Dinuclear copper(II) complexes with bis-thiocarbohydrazone ligands

Article abstract of DOI:10.1002/ejic.200701187

Copper(II) complexes with substituted bis(salicylaldehyde) thiocarbohydrazones (3-methoxy = H₄L^Me, 3-ethoxy = H ₄L^Et), have been synthesized. These ditopic ligands form dinuclear copper(II) complexes containing

Full text of DOI:10.1002/ejic.200701187

FULL PAPER
DOI: 10.1002/ejic.200701187
Dinuclear Copper(II) Complexes with Bis-thiocarbohydrazone Ligands
Diana Dragancea,[a] Anthony W. Addison,*[b] Matthias Zeller,[c] Laurence K. Thompson,[d]
Dushyanthi Hoole,[b] Mihail D. Revenco,[a] and Allen D. Hunter[c]
Dedicated to the memory of Prof. N. V. Gerbeleu
Keywords: Thiocarbohydrazone / Copper / Antiferromagnetism / Dinuclear complexes / Schiff bases
Copper(II) complexes with substituted bis(salicylaldehyde)
thiocarbohydrazones (3-methoxy = H4LMe, 3-ethoxy = H4LEt),
have been synthesized. These ditopic ligands form dinuclear
copper(II) complexes containing the ligands in their triply
deprotonated forms. The ligands entail two nonequivalent
donor atom sites (ONN and ONS) for copper(II) coordination.
Magnetic measurements of the complexes in the tempera-
ture range 2–290 K showed significant antiferromagnetic in-
teractions between the two copper(II) ions, with –2J around
180 cm–1. The dinuclear molecules in turn also form face-to-
face H-bonded dimers involving four coppers in total.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2008)
ported.[11] In these 24-membered metallomacrocycles, the li-
gand used its maximal donor capacity in a manner unprece-
dented for thiocarbohydrazone coordination chemistry.
Continuing our work[11] on the coordination chemistry of
bis(salicylaldehyde) thiocarbohydrazones, we have now pre-
pared new copper(II) complexes, in order to establish the
influence of the phenyl ring substituents on their nuclearity,
geometry and magnetic properties. The substituents were
placed at strategic positions with respect to the donor sets,
Introduction
During the last several years numerous papers dealing
with compounds that are able to coordinate to two or more
metal atoms have been published. Such centres are found
in biological systems, e. g. ferritin,[1,2] while those with high-
spin ground states can act as single-molecule magnets,[3,4]
and some of them exhibit spin-transition behavior,[5] or
manifest catalytic activity.[6]
Thiocarbohydrazide and its hydrazone Schiff bases con-
stitute interesting ligand systems because of their versatile
coordination ability toward metals. Thiocarbohydrazones
have previously been used as building blocks in the self-
assemblage of tetranuclear molecular square structures. In
particular, mixed-valence iron(II)/(III), nickel(II), zinc(II)
and cadmium(II) clusters have been synthesized starting
from 1,5-bis(2-acetylpyridine)thiocarbohydrazone or re-
lated derivatives.[7–9] Reactions of the same ligands with
copper(II) produced dimers of dimeric units held together
by extraneous bridging ligands.[9,10] Recently, two azine-
bridged octanuclear copper(II) complexes, assembled from
bis(2-hydroxybenzaldehyde) thiocarbohydrazone were re-
[a] Laboratory of Coordination Chemistry, Institute of Chemistry,
Academy of Sciences,
Academiei str. 3, 2028 Chisinau, Moldova
[b] Chemistry Department, Drexel University,
Philadelphia, PA 19104-2875, USA
Fax: +1-215-895-1265
E-mail: AddisonA@drexel.edu
[c] STaRBURSTT – Cyberdiffraction Consortium and Chemistry
Department, Youngstown State University,
Youngstown, OH 44555-3663, USA
E-mail: adhunter@ysu.edu
[d] Chemistry Department, Memorial University,
St. John’s, NL, A1B 3X7, Canada
Scheme 1.
