e
d
d
d
1
4
70.18
,
4.19,
4.21,
4.35
—
72.42
J = 148);
b,d
d
4
.65
4.37
,
71.81 (t,
1
4
.54b,e
—
J = 147)
177.09 ,
177.51
d
d
e
e
2
3
4
´
´
´
—
169.29 ,
69.72e
51.91
—
168.82 ,
176.5,
177.1
—
176.83,
176.41
—
—
169.44 ,
169.93
52.08 ,
52.31e
—
—
—
—
d
d
1
169.22e
60.83
e
d
3.65
—
4.24
1.26
—
—
—
—
3.80 ,
.82
—
—
—
d
3
—
14.22
—
—
a
b
c
Numbering is given in Scheme 1.
For the fragment pointed outside (see text).
For the fragment pointed inside (see text).
For substituents in position a.
d
e
For substituents in position b.

84
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Podyachev et al.
Absorption (%)
rcccꢀisomer does not transform into other isomers even at
high temperatures.3
3,34
5
6
Other, predominantly rcttꢀisomers are usually formed
during the condensation of resorcinols and pyrogallols
2
1,32
with more bulky aromatic aldehydes.
The substitution
of protons of the hydroxy groups in calix[4]resorcinols
and calix[4]pyrogallols affords more conformationally
flexible compounds than the starting calix[4]arenes but
with the retention of the isomer type.3
8
9
1
With allowance for the aforesaid, to confirm the proꢀ
posed rcccꢀconfiguration of calix[4]arenes 1—4, it is
enough to determine the spatial structure of their derivaꢀ
tives 5 and 6. Since the spectra of calix[4]pyrogallols 5
and 6 with methyl and nonyl substituents, in further disꢀ
cussion we will restrict our detailed consideration by the
spectra of only compound 5.
1
1
0
1
ν(H O)
νs(CO2–)
2
The spectrum of compound 5 contains one signal of
the bridging proton H(5) and two signals of aromatic
protons H(4) (δ 7.29 and 6.22). This shape of the specꢀ
trum is characteristic of calix[4]arene in the boat conforꢀ
mation in which two opposite aromatic rings are nearly
parallel to each other along the axial axis and two other
rings are turned out and lie in the planes close to the
equatorial one. The H(4) protons of the aromatic, turned
out rings are between two adjacent aromatic rings and
experience the highꢀfield shift due to their circular curꢀ
rents. This made it possible to assign signals of the protons
for the both pairs of the fragments using the HMBC exꢀ
νas(CO2–)
ν/cm–1
1
000
2000
3000
Fig. 1. IR spectra of potassium salts 5, 6, and 8 and complexes
—11.
9
correspond to the structural formulas ascribed to them,
and they are characterized by the following analytical
2
8,29
absorption bands known from previous studies
:
–
1
–1
–1
~
(
(
1
3390—3250 cm (m, vbr, ν(ОН)); 3100—2800 cm
–
1
–
w, ν(СН)); ~1600 cm (vs, ν (CO )) and ~1420 cm
s, ν (CO )); ~1310 cm (s, ν(=С—О) arom.); ~1100—
s 2
050 cm (m, ν(=С—С), ν(С—О)); ~700 cm–1 (m,
as 2
–
–1
–
1
1
13
periments in which Н— С correlations are manifested
through two and three bonds (see Table 1).
–
δ(СО )). A series lowꢀintensity peaks and inflections are
2
observed at 1600—1400, 1300—1100, 1050—800, and
The spectra of triester 7 and tripotassium salt 8 exhibit
–
1
8
00—400 cm and attributed to stretching and bending
two signals of the OCH groups added to positions a and b
2
vibrations of the С=С, Ph, CH , CH , and =CH groups.
(see Scheme 1) with the corresponding intensity ratio.
