Dinuclear Copper(II) Complexes
bardment (FAB) mass spectra were run with a Micromass-VG N 8.54. UV/Vis: λmax [ε (–1 cm–1 per 2Cu)] = 627 [500], 425
70SE instrument (2-nitrobenzyl alcohol matrix) and infrared spec-
tra with a Perkin–Elmer Spectrum One FT spectrometer furnished
with a Universal ATR sampling accessory. EPR spectra were ob-
tained with a Varian E-12 X-band instrument, calibrated near g =
2 with DPPH, and NMR spectra with Varian INOVA 300 and
500 MHz spectrometers. Optical spectra were obtained with a Per-
kin–Elmer Lambda-35 spectrophotometer; samples in DMF for
the 450–1,000 nm region were diluted into MeOH for the UV. Vari-
able-temperature magnetic susceptibility data were collected in the
range 2–290 K using a Quantum Design SQUID magnetometer,
employing a main solenoid field of 1 T and a gradient field of
10 Tm–1. Samples were placed in aluminum or gelatin capsules in-
side 5-mm plastic straws. Susceptibility data were corrected for dia-
magnetism using Pascal’s constants,[26] Co[Hg(SCN)4] being used
as a calibration standard. Data were fitted on a Macintosh G5
platform, using the Microsoft Excel Solver and the statistical macro
Solvstat.[27] X-ray data sets for the complexes 1 and 2 were collected
at 100 K with a Bruker AXS SMART APEX CCD diffractometer,
using Mo-Kα radiation (λ = 0.71073 Å, µ = 7.08 cm–1) in the ω
scan mode. Structure solution and refinement were performed
using SHELXTL.[28] Both structures were solved by direct methods
and all non-hydrogen atoms were refined anisotropically. Hydroxy
hydrogen atoms in 1 were located in difference density Fourier
maps and all O–H distances were restrained to be the same (within
a standard deviation of 0.02 Å). The hydroxy H-atom H9b in 2 was
located similarly and its O–H distance was restrained to be
0.84(2) Å. The other two O–H hydrogen atoms were placed in cal-
culated positions, but were allowed to rotate around the oxygen
atom to best fit the experimental electron density; a like procedure
was applied to the methyl groups. All other hydrogen atoms in both
structures were placed in calculated positions and refined with an
isotropic displacement parameter of 1.5 (methyl, hydroxy) or 1.2
times (all others) that of the adjacent C, O or N atom.
Preparation of Schiff Base Ligands: The ligands H4LMe and H4LEt
were prepared by first dissolving thiocarbohydrazide (0.265 g,
2.5 mmol) in 20 mL of H2O/EtOH (1:3). The 3-alkoxy-2-hydroxy-
benzaldehyde (5 mmol) in 25 mL of EtOH was then added to this
solution, and the resulting reaction mixture was refluxed for 1 h.
The pale yellow solids which formed were filtered off, washed with
ethanol, diethyl ether and dried in air. Yields were 85–95%.
Bis(3-methoxysalicylaldehyde) Thiocarbohydrazone (H4LMe): Yel-
low powder. MS: m/z = 375.1 [MH+]. C17H18N4O4S (374.4): calcd.
C 54.5, H 4.86, N 15.0; found C 54.5, H 5.19, N 15.4. 1H NMR
([D6]DMSO): δ = 3.79 (s, 6 CH3), 6.64 (s, OH/NH), 6.82 (d, 2 H,
m), 6.84 (d, 4 H, o/p), 8.51 (s, 1 H, imine), 8.71 (s, 1 H, imine) ppm.
Bis(3Ј-ethoxysalicylaldehyde) Thiocarbohydrazone (H4LEt): Yellow
powder, MS: m/z = 403.1 [MH+]. C19H22N4O4S (402.5): calcd. C
56.7, H 5.52, N 13.9; found C 56.4, H 5.70, N 14.2. 1H NMR ([D6]-
DMSO): δ = 1.33 (t, J = 4.2 Hz, 6 CH3), 4.04 (q, J = 4.2 Hz, 4
CH2), 7.63 (s, OH/NH), 6.81 (d, 2 H, m), 6.99 (d, 4 H, o/p), 8.52
(s, 1, imine), 8.72 (s, 1 H, imine) ppm.
[1.8ϫ104], 400 sh [1.6ϫ104], 337 sh [2.2ϫ104], 306 [3.4ϫ104], 236
[3.2ϫ104], 205 nm [3.7ϫ104].
The copper complex 2 was obtained as a brown crystalline solid
after air-drying. Cu2(HLEt)(HSO4)·0.5MeOH·3.5H2O; C19.5H29-
Cu2N4O12S2 (703): calcd. C 33.3, H 4.17, N 8.00; found C 33.5, H
3.64, N 8.11. UV/Vis: λmax [ε (–1 cm–1)] = 628 [470], 425 [1.9ϫ104],
400 sh [1.6ϫ104], 340 sh [2.1ϫ104], 304 [3.4ϫ104], 236 [3.3ϫ104],
208 nm [3.7ϫ104].
CCDC-665237 (for 1) and -665236 (for 2) contain the supplemen-
tary crystallographic data for this paper. These data can be ob-
tained free of charge from the Cambridge Crystallographic Data
Center via www.ccdc.cam.ac.uk/datarequest/cif.
Acknowledgments
This work was supported by the U.S. Civilian Research & Develop-
ment (follow-on award to D. D., MTFP-022/05), Foundation’s
Moldovan Research, and Development Association (MRDA/
CRDF). A. W. A. thanks Drexel University for support, and we
thank Dr. D. Radisic for assistance with mass spectra.
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Synthesis of Copper(II) Complexes: A suspension of the appropriate
Schiff base ligand (0.25 mmol) and CuSO4·5H2O (0.125 g,
0.5 mmol) in 25 mL of methanol was heated to reflux and stirred
for 10 min. The brown crystalline solid which formed on cooling
was filtered off, washed with methanol and placed in a capped vial.
Samples for magnetochemistry were further air-dried. Yields were
60–65%.
The copper complex 1 was obtained as a brown crystalline solid
after air-drying. Cu2(HLMe)(HSO4)·MeOH·3H2O. C18H26Cu2N4-
O12S2 (682): calcd. C 31.7, H 3.85, N 8.22; found C 31.9, H 3.50,
Eur. J. Inorg. Chem. 2008, 2530–2536
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