2530
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2530–2536

Dinuclear Copper(II) Complexes
modifying the electronic environment around the metal cen- complexes 1 (methoxy) and 2 (ethoxy). Despite the presence
ters (Scheme 1). In addition, we eschewed the use of added of the solvophilic alkoxy groups, they are insoluble in non-
base, reasoning that the degree of self-association of the polar organic solvents, but soluble in polar coordinating
dicopper units may become limited by retention of protons solvents like DMF and DMSO and modestly soluble in
on groups that act as bridging donors in the octanuclear MeOH. Figure 1 shows the FAB-mass spectra which of-
systems.[11] The crystal and molecular structures of these fered the first confirmation of their dinuclear natures. Weak
complexes [Cu2(HLMe,Et)(HSO4)(MeOH)2]·MeOH have peaks corresponding to the tetranuclear species of atom
been determined by single-crystal X-ray diffraction.
composition [Cu4(HLEt)2(HSO4)]+ (1148) and [Cu4(HLEt)2-
(H)]+ (1052) were also seen.
Results and Discussion
3. Properties of the Compounds
1. Synthesis and Characterization of the Ligands
Both complexes are deep brownish-green, forming essen-
tially black crystals, and were obtained from the initial syn-
theses in crystalline forms [Cu2(HLMe,Et)(HSO4)(MeOH)2]·
MeOH suitable for X-ray crystallography. However, it be-
came evident that the methanol of crystallization is rather
readily lost on exposure of the crystals to the atmosphere at
ambient temperature, and is replaced by atmospheric water
molecules, without visible effect on the crystal morphology.
For the X-ray diffraction experiments, we were able to han-
dle the crystals so as to avoid solvent loss or exchange.
The slightly photosensitive Schiff base ligands H4LMe,Et
(Scheme 1) were prepared by treatment of the salicylalde-
hyde derivatives with thiocarbohydrazide taken in a 2:1 mo-
lar ratio in refluxing ethanol and have been characterized
1
by elemental analysis and H NMR spectroscopy. In the
NMR, the -NH and -OH are labile, while expression of the
imine-H as two resonances presumably reflects the isomer-
ism in Scheme 1. A recent report[12] includes reference to
unpublished structural data (CCDC-247503) for the meth-
oxy ligand H4LMe
.
Optical Spectra
The electronic spectra (vide infra) of the two compounds
in DMF/MeOH solution are of course quite similar. A
band near 630 nm (in DMF), although principally d–d in
nature, is somewhat enhanced in intensity, as is often ob-
served when sulfur donors are present;[13] in MeOH, this
band’s maximum shifts 10 nm bathochromically and its ap-
parent intensity is decreased about 10%. A more intense
envelope is present around 415 nm, to which the main con-
tribution is attributed to LMCT. Ligand-localised (π–π*)
bands appear near 295 and 230 nm.
2. Synthesis and Characterization of Copper(II) Complexes
Copper(II) complexes of the general formula
[Cu2(HLMe,Et)(HSO4)(MeOH)2]·MeOH were prepared by
combination of copper(II) sulfate with the appropriate li-
gand in methanol as the reaction medium. Use of a 2:1 Cu/
ligand molar ratio permitted the isolation of the dinuclear
Infrared Spectra
The IR spectra of all these compounds have considerable
spectral density in the 600–1650 cm–1 region. Chromo-
phores of interest which change frequency on coordination
are exemplified by reference to the methoxy-substituted
case. In H4LMe there is a sharp but weak band at 1612 cm–1,
which we assign as νC=N, and which shifts to 1598 cm–1 in
the copper complex, gaining substantially in intensity, in
the manner previousy noted.[14] A sharp band of medium
intensity at 815 cm–1 in H4LMe is attributed to mainly νC=S
character, and is absent from the copper complexes, where
a band of similar width and intensity now appears at
782 cm–1. This is quite consistent with the shift normally
observed[15,16] on coordination of a conjugated thione, asso-
ciated with the increased contribution of the thiolate reso-
nance form (Scheme 1).
