Copper complexes with N-aminotriazolethione azomethines: Structures and magnetochemical properties

Article abstract of DOI:10.1134/S107032841003005X

Azomethine derivatives of 4-amino-1,2,4-triazole-3-thiones (H₂L) and their metal complexes were obtained. The stabilities of the ligand conformers were calculated using quantum-chemical techniques. Ab initio (B3LYP/LANL2DZ) calculations of the complexes in the lower singlet and triplet states were performed with full geometry optimization. The structures and magnetochemical properties of the chelate complexes obtained were examined over a wide temperature range.

Full text of DOI:10.1134/S107032841003005X

ISSN 1070ꢀ3284, Russian Journal of Coordination Chemistry, 2010, Vol. 36, No. 3, pp. 189–197. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © I.S. Vasil’chenko, A.S. Burlov, T.E. Shestakova, V.N. Ikorskii, T.A. Kuz’menko, V.G. Vlasenko, K.V. Bozhenko, L.N. Divaeva, A.S. Morkovnik,
A.S. Bogomyakov, D.A. Garnovskii, A.I. Uraev, I.V. Pirog, G.S. Borodkin, A.N. Utenyshev, I.G. Borodkina, O.A. Karpov, A.A. Khrulev, I.E. Uflyand, A.D. Garnovskii,
S.M. Aldoshin, V.I. Minkin, 2010, published in Koordinatsionnaya Khimiya, 2010, Vol. 36, No. 3, pp. 191–199.
Copper Complexes with NꢀAminotriazolethione Azomethines:
Structures and Magnetochemical Properties
,
, †
I. S. Vasil’chenkoa *, A. S. Burlova, b, T. E. Shestakovac, V. N. Ikorskiid , T. A. Kuz’menkoa,
V. G. Vlasenkoe, K. V. Bozhenko f, L. N. Divaevaa, A. S. Morkovnika, A. S. Bogomyakovd,
D. A. Garnovskiia, b, A. I. Uraeva, b, I. V. Piroge, G. S. Borodkina, A. N. Utenyshev f,
I. G. Borodkinaa, O. A. Karpova, A. A. Khrulev f, I. E. Uflyandc, A. D. Garnovskiia, b,
S. M. Aldoshin f, and V. I. Minkina, b
a Research Institute of Physical and Organic Chemistry, Southern Federal University, RostovꢀonꢀDon, Russia
b Southern Scientific Center, Russian Academy of Sciences, RostovꢀonꢀDon, Russia
c Pedagogical Institute, Southern Federal University, RostovꢀonꢀDon, Russia
d International Tomography Center, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia
e Research Institute of Physics, Southern Federal University, RostovꢀonꢀDon, Russia
f Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow oblast, Russia
*Eꢀmail: vas@ipoc.rsu.ru
Received April 14, 2009
Abstract—Azomethine derivatives of 4ꢀaminoꢀ1,2,4ꢀtriazoleꢀ3ꢀthiones (H2L) and their metal complexes
were obtained. The stabilities of the ligand conformers were calculated using quantumꢀchemical techniques.
Ab initio (B3LYP/LANL2DZ) calculations of the complexes in the lower singlet and triplet states were perꢀ
formed with full geometry optimization. The structures and magnetochemical properties of the chelate comꢀ
plexes obtained were examined over a wide temperature range.
DOI: 10.1134/S107032841003005X
Stabilization of various tautomers of ligand systems (NHR, OH, or SH) at the C atom adjacent to the
coordinated to a metal atom is among fundamental amino group (e.g., compounds I). Tautomeric equilibꢀ
problems of modern coordination chemistry [1–3]. rium in such systems can be represented by scheme (1).
Convenient models for the study of such processes are For X = O and S, the equilibrium is usually shifted
azomethine derivatives of Nꢀamines of fiveꢀmembered toward keto (thione) form Ia, while for X = NR (R = H,
nitrogen heterocycles containing a functional group Alk, or Ar), amino form Ib is dominant [4].
