ZINC COMPLEXES
33
triazole in 10 mL of 96% ethanol. The resulting reacꢀ selected crystallographic data are shown in Table 1.
tion mixture was stirred under heating with a magnetic Semiꢀempirical correction for absorption was applied
stirrer for 1 h. To the suspension formed, 2 mmol of (0.8646/0.7723 for
I, 0.8982/0.8527 for II, and
zinc acetate dihydrate was added, and the mixture was 0.8827/0.7132 for IV) [9]. The structures were solved
stirred for 2 h. The precipitate was kept under the by the direct method and refined by fullꢀmatrix leastꢀ
mother liquor for 12 h, then filtered off, washed with squares in the anisotropic approximation (SHELXꢀ
ethanol, and dried in air. The product was obtained as 97) [10]. Crystallographic data for compounds I, II,
520–660 mg of a yellow crystalline substance; triazole and IV have been deposited with the Cambridge Crysꢀ
yield, 65–75%.
tal Database, nos. 733658, 733659, and 7333660,
respectively, and can be free downloaded from the site
The zinc content was calculated from complexoꢀ
metric titration data [7] after thermal decomposition
of the test sample; the nitrogen content was deterꢀ
mined by the Dumas method [8].
IR spectra of the complexes were recorded as KBr
pellets in the range of 400–4000 cm–1 on a Nicolet
Nexus 470 FTIR spectrometer.
RESULTS AND DISCUSSION
Our studies show that the products of condensation
of salicylaldehyde and 3ꢀ(pyridine)ꢀ5ꢀ(2ꢀaminopheꢀ
nyl)ꢀ1Hꢀ1,2,4ꢀtriazoles react with zinc acetate to
form molecular complexes with the metal : ligand ratio
of 1 : 1. The complexes are stable up to 40–50°С, and
a further increase in temperature leads to desolvation
of the complexes. A crystallization ethanol molecule
1
·
For
0.5EtOH (C41H29N10O2.5Zn2) (I),
Zn2L2
anal. calcd. (wt %): Zn, 15.59; N, 16.66.
Found (wt %): Zn, 15.62; N, 16.36.
IR (cm–1) for
I
: 1610 (
1457, 1444, 1330, 1147, 800, 752.
For [ZnL2]
EtOH (C22H21N5O2Zn) (III), anal.
ν(C=NSchiff)), 1593, 1533,
entering the composition of complex
40 100 without noticeable thermal features. The
ethanol molecule of compound III is eliminated at a
higher temperature (50–180 ). The process is
accompanied by a small exotherm on the DTA curve
with a maximum at 70 . At 235 , complex III melts.
Thermal oxidative destruction of triazoles is observed
(at 230 and 300 for complexes and III, respecꢀ
tively, followed by combustion of the organic residue.
The process is completed at 650–700
The IR spectra of complexes and III do not conꢀ
I is removed at
–
°С
·
calcd. (wt %): Zn, 14.47; N, 15.48.
°С
Found (wt %): Zn, 14.09; N, 15.71.
IR (cm–1) for III: 1614 (
ν(C=NSchiff)), 1577, 1535,
°С
°С
1467, 1444, 1321, 1153, 754.
Thermogravimetric experiments were performed on
a PaulikꢀPaulikꢀErdey Qꢀderivatograph in an open
ceramic crucible under a static air atmosphere with
heating at a rate of 10 K/min; the standard was a calꢀ
cined aluminum oxide sample.
Absorption spectra were recorded on a Perkinꢀ
Elmer Lambdaꢀ9 UV/VIS/NIR spectrophotometer.
Luminescence spectra of solid samples were obtained
with a LOMO SDLꢀ1 spectrometer equipped with a
FEUꢀ79 photomultiplier.
Excitation and luminescence spectra of solutions
were recorded on a Horiba JobinꢀYvon FluorologꢀFL
3ꢀ22 spectrophotometer equipped with a 450 W Xe
lamp.
Xꢀray crystallography measurements were perꢀ
formed using a Bruker ApexꢀII CCD diffractometer
°С
I
°С.
I
tain bands corresponding to the stretching vibrations
of N–H and O–H groups, which are observed in the
IR spectra of the ligands at 3380 and 3270 cm–1,
respectively. The coordination of the phenoxyl oxygen
atom is accompanied by a shift of the band of the stretchꢀ
ing vibrations of the Cphen–O bond from 1290 cm–1 in
the free triazoles to 1330–1321 cm–1 in the complexes.
A shift of the band of the stretching vibrations of the
⎯
HC=N– bond by 15–20 cm–1 to the shortwave
range is indicative of the coordination of the imine
nitrogen atom.
According to Xꢀray crystallography, complex
I is
binuclear (Fig. 1). Each zinc ion is coordinated by two
pentadentate bridging ligands in the doubly deprotoꢀ
nated form. Each central atom has a distorted tetragoꢀ
nalꢀbipyramidal environment formed by four nitrogen
atoms in the base of the pyramid and an oxygen atom
in the axial position. The Zn2N4 central sixꢀmembered
metal ring has a boat conformation. The Zn(1) and
Zn(2) atoms deviate by 0.48 Å and 0.65 Å, respectively,
to the apical oxygen atoms from the plane of the four
nitrogen atoms. The intramolecular Zn···Zn distance is
4.038Å, which is characteristic of binuclear complexes
of 1,2,4ꢀtriazoles [1]. The planar configuration and
deprotonation of the 1,2,4ꢀtriazole moiety facilitate
delocalization of C=N double bonds in the N3С2 fiveꢀ
membered ring. Because of this, the N(2)–N(3) bond
(
МоКα radiation, graphite monochromator, λ =
0.71073 Å). Single crystals of the zinc complex with
3ꢀ(pyridineꢀ2ꢀyl)ꢀ5ꢀ(2ꢀsalicylideneiminophenyl)ꢀ1Hꢀ
1,2,4ꢀtriazole were obtained by recrystallization from
a DMSO–ethanol mixture (2 : 1 vol/vol), as well as
from dioxane. The compositions of single crystals
grown from DMSO–ethanol and dioxane were
1
1
· 2C4H8O2 · 2H2O
Zn2L2
·
0.5EtOH (
I) and
Zn2L2
(
II), respectively. Single crystals of the zinc complex
with 3ꢀ(pyridineꢀ4ꢀyl)ꢀ5ꢀ(2ꢀsalicylideneiminopheꢀ
nyl)ꢀ1Hꢀ1,2,4ꢀtriazole were obtained by slow diffuꢀ
sion of chloroform vapors into a pyridine solution of
complex III. The crystal composition is formulated as
{[ZnL2(Ру)]
· CHCl3}n (IV). Experimental details and
RUSSIAN JOURNAL OF INORGANIC CHEMISTRY Vol. 56 No. 1 2011