Figure 1. FAB-MS of the two compounds, showing (upper) super-
4. Structures of Complexes
position of [Cu2HLMe +
]
and [Cu2H2LMe +
]
at m/z = 498, 499, with
[Cu2H2LMeHSO4]+ at m/z = 595, and (lower) superposition of
Comparison of H4LMe with its triply deprotonated, coor-
dinated form, shows that the free ligand[12] reconforms to
accommodate the two coppers.
[Cu2HLEt]+ and [Cu2H2LEt]+ at m/e = 526, 527, and [Cu2H2–4
-
LEtHSO4]+ species centred around m/z = 625. Electron capture by
Cu is implied.
Eur. J. Inorg. Chem. 2008, 2530–2536
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2531

A. W. Addison et al.
FULL PAPER
The lower aryl group (Figure 2) rotates by ca. 180°
around its C(aryl)–C(aldimine) bond to make its phenolic
oxygen atom O(2) available to form a six-membered metallo-
cycle including the hydrazone nitrogen atom N(4). Conse-
quently, the hydrazine–N(2) associated with the upper
phenylhydrazone moiety becomes deprotonated and forms
the five-membered chelate ring N2–C9–N3–N4–Cu. In
H4LMe the two benzene rings are ca. 10° from being copla-
nar, whereas in the complex, this dihedral angle is reduced
to less than 1°. Two tautomeric forms are possible for
H4LMe,Et: the thione form and thiol form (Scheme 1), which
are in equilibrium.[17] The thiol tautomer can adopt a syn
or anti configuration as a consequence of the double-bond
character of the central N–C linkage (Scheme 1). These
structures indicate that such ligands are potentially ditopic,
and indeed, dinucleation has been proposed previously[18]
for a copper complex of somewhat different composition,
but prepared from bis(2-hydroxy-3-methoxybenzaldehyde)
thiocarbohydrazone. X-ray diffraction reveals that in 1 and
2 the thiocarbohydrazone ligands adopt the thiol anti con-
figuration and thus provide two tridentate sites, one with
NNO and the other with ONS donor atoms, each of which
can accommodate one copper(II) ion (Figure 1). Thus, six
donor atoms of triply deprotonated ligand HL3– are bound
to two metal ions and give a dicopper(II) unit [Cu2L]+.
Consonant with the shift from thione-hydrazine toward
Figure 2. Comparison of the conformation of the free ligand
H4LMe with its HLMe3– copper complex. Only the coppers’ chelat-
ing agent donors are shown.
Another uncommon feature is that the sulfate ion is actu-
thiol-imine form,[16] the C–S bond length increases from ally bound as a hydrogen sulfate ligand. Its proton is stabi-
1.68 Å in the free ligand to 1.71 Å in the copper complex, lised by hydrogen-bonding interactions with the phenolate
and the C–N bond complementarily shortens from 1.34 Å and methoxy oxygen atoms. In the methoxy compound
to 1.325 Å. In the dinuclear 3-methoxysalicylaldehyde-de- these O–O distances are respectively 2.630 Å and 2.875 Å.
rived complex 1 (Figure 3), the left-hand Cu1 is square These complexes were prepared without addition of any
planar, with phenolate-O, aldimine-N, methanol-O and base; it is notable that sulfate acts as a base, with respect to
thiocarbonyl-S as the donors. The CuII are tightly bound, deprotonation of the hydrazine-N. There are about a dozen
–
with Cu–N, Cu–O distances around 1.96Ϯ0.07 Å, and Cu– instances of unidentately coordinated HSO4 in the litera-
S of 2.23 Å in their principal coordination plane.
ture, mostly with silver(I), while the compounds we report
The right-hand Cu2 is square pyramidal (τ = 0.07[13]), here add to the only two other copper examples so far
with methanol-O in the apical position. In the basal plane structurally characterised.[19] Meanwhile, there is a lattice
are imino-N, phenolate-O, sulfate-O and deprotonated (hy- methanol which is also H-bonded to an HSO4– oxygen (O–
drazide) N from the left-hand hydrazine unit.