R1
A N
R1
A N
H
H
(1)
R2
X
R2
X
N
N
N
N
H
R
R
(Ib)
( )
Ia
X = NR3, O, S; R = Ar,
o
ꢀHNTsPh, oꢀHOAr, oꢀHO(HS)Het;
A = C, R1, R2 = C6H4ꢀcyclo; A = N, R1 is absent, R2 = H, Me, Et;
R3 = H, Alk, Ac.
Current investigations of the coordination mines of 1ꢀaminobenzoimidazolineꢀ2ꢀthione [5]
activity of such imino derivatives are restricted to and, for some metals, 4ꢀaminoꢀ1,2,4ꢀtriazolineꢀ2ꢀ
the study of the structures and properties of aldiꢀ thione [6].
†
Deceased.
189

190
VASIL’CHENKO et al.
N
N
R
N
N
Cu
S
S
X
Cu
N
N
X
R
N
XH
(A)
N
H2N
S
N
N
N
S
R
N
N
H
R
N
(2)
N
H
(II)
R
S
III: X = NTs, R = H (a);
X = NTs, R =Me ( );
X = O, R = H ( );
X = O, R = Me ( ).
N
S
X
X
N
N
N
b
N
Cu
Cu
N
c
N
N
d
R
(B)
IV: X = NTs, R = H (a);
X = NTs, R =Me ( );
X = O, R = H ( );
X = O, R = Me ( ).
b
c
d
We obtained 4ꢀaminoꢀ1,2,4ꢀtriazoleꢀ5(4H)ꢀ
thiones (II), azomethines (III), and their metal comꢀ zylidene)aminoꢀ1,2,4ꢀtriazolineꢀ3ꢀthione (IIIb).
Synthesis
of
5ꢀmethylꢀ4ꢀ(2'ꢀtosylaminobenꢀ
A
plexes (IV), studied their structures and properties, solution of 2ꢀtosylaminobenzaldehyde (2.75 g,
and performed ab initio calculations of the total enerꢀ 0.01 mol) in ethanol and a catalytic amount of piperiꢀ
gies of the singletꢀ and tripletꢀexcited chelate comꢀ dine (one to two drops) were added to a solution of 4ꢀ
plexes in the B3LYP/6ꢀ31G** (for the ligands) and aminoꢀ5ꢀmethylꢀ1,2,4ꢀtriazolineꢀ3ꢀthione (1.30 g,
B3LYP/LANL2DZ approximations.
0.01 mol) in ethanol. The reaction mixture was
refluxed for an hour. On cooling, the white precipitate
that formed was recrystallized from chloroform. The
EXPERIMENTAL
yield of compound IIIb was 2.9 g (74.3%), Tm = 218–
Synthesis of 4ꢀ(2'ꢀtosylaminobenzylidene)aminoꢀ
1,2,4ꢀtriazolineꢀ3ꢀthione (IIIa). A solution of 2ꢀtosyꢀ
laminobenzaldehyde (2.75 g) in glacial acetic acid
(5 ml) was added to a solution of 4ꢀaminoꢀ1,2,4ꢀtriaꢀ
zolineꢀ3ꢀthione (1.16 g, 0.01 mol) in glacial acetic
acid (10 ml). The reaction mixture was refluxed for
4 h. On cooling, the white precipitate that formed was
recrystallized from chloroform. The yield of comꢀ
220°C.
IR (
3084 (
1H NMR (DMSOꢀd6,
ν
, cm–1): 919 (
(NHtriaz)), 3157 (
ν
(C=S)), 1608 (
(NHTs)).
, ppm): 2.38 (s, 3H,
ν(C=Nazomet)),
δ
δ
δ
ArCH3), 2.42 (s, 3H, TriazCH3), 7.2–7.8 (m, 8H,
Har), 10.15 (s, 1H, NHtriaz), 10.20 (s, 1H, HC=N),
13.63 (s, 1H, ArSO2NH).
For C17H17N5O2S2
pound IIIa was 2.8 g (75.5%),
IR ( (C=S)), 1602 (
, cm–1): 920 (
3082 ( (NHtriaz)), 3153 ( (NHTs)).
1H NMR (DMSOꢀd6,
, ppm): 2.38 (s, 3H,
Tm = 232°C.
anal. calcd., %: C, 52.70;
Found, %: C, 52.67;
H, 4.42;
H, 4.45;
N, 18.07.