Additional nonequivalence of the chemical shifts of the
3
2
A characteristic feature of the IR spectra is the pair of
–
1
intense absorption bands at ~1600 and 1420 cm in the
spectra of all samples. The presence of these bands related
to antisymmetric (ν ) and symmetric (ν ) stretching vibraꢀ
signals of the OCH groups is observed for ester derivaꢀ
2
tives 3, 4 and potassium salts 5, 6. The signals of the H(4)
1
aromatic protons in the H NMR spectra coalesce with
as
s
2
9,30
tions of the carboxylate group, respectively,
the formation of ionized complex structures.
confirms
the temperature increase. Magnetic nonequivalence of
the protons of the ОСН groups is retained (Fig. 2). This
2
NMR spectroscopy represents very informative
methods for the determination of spatial structure of comꢀ
pounds. The signals in the NMR spectra of synthesized
compounds 3—8 were assigned on the basis of Н, С,
HSQC, and HMBC experiments (Table 1).
can be due to anisotropy of the chemical shift of the
carbonyl groups in the substituent itself and from the
adjacent groups. In calixarenes, unlike their monomeric
analogs, the substituents at the upper rim can experience
steric hindrances preventing the averaging in time of their
mutual orientations. In addition, the protons in the groups
pointed inside the cavity experience an additional upfield
shift induced by currents of the aromatic rings.
The presence of many polar groups at the upper rim
of calix[4]arenes 5 and 6 can result in the selfꢀassociation
of calix[4]arenes, which also can be a reason for the
nonequivalence of the chemical shifts of the protons of
the methylcarboxylate groups due to their different parꢀ
ticipation in hydrogen bonding.
1
13
Several isomeric forms (rccc, rctt, rcct, and rtct) are
possible for both calix[4]pyrogallols and calix[4]resorciꢀ
nols.31 The rcccꢀisomers are usually isolated when basal
calix[4]pyrogallols with alkyl substituents at the lower rim
are prepared, as in our case.32 These isomers are characꢀ
terized by the predomination of the averaged С4v symꢀ
metry, which is a result of fast equilibration between two
equivalent boat conformations with transition through the
3
3
cone conformation with the symmetry С . The study of
4
v
calix[4]resorcinols unsubstituted and functionalized at the
hydroxy groups of calix[4]resorcinols showed that the
To check the latter assumption, we measured the selfꢀ
diffusion coefficients by the NMR method with the pulse

Calix[4]pyrogallol polycarboxylic complexes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
85
–
1
3
5 to 0.5 mmol L , the D value remains unchanged,
s
T = 303 K
T = 323 K
T = 343 K
44
indicating the stability of the aggregated structures. This
does not allow us to determine D of the free monomeric
s
form using the standard dilution procedure.
2
1
The earlier study of the acidic properties of the
rcttꢀisomer of perꢀOꢀ(carboxymethyl)calix[4]pyrogallol
1
(
R = 4ꢀMeOC H ) showed that the formation of parꢀ
6
4
ticles was detected only to the decaanion under the
pHꢀmetric conditions. This acid dissociates most easily
by the first and second steps (pK = 5.05, pK = 4.98),
1
2
which is due to the formation of an intramolecular hydroꢀ
gen bond between the adjacent carboxymethylated
pyrogallol fragments. Its further dissociation by the third
(pK3,4 = 12.19), fourth (pK5,6 = 13.97), fifth (pK7,8 = 15.59),
and sixth (pK9,10 = 18.15) steps, which proceeds with
abstraction of immediately two protons, is substantially
impeded with an increase in the total charge of the acid.
A backward process is observed upon the dissolution
of potassium salt 5 in aqueous media: protonation of
the carboxylate groups determined by the pH value of the
medium. Unlike the rcttꢀisomer, in the rcccꢀisomer the
functional groups immobilized at different phenyl fragꢀ
ments are spatially approached, which should facilitate
their protonation due to the more efficient electrostatic
interaction and formation of intramolecular hydrogen
bonds. In the studied concentration range, solutions of
T = 363 K
7
6
5
4
3
2
δ
1
Fig. 2. H NMR spectra of potassium salt of calix[4]pyrogallol 5
at different temperatures in D O.