O of 2.665 Å) (Table 1, Table 2 and Table 3).
Figure 3. Molecular structure of complex 1 (thermal ellipsoids at 50% level).
2532
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2530–2536

Dinuclear Copper(II) Complexes
Table 1. Crystallographic data for complexes 1 and 2.
Table 3. Selected bond angles [°] for complexes 1 and 2.
Complex 1
Complex 2
Angles
Complex 1 Angles
Complex 2
O(2)–Cu(1)–N(1) 95.15(6)
O(2)–Cu(1)–O(9) 85.13(5)
Crystal
Dimensions [mm]
Chemical formula
black hexagon
0.20ϫ0.20ϫ0.20
C20H28Cu2N4O11S2
black block
0.55ϫ0.36ϫ0.29
C22H32Cu2N4O11S2
719.72
monoclinic, P21/c
7.6352(4)
17.5330(9)
20.8504(10)
96.4590(10)
2773.5(2)
O(3)–Cu(1)–N(1)
O(3)–Cu(1)–O(6)
N(1)–Cu(1)–O(6)
O(3)–Cu(1)–S(3)
N(1)–Cu(1)–S(3)
O(6)–Cu(1)–S(3)
O(2)–Cu(2)–N(4)
O(2)–Cu(2)–O(7)
N(4)–Cu(2)–O(7)
O(2)–Cu(2)–N(2)
94.68(9)
86.64(8)
170.54(10) N(1)–Cu(1)–O(9) 169.61(6)
Formula weight [M] 691.66
176.60(6)
87.03(7)
92.16(6)
90.98(8)
87.93(8)
167.07(9)
171.52(8)
O(2)–Cu(1)–S(3) 174.14(4)
N(1)–Cu(1)–S(3) 86.97(4)
O(9)–Cu(1)–S(3) 93.78(4)
O(3)–Cu(2)–N(4) 90.57(6)
O(3)–Cu(2)–O(5) 88.27(6)
N(4)–Cu(2)–O(5) 167.35(7)
O(3)–Cu(2)–N(2) 171.33(6)
N(4)–Cu(2)–N(2) 80.95(6)
O(5)–Cu(2)–N(2) 99.60(6)
Crystal system
a [Å]
b [Å]
c [Å]
monoclinic, P21/c
7.4249(5)
17.3274(12)
20.2649(14)
96.5240(10)
2590.3(3)
100(2)
β [°]
V [Å3]
Temperature [°C]
Z
100(2)
4
N(4)–Cu(2)–N(2) 81.18(9)
4
O(7)–Cu(2)–N(2)
O(2)–Cu(2)–O(5)
N(4)–Cu(2)–O(5)
O(7)–Cu(2)–O(5)
N(2)–Cu(2)–O(5)
98.98(8)
97.09(8)
93.88(8)
99.04(8)
86.72(8)
Table 2. Selected bond lengths [Å] for complexes 1 and 2.
Bond lengths
Complex 1
Bond lengths Complex 2
Cu(1)–O(3)
Cu(1)–N(1)
Cu(1)–O(6)
Cu(1)–S(3)
Cu(2)–O(2)
Cu(2)–N(4)
Cu(2)–O(7)
Cu(2)–N(2)
Cu(2)–O(5)
C(9)–S(3)
1.8941(18)
1.955(2)
1.982(2)
2.2295(7)
1.9227(19)
1.941(2)
1.9648(19)
2.034(2)
2.416(2)
1.712(3)
1.325(3)
1.350(3)
Cu(1)–O(2)
Cu(1)–N(1)
Cu(1)–O(9)
Cu(1)–S(3)
Cu(2)–O(3)
Cu(2)–N(4)
Cu(2)–O(5)
Cu(2)–N(2)
Cu(2)–O(10)
C(10)–S(3)
C(10)–N(2)
C(10)–N(3)
1.8930(12)
1.9496(14)
1.9712(13)
2.2381(5)
1.9094(13)
1.9407(14)
1.9648(13)
2.0296(14)
2.5464(13)
1.7170(17)
1.331(2)
Each dinuclear moiety, though substantially planar, has
the coordinated methanol protruding from the plane, so
that its H-atom is H-bonded to the phenolate-O and alk-
oxy-O of the complementary dimer, the two O–O distances
being respectively 2.802 Å and 2.866 Å in the methoxy com-
pound 1. This pair of noncovalent interactions is further
reinforced by a third H-bond from the coordinated meth-
anol of the complementary square-planar copper (2.686 Å).