N, 18.01.
ν
ν
ν
(C=Nazomet)),
δ
δ
δ
ArCH3), 7.2–7.8 (m, 8H, Har), 8.80 (s, 1H, CHtriaz),
9.80 (s, 1H, HC=N), 10.15 (s, 1H, NHtriaz), 13.60 (s,
1H, ArSO2NH).
Synthesis of 4ꢀ(2'ꢀhydroxybenzylidene)aminoꢀ
1,2,4ꢀtriazolineꢀ3ꢀthione (IIIc). Salicylaldehyde (1.2 g,
0.01 mol) was added to a solution of 4ꢀaminoꢀ1,2,4ꢀ
triazolineꢀ3ꢀthione (1.16 g, 0.01 mol) in glacial acetic
acid (5 ml). The reaction mixture was refluxed for an
hour. On cooling, the white precipitate that formed
was recrystallized from butanol. The yield of comꢀ
For C16H15N5O2S2
anal. calcd., %: C, 51.46;
Found, %: C, 51.49;
H, 4.05;
H, 4.10;
N, 18.75.
N, 18.77.
pound IIIc was 1.66 g (75.6%), Tm = 263–265°C.
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COPPER COMPLEXES WITH NꢀAMINOTRIAZOLETHIONE AZOMETHINES
191
IR (
3083 (
1H NMR (DMSOꢀd6,
Har), 8.82 (s, 1H, Htriaz), 9.65 (s, 1H, HC=N), 10.50
(s, 1H, NH), 13.80 (s, 1H, OH).
ν
δ
, cm–1): 917 (
(NHtriaz)), 3159 (
ν
(C=S)), 1612 (
(OH)).
, ppm): 6.8–7.7 (m, 4H,
ν
(C=Nazomet)),
CuKꢀedge Xꢀray absorption spectra of metal comꢀ
δ
plexes were recorded in the absorption detection mode
on an EXAFS spectrometer at the Siberian synchroꢀ
tron center (Novosibirsk). The energy of an electron
beam employed as a synchrotron Xꢀray source was
2 GeV at an average current of 80 mA. For Xꢀray
monochromatization, a twoꢀcrystal Si(111) monoꢀ
chromator was used. The intensities of the incident
and transmitted Xꢀrays were measured in argonꢀfilled
ion chambers. Background subtraction, normalizaꢀ
δ
For C9H8N4OS
anal. calcd., %: C, 49.08;
Found, %: C, 49.11;
H, 3.66;
H, 3.70;
N, 25.44.
N, 25.49.
tion for a
Kꢀedge jump, and removal of the atomic
absorption μ0 were performed according to standard
procedures. The EXAFS spectra were Fourierꢀtransꢀ
formed (EXAFS is an abbreviation for extended Xꢀray
absorption fine structure) for each sample in a photoꢀ
electron wave vector range from 2.5 to 13 Å–1 with the
weight function k2. The exact parameters of the local
environment of the Cu atom were determined by
approximating the calculated EXAFS spectra to the
experimental one via variation of the parameters of the
corresponding coordination spheres with the IFFEFIT
program.
Synthesis of 4ꢀ(2'ꢀhydroxybenzylidene)aminoꢀ5ꢀ
methylꢀ1,2,4ꢀtriazolineꢀ3ꢀthione (IIId). Salicylaldeꢀ
hyde (1.22 g, 0.01 mol) was added to a solution of 4ꢀ
aminoꢀ5ꢀmethylꢀ1,2,4ꢀtriazolineꢀ3ꢀthione (1.30 g,
0.01 mol) in glacial acetic acid (10 ml). The reaction
mixture was refluxed for an hour. On cooling, the
white precipitate that formed was recrystallized from
anhydrous ethanol. The yield of compound IIId was
0.8 g (38%),
IR (
, cm–1): 913 (
3072 ( (NHtriaz)), 3126 (
1H NMR (DMSOꢀd6,
T
m = 210°C.
(C=S)), 1598 (
(OH)).
, ppm): 2.40 (s, 3H, CH3),
ν
δ
ν
ν(C=Nazomet)),
δ
δ
6.8–7.9 (m, 4H, Har), 10.15 (s, 1H, HC=N), 10.20
(s, 1H, NH), 13.50 (s, 1H, OH).