2
3
5—37
magnetic field gradient.
The obtained D value of
s
–
10
2 –1
2
.42•10
m s (R = 11.5 Å) is considerably lower
H
–
10
2 –1
than D = 3.27•10
m s (RH = 8.5 Å) theoretically
s
2
4
calculated by the HYDRONMR program. This value is
also lower than that for calixarenes with close geometric
sizes. For example, for the calix[4]resorcinol tetrasulfonate
derivative with the methyl substituents at the lower rim
experimental values D (3.50•10 m s ) and R (7.7 Å)
determined for aqueous solutions agree well with the theoꢀ
retical values: D = 3.73•10 m s and R = 7.4 Å.
According to available data,
molecules by 25—30% indicates the formation of a dimer.
salt 5 in D O were weakly alkaline (pH 7.2—8.7).
2
Thus, it can be assumed that a part of carboxylate
groups is transformed into the carboxy groups upon the
dissolution of potassium salt 5. The fact that calixarene
has a boat shape during dimer formation, indicating that
only some functional groups are involved in its formation
and the baskets in the dimer are shifted relative to each
other. For this mutual arrangement different from more
symmetric axial arrangement, a greater number of groups
3
8,39
the
–
10
2 –1
s
H
–
10
2 –1
s
H
4
0—43
the decrease in D of
s
When the concentration of compound 5 decreases from
H
O
C
Fig. 3. Optimized by the semiempirical method (AM1) model of the structure of dimer 5 stabilized by two K+ ions. Hydrogen atoms
not involving in bonding are omitted.

86
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Podyachev et al.
can participate in binding. In addition, in this case, the
destabilizing contribution of the electrostatic repulsion
from the charged carboxylate groups, which can be conꢀ
centrated predominantly on the parts of the baskets that
are mostly remote from each other and are not involved in
lence of bonds. All this reflects the difference in the
–
frequencies ∆ν(CO ) = ν – ν , which reaches the maxiꢀ
2
as
s
3
0,45
mum value at monodentate coordination.
However,
the multifactor character and many carboxylate groups,
whose absorption is overlapped, in the compounds under
study do not allow us to conclude unambiguously about
the coordination mode.
+
binding. The K ions present in solution can additionally
favor the electrostatic stabilization of similar structure
due to coordination with the charged parts of the molꢀ
The spectrum of the Fe L complex contained the
absorption of the carboxylate groups and also the highꢀ
4
ecules. We have previously2
0,21
shown that alkaline metal
ion in water—DMSO solutions form mononuclear comꢀ
plexes with perꢀOꢀ(carboxymethyl)calix[4]resorcinols
and ꢀpyrrogallols. The formation of binuclear complexes
was observed only for the calix[4]resorcinol pentaꢀ and
hexaanions. The model of the dimeric structure correꢀ
sponding to the above concepts is shown in Fig. 3.
frequency peak ν(С=О) with the absorption maximum
–
1
at 1740 cm , indicating the presence of nonionized
2
9
carboxylate groups. This is also confirmed by the differꢀ
ence spectra of compounds 10 and 5 exhibiting broad,
4
6
typically acidic absorption “hills” with maxima at ~3000
and 2500 cm– of the Fermi resonance νОН and overtones.
When Fe(NO ) excess was used instead of the equiꢀ
1
The addition of 12 equivalents of KOH to an aqueous
3
3
–
10
2 –1
solution of compound 5 increases D to 2.77•10 m s
molar amount of FeCl , a complex analogous to complex
s
3
(
R = 10.0 Å). When 12 equivalents of НCl are added, a
10 (according to the elemental analysis and IR spectral
data) was isolated. As already mentioned, the dissolution
of potassium salt 5 in aqueous media is accompanied
by the protonation of the carboxylate groups, and the
H
precipitate is formed and dissolved on heating. Therefore,
D was measured at higher temperature (T = 323 K).