Another lattice methanol is H-bonded to the square-planar
copper’s imine-N (2.720 Å). This structural motif resembles
C(9)–N(2)
C(9)–N(3)
1.349(2)
Its 3-ethoxy homologue is very similarly structured (Fig- a precursor or transition state for a penetrative dimerisation
ure 4).
These alkoxy-Schiff base dinuclear chelates display an
of the type recently reported by Ueng et al.[20]
There are no significant structural differences between
interesting framework of hydrogen-bond interactions in the complexes 1 and 2, except for the MeOH molecule coordi-
solid state. Figure 5 indicates how the two dinuclear units nated axially to Cu(2), which in complex 2 is a little more
are stacked so as to entail a centre of inversion.
distant (2.416 vs. 2.546 Å, respectively).
Figure 4. ORTEP representation of the molecular structure of the ethoxy-substituted complex 2 (thermal ellipsoids are shown at the 50%
level).
Eur. J. Inorg. Chem. 2008, 2530–2536
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2533

A. W. Addison et al.
FULL PAPER
Figure 5. Stick rendering (inverse stereoview) of the stacked pair of dimers of 1.
Magnetic Properties
means that the exchange is dx2–y2 – dx2–y2 in nature, leading
to antiferromagnetic coupling, with the rather flat Cu–N–
N–Cu bridges providing an efficient σ pathway for ex-
change. Other azine-bridged dicopper systems with roughly
parallel copper coordination planes also exhibit moderate
to large antiferromagnetic coupling.[10–11,22,23] Indeed,
Thompson et al.[24] have elucidated the way in which the
coupling crosses over (i.e., –2J = 0) at an interplane twist
angle of about 85°. The coupling is antiferromagnetic at
lower twist angles, –2J approaching 225 cm–1 when the co-
ordination planes are parallel (interplane angle 0°). In the
present instances, the CuNNCu torsion angles for the meth-
oxy- and ethoxy-substituted compounds are respectively
4.5° (1) and 8.5° (2).
The magnetic behavior of polycrystalline samples of 1
and 2 in the temperature range 2–300 K in a field of 1 T is
shown in Figure 6. The values of χMT decrease from
0.72 cm3 Kmol–1 at ambient temperature to less than
0.01 cm3 Kmol–1 by 30 K, evidencing substantial antiferro-
magnetic coupling.
The EPR spectra, lacking any fine structure and of low
intensity in both the solid state and solution, are not highly
informative; the methoxy compound exhibits a broad reso-
nance (Hpp ca. 400 G) centred around g = 2.11 and a weak
half-field (∆MS = Ϯ2) resonance. Both compounds display
a trace of ligand-based free radical at g = 2.002.
Conclusions
Figure 6. Plots of χT vs. T for the methoxy (o) and ethoxy com-
pounds (᭡).
2:1 alkoxysalicylaldehyde thiocarbohydrazones form di-
nuclear copper(II) structures under circumstances in which
a second hydrazine nitrogen is kept protonated. The flatness
of the Cu–azine–Cu moiety leads to substantial antiferro-
magnetic coupling. Hydrogen-bond-mediated dimerisation
of the dinuclear molecules is effected in an inversion-sym-
metric modality resembling a pair of plates linked by com-
plementary pin-and-grommet structures.