RESULTS AND DISCUSSION
Structures III (R = H, Me, and Et; X = NMs) were
determined using quantumꢀchemical calculations.
These ligands contain a single asymmetric atom (tetꢀ
rahedral N atom of the mesylamino group) and,
according to the PM3ꢀcalculated structure for R = H,
can exist as many (over 10) conformers. In the latter,
both the rings are usually not coplanar, their planes
For C10H10N4OS
anal. calcd., %: C, 51.27;
Found, %: C, 51.19;
H, 4.30;
H, 4.26;
N, 23.91.
N, 23.86.
Complexes IVa–IVd were synthesized according to
making a large angle. However, in conformer III'
,
the following standard procedure. A hot solution of
copper acetate (2 mmol) in methanol (10 ml) was
added to a boiling solution of an appropriate ligand
(2 mmol) in methanol (20 ml). The reaction mixture
was refluxed for 5 min. On cooling, the precipitate that
formed was filtered off, washed with hot methanol,
and dried in a vacuum desiccator. The yields were 40–
which is most stable and seems to correspond to the
global minimum, both rings and the atoms of the aldiꢀ
mine fragment are virtually coplanar, while the mesyl
group is out of plane (data from B3LYP/6ꢀ31G** calꢀ
culations) (Fig. 1). The conformer has a relatively low
dipole moment (μcalc = 3.1 D) and contain a fairly
strong endocyclic H bond between the NH group as a
donor and the aldimine N atom as an acceptor (N–N,
65%, dark green solids, Tm > 300°C.
Elemental analysis of the ligand systems and the
complexes for C, H, and N was performed on a Carlo
Erba Instruments TCM 480 instrument at the
Microanalysis Laboratory of the Research Institute of
Physical and Organic Chemistry of the Southern Fedꢀ
eral University.
IR spectra of the solidꢀstate ligands and complexes
were recorded on a Varian EXCALIBUR 3100 FTꢀIR
spectrometer in the 400–4000 cm–1 range.
1H NMR spectra of the ligands were recorded on a
UNITYꢀ300 instrument (Varian) in DMSOꢀd6.
2.71 Å;
N⋅⋅⋅H, 1.87 Å; H⋅⋅⋅N bond order 0.12). This
conformer has an unfavorable structure for tridentate
coordination: the thione fragment is distant from the
hydrogen ring because of the rotation of the triazole
ring about the exocyclic N–N bond through an angle
of ~180
relative to this bond. A structurally similar lowestꢀ
energy conformer was discovered in the study of the
°, which corresponds to the Z configuration
Z
conformations of ligands III (R = H; Y = NMs) by
molecular mechanics (MM2).
At the same time, the conformational system corꢀ
Magnetochemical measurements were carried out responding to compound III (R = H; Y = NMs) also
on a MPMSꢀ5S Quantum Design SQUID magneꢀ includes an conformer relative to the N–N bond
E
tometer (2–300 K, magnetic field strength 5 kOe). with the thione group oriented toward the chelated
The temperature dependence of the effective magnetic hydrogen. This conformer is responsible for potential
moment was calculated by the formula μeff
where is the molar paramagnetic susceptibility corꢀ energy is higher by ~3 kcal/mol. Four constituent
rected for the diamagnetic contribution. atoms in the potential tridentate coordination unit
(T) = 8χT,
tridentate coordination of the ligand and its total
χ
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 36
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192
VASIL’CHENKO et al.
(а)
(b)
N
H
N
H
N
N
1.53
1.67
C
1.58
1.66
1.00
1.40
C
C
S
1.01
1.40
1.04
1.73
H
H
S
N
N
1.01
1.38
N
N
0.10
1.87
C
1.51
1.29
H
0.10
1.86
H
1.51
1.30
H
O
H
C
0.78
1.02
1.12
1.46
1.14
1.45
1.31
1.43
C
C
0.77
1.03
H
1.31
1.43
0.94
1.40
O
H
0.98
1.40
N
H
H
H
S
N
S
C
C
C
C
O
C
C
C
H
C
H
O
C
C
H
H
H
H
C
H
C
H
H
Fig. 1. B3LYP/6ꢀ31G**ꢀcalculated structure III (R = H; X = NMs) in (a) the lowestꢀenergy
formation relative to the N(4)ꢀN(1') bond. For selected bonds, the bond order (upper number) and the length (
are given.