Since the viscosity of water decreases on the temperature
rise, it is correct to compare only the hydrodynamic radii
of R . At the same time, the temperature rise should
s
4
7
3+
susceptibility to hydrolysis of the Fe salt can favor this
process. Taking into account the low relative intensity of
the ν(С=О) absorption band of the carboxy groups comꢀ
H
reduce the degree of aggregation. However, in the latter
case, R increases to 11.9 Å.
–
pared to the ν (СО ) band, we can assume that one or
H
as
2
Thus, an increase in the basicity of the medium shifts
the equilibrium from dimeric to monomeric structures,
and an increase in the acidity increases the degree of
aggregation. At the same time, not so substantial change
in the degree of aggregation of calix[4]pyrogallol 5 with
the variation of the concentration and pH of the medium
indicates that its dimeric form is stable.
two water molecules in the composition of the Fe L comꢀ
4
plex (10) are in the hydrolyzed form. The proton of the
water molecule is bound to one of the carboxylate groups,
and its hydroxy group is coordinated to the Fe3 ion.
+
The presence of hydroxy groups in the Fe L complex
4
(10) is confirmed by the broadened IR bands (see Fig. 1)
–
1
with absorption maxima at ~3390 and 3250 cm (ν(Н О))
2
and a dome at ~650 cm– (libration vibrations of bound
1
Spectral and structural features of complexes 9—11
according to IR and ESR spectroscopic data. Since the
solubility of the complexes is low, the IR and ESR spectra
were recorded only for their powders. As should be
expected, the IR spectra of complexes 9—11 (taking into
account their ionic character) are of the same type and
similar to the spectrum of the starting potassium salt 5.
However, more detailed analysis revealed some specific
features.
water) under a series of lowꢀfrequency peaks, which is
characteristic of water of crystallization.3
0,48
Analogous
components are observed in the spectra of the Cu L (9),
6
La L (11), and K L (5) complexes.
4
12
–
1
The highꢀfrequency (~3390 cm ) and lowꢀfrequency
–
1
(~3250 cm ) absorption ν(Н О) in the spectra of the
2
complexes can be due to the Fermi resonance ν(ОН) with
overtones, manifestation of ν (Н О) and ν (Н О), and
as
2
s
2
–
–1
The stretching vibration frequency ν (СО ) (1606 cm )
the presence of water molecules coordinated by different
as
2
–
30,46,49—51
in the spectrum of complex 5 is higher and the ν (СО )
modes.
s
2
–
1
frequency (1419 cm ) is lower than the corresponding
The ν(Н О) frequency values in the spectra of
2
frequencies in the spectra of complexes 9—11. In the
compounds 9—11 indicate the involvement of the water
2
+
3+
3+
considered Cu , Fe , and La complexes, the paramꢀ
molecules in rather strong (up to ~7 kcal per bond)
–
1
28,45—48
eters discussed are close, being ~1587 and 1423 cm ,
respectively. This indicates the formation of the bonds
with transition metal ions with the same strength but
somewhat different compared with those of the univalent
hydrogen bonds.
Evidently, the water molecules
–
–
are coordinated with the СО2 groups (СО ...Н О),
2
2
forming intraꢀ and intermolecular hydrogen bonds, and
also participate in coordination with metal cations.
As a whole, the broadened and smoothened absorpꢀ
tion bands in the IR spectra indicate the nonsymmetric
and distorted spatial structure of the complexes compared
to the ideal С4v symmetry. This is probably due to many
polar substituents at the upper rim of calix[4]pyrogallol.
+
К cation.
Proton abstraction from the carboxy group of carꢀ
boxylic acid results in the situation that the oxygen
atoms become equivalent. Monodentate or nonsymmetric
bidentate coordination of the metal ion can violate equivaꢀ

Calix[4]pyrogallol polycarboxylic complexes
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
87
T = 293 K
bonds. At room temperature the Fe L complex (10) is
4
3
+
characterized by the environment of the Fe ions close
2
+
2+
to octahedral. The strong antiferromagnetic Cu —Cu
interaction serves as the most probable reason for the
absence of signals in the ESR spectrum of the Cu L
6
complex (9).