A standard Bleaney–Bowers model[21] for the coupling of
the two neighbouring spins
H = –2J·S1S2
was used to obtain fits of the data, approximating for the
two copper environments by a single g value. For the meth-
oxy compound with g = 2.17(1), –2J = 189(1) cm–1, ρ =
0.006(1), R2 = 1.4ϫ10–4; for its ethoxy analogue, g =
2.10(1), –2J = 167(1) cm–1, ρ = 0.003(1), R2 = 1.1ϫ10–4 It
is quite unlikely that any water or alcohol H-bond-mediated
interdimer interaction (orthogonal to the magnetic orbitals)
would be of significance vs. these intradimer couplings. The
sign and magnitude of the coupling seem appropriate to
the structural features. The essentially coplanar relationship
Experimental Section
General: All reagents, including 3-methoxysalicylaldehyde (o-vanil-
lin) were used as received from Aldrich Chemical Co. The 1,5-bis(2-
alkoxybenzaldehyde) thiocarbohydrazones were prepared by a
slight modification of the reported procedure.[25] Elemental analy-
between the two coppers’ primary coordination cores ses were from Robertson Microlit, Madison NJ. Fast-atom bom-
2534 Eur. J. Inorg. Chem. 2008, 2530–2536
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

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.
[1] D. D. Awschalom, D. P. DiVincenzo, J. F. Smyth, Science 1992,
258, 414 –417.
[2] S. Gider, D. D. Awschalom, T. Douglas, S. Mann, M. Char-
pala, Science 1995, 95, 77–80.
[3] G. Aromi, E. K. Brechin, Struct. Bonding (Berlin) 2006, 1–67.
[4] R. Sessoli, D. Gatteschi, Angew. Chem. Int. Ed. 2003, 42, 268–
297.
[5] M. Ruben, E. Breuning, J.-M. Lehn, V. Ksenofontov, F. Renz,
P. G ütlich, G. B. M. Vaughan, Chem. Eur. J. 2003, 9, 4422–
4429.
[6] a) A. Ardizzoia, M. A. Angarconi, G. LaMonica, F. Cariati, S.
Cenini, M. Moret, N. Masciocchi, Inorg. Chem. 1991, 30,
4347–4353; b) S. Parsons, J. M. Rawson, D. Reed, R. E. P. Win-
penny, J. Chem. Soc., Dalton Trans. 1995, 163–175.
[7] H. Gang, G. Dong, D. Chun-Ying, M. Hong, M. Qing-jin,
New J. Chem. 2002, 26, 1371–1377.
[8] M. Akbar Ali, P. V. Bernhardt, C. Lee Kiem, A. H. Mirza,
Aust. J. Chem. 2004, 57, 409–413.
[9] H. Cheng, D. Chun-ying, F. Chen-jie, L. Yong-jiang, M. Qing-
jin, J. Chem. Soc., Dalton Trans. 2000, 1207–1212.
[10] a) B. Moubaraki, K. S. Murray, J. D. Ranford, X. Wang, Y.
Xu, Chem. Commun. 1998, 353–354; b) B. Moubaraki, K. S.
Murray, J. D. Ranford, J. J. Vittal, X. Wang, Y. Xu, J. Chem.
Soc., Dalton Trans. 1999, 3573–3578.
[11] D. Dragancea, V. B. Arion, S. Shova, E. Rentschler, N. V. Ger-
beleu, Angew. Chem. Int. Ed. 2005, 44, 7938–7942.
[12] H. Zhou, D. Li, J. Bu, F. Jin, Y. Zhu, J. Zhang, J. Wu, Y. Tian,
S. Chantrapromma, H.-k. Fun, Huaxue Shijie 2006, 47, 94–98.
[13] A. W. Addison, T. N. Rao, J. Reedijk, J. van Rijn, G. C. Ver-
schoor, J. Chem. Soc., Dalton Trans. 1984, 1349–1356.