Z
conformation and (b) the
E
conꢀ
A, lower number)
(the NH group, the aldimine N atom, and the S atom) 6.3 kcal/mol). In both the conformers, the triazole
appreciably deviate in the conformer from the ring makes a substantially larger angle with the rest of
meanꢀsquare plane (on average, by ~0.5 Å). However, the ꢀsystem, the angle increase being equal for the
to make the configuration completely planar requires methyl and ethyl derivatives. As the result, the torsion
only ~0.5 kcal/mol. Thus, the overall energy required angle C(3)–N(4)–N(1')–C(2'), which is and 19 in
to transform the dominant conformer into a planar the and conformers, respectively, of the 3ꢀunsubꢀ
configuration is only ~3.5 kcal/mol (in the absence of stituted compound, increases to ~12 and ~44 . This
solvation). Obviously, a lower energy is required in structural effect is due to the electrostatic repulsion of
polar solvents because the conformer, according to the aldimine H atom from the similarly charged H(3)
the calculated dipole moments μcalc (Table 1), is subꢀ atom or from the methyl (methylene) H atoms and
stantially polar than the conformer and should be makes a major contribution to the barrier to rotation
E
π
4°
°
Z
Z
E
°
°
E
Z
stabilized by a highꢀpolarity solvent.
about the N–N bond.
Therefore, compounds III do not have substantial
spatial or electronic factors precluding their tridentate
coordination and hence they can form, e.g., binuclear
metal complexes.
It follows from the IR and 1H NMR spectra, aldiꢀ
mines III in both solution and the solid state exist as an
imine phenol (for the azomethine fragment) and triaꢀ
zoline thione tautomer (for the heterocyclic part).
This is evident from the absorption bands at 900–1100
(C=S stretches) and 3200–3400 cm–1 (N–Htriaz
stretches) in the IR spectra and from the signals for the
XH and N–Htriaz protons in the 1H NMR spectra.
Analogous pairs of conformers were found for
methyl and ethyl derivatives of mesylꢀcontaining
ligands (III: R = Me and Et). In this case too, the
Z
conformer is thermodynamically more stable. In all
six B3LYP/6ꢀ31G**ꢀcalculated structures, the order
of the exocyclic N–N bond is nearly unity, which sugꢀ
gests the absence of noticeable conjugation between
the triazole ring and the aldimine fragment and the
influence of this factor on the barriers to rotation
about this axis.
Replacement of the hydrogen atom in position 3 by
a methyl or ethyl group results in additional considerꢀ
An analysis of the IR spectra of the metal comꢀ
plexes revealed that the reactions of azomethines III
with cupric acetate result in deprotonation of both
parts of the ligand system (the XH group and the triaꢀ
able destabilization of the
E conformers compared
to the Z ones. In energy terms, this destabilization is
total
E–Z
virtually equal for both substituents (ΔE
~
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COPPER COMPLEXES WITH NꢀAMINOTRIAZOLETHIONE AZOMETHINES
193
Table 1. B3LYP/6ꢀ31G**ꢀcalculated data for the conformers of complexes III (X = NMs; R = H, Me, and Et) and their enanꢀ
tiomers
Gibbs energy of the
Torsion angles in the conformer
Gibbs energy of conformer vs. that
Conformer
of complex III
R
the conformer
,
of the most stable
μcalcd, D
C(2)'–N–N– Me–SO2–NH– S–N–C(4)'–
G298
,
au
conformer
(Δ
G298),
C(5), deg
C(4)', deg
C(3)', deg
kcal/mol
III'
H
–1608.021275
–1608.021275
0
–6.3
5.8
62.0
–62.7
165.9
–165.4
68.4
–156.0
157.4
3.1
3.2
5.6
5.6
5.9
2.6
2.6
2.1
1.0
4.4
2.2
5.9
2.0
6.0
6.0
III' enantiomer
H
0
III''
–1608.01618739
–1608.016195
3.2
3.2
3.9
4.6
4.6
4.6
9.0
10.6
0
–165.0
165.6
0.3
147.0
III'' enantiomer
H
H
H
H
–147.2
–123.9
–83.6
83.9
III'''
–1608.0149888
–1608.0139821
–1608.0139723
–1608.01397234
–1608.00670204
–1608.00443033
III''''
–9.6
145.7
–145.7
–168.9
–142.3
16
III'''' enantiomer
9.4
III'''''
III''''''
III'''''''
III'
–44.5
–41.4
–9.5
–106.8
87.7
H
–92.5
–151.4
152.5
Me –1647.327098
Me –1647.3167186
Et –1686.6150072
Et –1686.6073577
–17.3
–147.4
–17.0
–145.9
146.5
59.1
III''
6.5
0
159.5
59.8
III'
–152.8
155.3
III''
4.8
4.8
155.6
–158.0
III'' enantiomer Et –1686.6073562
–153.5
zole fragment). Based on these and elemental analysis sists of two S atoms and three light atoms (N/O)
data, we concluded that the complexes obtained can
be formulated as Cu2L2 (where H2L are aldimines III).