T = 133 K
This work was financially supported by the Russian
Foundation for Basic Research (Project No. 07ꢀ03ꢀ00325a).
References
1
2
. Yu. V. Yablokov, V. K. Voronkova, L. V. Mosina, Paramagnitnyi
rezonans obmennykh klasterov [Paramagnetic Resonance
of Exchange Clusters], Nauka, Moscow, 1988, 181 pp. (in
Russian).
0
200
400
H/mT
Fig. 4. ESR spectra of solid sample 10 with the temperature
decrease from 293 to 133 K (∆T = 20 K).
. D. W. Smith, Ann. Rep. Progr. Chem., Sect. A, 2001, 97, 217.
The ESR spectrum of the Fe L complex (10) at room
3. The Chemistry of Carboxylic Acids and Esters, Ed. S. Patai,
London, 1969.
4. G. M. Larin, V. V. Minin, V. F. Shul´gin, Usp. Khim., 2008,
77, 476 [Russ. Chem. Rev. (Engl. Transl.), 2008, 77].
5. M. C. Bruzzoniti, E. Mentasti, C. Sarzanini, J. Chromatogr. B,
4
temperature is characterized by the single line with
5
2
g = 2.0 and a width of 73.5 mT (Fig. 4) corresponding to
3
+
5
the highꢀspin configuration Fe (3d ) with the environꢀ
ment of the Fe3+ ion close to octahedral. With the temꢀ
1
998, 717, 3.
. M. A. Kiskin, I. L. Eremenko, Usp. Khim., 2006, 75, 627
Russ. Chem. Rev. (Engl. Transl.), 2006, 75, 559].
. G. R. Choppin, A. Dadgar, E. N. Rizkalla, Inorg. Chem.,
986, 25, 3581.
perature decrease, the spectral line with g = 2.0 is broadꢀ
ened to 101 mT (at 133 K) with the simultaneous appearꢀ
ance and increase in the line intensity in the halved field.
The temperatureꢀdependent exchange elimination in the
magnetically condensed state or a symmetry decrease can
be assumed. The process is accompanied by an insignifiꢀ
cant decrease in the integral intensity of the spectra, which
is possibly related to antiferromagnetism of this complex.
6
7
[
1
8. G.ꢀQ. Bian, T. KurodaꢀSowa, H. Konaka, M. Hatano,
M. Maekava, M. Munakata, H. Miyasaka, M. Yamashita,
Inorg. Chem., 2004, 43, 4790.
9
. S. Kanegawa, S. Karasawa, M. Nakano, N. Koga, Chem.
Commun., 2004, 1750.
No ESR spectra of the Сu L complex (9) were
6
1
0. I. G. Fomina, A. A. Sidorov, G. G. Aleksandrov, T. B.
Mikhailova, E. V. Pakhmutova, V. M. Novotortsev, V. N.
Ikorskii, I. L. Eremenko, Izv. Akad. Nauk, Ser. Khim., 2004,
detected at room temperature or with the temperature
decrease down to 133 K. The lowꢀintensity line is
observed only at g = 2.0. The reduction of Cu2 to Cu
+
+
1
422 [Russ. Chem. Bull., Int. Ed., 2004, 53, 1477].
during complex formation can result in the absence of
signals. However, this assumption is not consistent with
the elemental analysis data, because the compensation of
charges of the carboxylate groups requires twofold larger
metal amount. Were the carboxylate groups transformed
into the uncharged carboxy groups, the latter would have
been observed in the IR spectrum of the complex. At the
11. V. I. Ovcharenko, R. Z. Sagdeev, Usp. Khim., 1999, 68, 381
[Russ. Chem. Rev. (Engl. Transl.), 1999, 68, 345].
12. M. Verdaguer, Polyhedron, 2001, 20, 1115.
1
3. C. D. Gutsche, Calixarenes Revisited: Monograph in Supramoꢀ
lecular Chemistry, Ed. J. F. Stoddart, The Royal Society of
Chemistry, Cambridge, 1998.