[14] a) K. Nakamoto, Infrared and Raman Spectra of Inorganic and
Coordination Compounds, 4th ed., Wiley-Interscience, New
York, 1986, pp. 232–233; b) M. Calligaris, L. Randaccio, in
Comprehensive Coordination Chemistry (Eds.: G. Wilkinson,
R. D. Gillard, J. A. McCleverty), Pergamon Press, Oxford,
U.K., 1987, vol. 2, pp. 719, 724.
[15] M. J. M. Campbell, Coord. Chem. Rev. 1975, 15, 279–319.
[16] V. V. Pavlishchuk, S. V. Kolotilov, A. W. Addison, R. J. Butcher,
E. Sinn, J. Chem. Soc., Dalton Trans. 2000, 335–341.
[17] C. Bustos, O. Burckhardt, R. Schrebler, D. Carillo, A. M. Arif,
A. H. Cowley, C. M. Nunn, Inorg. Chem. 1990, 29, 3996–4001.
[18] S. C. Zabin, C. R. Jejurkar, Asian J. Chem. 1995, 7, 542–550.
[19] a) M. Parra-Hake, M. L. Larter, P. Gantzel, G. Aguirre, F. Or-
tega, R. Somanathan, P. J. Walsh, Inorg. Chem. 2000, 39, 5400–
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
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjic.org
2535

A. W. Addison et al.
FULL PAPER
5403; b) Y. Li, J. Lu, X. B. Cui, J. Q. Xu, Y. H. Sun, L. Y. Pan,
H. Y. Bie, X. Zhang, Pol. J. Chem. 2004, 78, 779–787; the ad-
ditional non-copper(II) cases in the CCDC are ELOHUI,
GUHZAK, LAPTIF, LOPNIN, NAJRUL, NESFEW,
ODOLIC, PRHBOS, SAFGOV, VADZAC, VIXKAO,
XOMROG & YIQBOP.
[22] A. Bacchi, A. Bonini, M. Carcelli, F. Ferraro, E. Leporati, C.
Pelizzi, G. Pelizzi, J. Chem. Soc., Dalton Trans. 1996, 2699–
2704.
[23] Z. Xu, L. K. Thompson, D. O. Miller, Inorg. Chem. 1997, 36,
3985–3995.
[24] L. K. Thompson, Z. Xu, A. E. Goeta, J. A. K. Howard, H. J.
Clase, D. O. Miller, Inorg. Chem. 1998, 37, 3217–3229.
[25] R. Yanping, D. Rongbin, W. Liufang, W. Jigui, Synth. Com-
mun. 1999, 29, 613–617.
[26] R. L. Dutta, A. Syamal, Elements of Magnetochemistry, Affili-
ated East-West Press Pty. Ltd., Delhi, 1993, 7–11.
[27] E. J. Billo in Excel for Scientists & Engineers, Wiley-Intersci-
ence, Hoboken, NJ, 2007.
[20]
S.-H. Ueng, S.-Y. Hsueh, C.-C. Lai, Y.-H. Liu, S.-M. Peng, S.-
H. Chiu, Chem. Commun. 2008, 817–819.
[21] B. Bleaney, K. D. Bowers, Proc. R. Soc. London, Ser. A 1952,
214, 451–465; the susceptibility per mol of dimer is χm
=
(1 – ρ)g2Nβ2
ρg2Nβ2
2kT
+
+ 2TIP; ρ is the fraction of coppers
kT[3, exp(–2J/kT)
]
present as paramagnetic impurity; the TIP was constrained to
60ϫ10–6 cgsu per Cu; Nβ2/k = 0.3751; the χm values were
based on the microanalytical data for the magnetochemistry
samples; the measure of the deviation of the fit is R2(χT) =
Σ(χTobsd. – χTcalcd.)2/Σ(χTobsd.)2.
[28] G. M. Sheldrick, SHELXTL: Structure Determination Soft-
ware Suite, version 6.14, Bruker AXS, Madison, WI, USA,
2003.
Received: November 6, 2007
Published Online: April 21, 2008
2536
www.eurjic.org
© 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2008, 2530–2536