1
1
4. Calixarenes 2001, Eds Z. Asfary, V. Böhmer, J. Harrowfield,
J. Vicens, Kluwer Academic Publishers, Dordrecht, 2001.
5. S. N. Podyachev, V. V. Syakaev, S. N. Sudakova, R. R.
Shagidullin, D. V. Osyanina, L. V. Avvakumova, B. I.
Buzykin, Sh. K. Latypov, W. D. Habicher, A. I. Konovalov,
J. Incl. Phenom., 2007, 58, 55.
1
2+
same time, it is known that Cu carboxylates (for
example, Cu2+ benzoates and acetates with the lantern
2
+
2+
shape) are characterized by the direct Cu —Cu bond
with the strong antiferromagnetic interaction. It is most
likely that this is a reason for the absence of signals in the
ESR spectrum of complex 9 under our conditions.
Thus, the structures of transition metal complexes
16. S. N. Podyachev, S. N. Sudakova, V. V. Syakaev, A. K.
Galiev, R. R. Shagidullin, A. I. Konovalov, Supramol. Chem.,
2
008, 20, 479.
1
1
7. K. Ohto, M. Yano, K. Inoue, T. Yamamoto, M. Goto,
F. Nakashio, S. Shinkai, T. Nagasaki, Anal. Sci., 1995, 11, 893.
8. K. Ohto, M. Yano, K. Inoue, T. Yamamoto, T. Nagasaki,
M. Goto, F. Nakashio, S. Shinkai, Polyhedron, 1997, 16,
9
—11 are of the same type and differ from ideality: their
structures are more distorted than that of potassium salt of
calix[4]pyrogallol 5. The carboxylate groups form approxiꢀ
mately equal in strength bonds with transition metal ions
that are stronger than the bonds in the case of the univaꢀ
1
655.
19. M. H. B. Grote Gansey, W. Verboom, F. C. J. M. van Veggel,
V. Vetrogon, F. ArnaudꢀNeu, M.ꢀJ. SchwingꢀWeill, D. N.
Reinhoudt, J. Chem. Soc., Perkin Trans. 2, 1998, 2351.
+
lent К cation. All studied complexes of calix[4]pyrogallols
contain water molecules bound by rather strong hydrogen

88
Russ.Chem.Bull., Int.Ed., Vol. 58, No. 1, January, 2009
Podyachev et al.
2
2
0. S. N. Podyachev, A. R. Mustafina, W. D. Habicher, Izv.
Akad. Nauk, Ser. Khim., 2003, 70 [Russ. Chem. Bull., Int.
Ed., 2003, 52, 73].
1. S. N. Podyachev, A. R. Mustafina, A. N. Kopeele,
M. Grüner, W. D. Habicher, B. I. Buzykin, A. I. Konovalov,
Izv. Akad. Nauk, Ser. Khim., 2004, 1134 [Russ. Chem. Bull.,
Int. Ed., 2004, 53, 1181].
2. H. Budig, R. Paschke, S. Diele, I. Letko, G. Pelzl, Ber.
BunsenꢀGes. Phys. Chem., 1993, 97, 1355.
3. T. Gerkensmeier, C. Agena, W. Iwanek, R. Froehlich, S. Kotila,
C. Naether, J. Mattay, Z. Naturforsch. B, 2001, 56, 1063.
4. J. G. de la Torre, M. L. Huertas, B. Carrasco, J. Magn.
Reson., 2000, 147, 138.
37. P. S. Pregosin, P. G. A. Kumar, I. Fernández, Chem. Rev.,
2005, 105, 2977.
38. E. Kh. Kazakova, V. V. Syakaev, Ju. E. Morozova, N. A.
Makarova, L. A. Muslinkina, G. A. Evtugin, A. I. Konovalov,
J. Incl. Phenom. Macroc. Chem., 2007, 59, 143.
39. V. V. Syakaev, A. R. Mustafina, J. G. Elistratova, Sh. K.
Latypov, A. I. Konovalov, Supramol. Chem., 2008, 20, 453.
40. A. S. Altieri, D. P. Hinton, R. A. Byrd, J. Am. Chem. Soc.,
1995, 117, 7566.
41. V. V. Krishnan, J. Magn. Reson., 1997, 124, 468.
42. P. R. Wills, Y. Georgalis, J. Phys. Chem., 1981, 85, 3978.
43. J. G. De la Torre, V. A. Q. Bloomfield, Rev. Biophys., 1981,
14, 81.
2
2
2
2
2
5. Chem3D, Cambridge Soft Corporation; http://www.camsoft.com.
6. Computational Chemistry, HyperChem Manual, Hypercube
Inc., Waterloo, Ontario, Canada, 2002.
7. HyperChem 7.03 Molecular Mechanics and Quantum Chemiꢀ
cal Calculations Package, HyperCub Inc., Canada, 2002.
8. S. N. Podyachev, I. A. Litvinov, A. R. Mustafina, R. R.
Shagidullin, W. D. Habicher, A. I. Konovalov, Izv. Akad.
Nauk, Ser. Khim., 2005, 614 [Russ. Chem. Bull., Int. Ed.,
44. A. Macchioni, G. Ciancaleoni, C. Zuccaccia, D. Zuccaccia,
Chem. Soc. Rev., 2008, 37, 479.
45. T. V. Koksharova, I. S. Gritsenko, I. V. Stoyanova, Zh.
Obshch. Khim., 2007, 77, 1564 [Russ. J. Gen. Chem. (Engl.
Transl.), 2007, 77, 1635].
46. A. V. Iogansen, Spectrochim. Acta, Part A, 1999, 55, 1585.
47. O. Yu. Pykhteev, A. A. Efimov, L. N. Moskvin, Zh. Neorg.
Khim., 1998, 43, 67 [Russ. J. Inorg. Chem. (Engl. Transl.),
1998, 43, 60].
2
2
2
005, 54, 623].
2
9. L. J. Bellamy, The InfraꢀRed Spectra of Complex Molecules,
Methuen and Co Ltd. (London)—J. Wiley and Sons
48. G. C. Pimentel, A. L. McClellan, The Hydrogen Bond, San
Francisco—London, 1960.
(
New York), 1957.
49. A. V. Karyakin, G. A. Kriventsova, Sostoyanie vody v
organicheskikh i neorganicheskikh soedineniyakh [State
of Water in Organic and Inorganic Compounds], Nauka,
Moscow, 1973, 176 pp. (in Russian).
50. L. H. Little, Infrared Spectra of Adsorbed Species, Academic
Press, London—New York, 1966.
3
3
0. K. Nakamoto, Infrared Spectra of Inorganic and Coordination
Compounds, J. Wiley and Sons, New York—London, 1962.
1. C. D. Gutsche, in Calixarenes 2001, Eds Z. Asfari, V. Böhmer,
J. Harrowfield, J. Vicens, Kluwer Academic Publishers,
Dordrecht—Boston—London, 2001, 10.
3
3
2. W. Sliwa, T. Zujewska, B. Bachowska, Pol. J. Chem., 2003,
51. Th. Steiner, Angew. Chem., Int. Ed. Engl., 2002, 41, 48.
52. H. A. Kuska, M. T. Rogers, in Radical Ions, Eds E. T.
Kaiser, L. Kevan, Wiley Interscience, New York, 1968.
7
7, 1079.
3. L. Abis, E. Dalcanale, A. Du Vosel, S. Spera, J. Chem. Soc.,
Perkin Trans. 2, 1990, 2075.
3
3
3
4. J. R. Fransen, P. J. Dutton, Can. J. Chem., 1995, 73, 2217.
5. E. O. Stejskal, J. E. Tanner, J. Chem. Phys., 1965, 42, 288.
6. P. Stilbs, Prog. Nucl. Magn. Reson. Spectrosc., 1987, 19, 1.
Received May 23, 2008;
in revised form September 22, 2008