However, it can be seen in (2) that binuclear moleꢀ
cules can form in two ways, the bridging atoms being
(Fig. 2, Table 2) and can be represented as N2OS2
Therefore, complex IVb exists as structure with
bridging S atoms, in which a tosyl O atom is also coorꢀ
dinated to copper. The third main MFT peak at
.
A
r
=
the S atoms of the triazole substituent (structure
the X atoms of the aldehyde fragment ( ).
A) or
2.87–3.07 Å was tested for the presence of coordinaꢀ
B
In [7], we have demonstrated that the N atom of
the tosylamino group cannot serve as a bridging atom;
Table 2. Structural data obtained from the multisphere fit of
EXAFS data*
i.e., complexes IV (X = NTs) exist as structure
A.
Structures IVb and IVd were determined by EXAFS
Comꢀ
N
r
, Å
σ
2, Å2
Atom
Q, %
spectroscopy. The Fourier transform modules of the
plex
EXAFS functions of the CuK edge for these complexes
are shown in Fig. 2. The structural parameters of the
nearest atomic environment of the copper ion in comꢀ
plexes IVb and IVd are given in Table 2.
In complex IVd, the first coordination sphere of the
copper atoms is made up of three N/O atoms of the
ligands at a distance of 1.93–1.97 Å and a S atom at a
distance of 2.28–2.29 Å. Based on the EXAFS data,
the coordination sphere of the central atom in comꢀ
plex IVd can be represented as NO2S and the complex
IVb
1
2
2
1
1
2
1
1
1.92
1.94
2.28
3.07
1.92
1.99
2.28
2.87
0.0033
0.0037
0.0064
0.065
N/O
N/O
S
13.4
Cu
IVd
0.0045
0.0041
0.0041
0.069
N/O
N/O
S
6.3
Cu
exists as structure
nol type. According to the EXAFS data for complex
B with bridging O atoms of the pheꢀ
2
* r is the interatomic distance, N is the coordination number, σ is
the Debye–Waller factor, and Q is the mismatch function.
IVb, the coordination sphere of the copper atom conꢀ
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VASIL’CHENKO et al.
Cu–S
Cu–Cu
Cu–N/O
2.0
1.5
1.0
0.5
2
1
0
2
4
6
8
r
,
Å
Fig. 2. Fourier transform modules of the EXAFS functions of the Cu
K
edge for (
1
)
IVb and (
2
)
IVd. Experimental MFTs are indiꢀ
cated with solid lines; calculated MFTs for the first coordination sphere are indicated with circles.
tion spheres with metal ions. Variation of the integraꢀ tems and the singletꢀtriplet splitting energies for their
tion parameters in the Fourier transform of the funcꢀ lower triplet and singlet states are also tabulated. Hereꢀ
χ
tion convincingly proved that this peak is due to the after, we will understand under triplet and singlet states
coordination sphere of copper ions. The quantitative these lower states.
characteristics of this coordination sphere are given in
The presence of the S atom in the central fragment
Table 2. The calculated copper–copper distance is
makes a planar triplet structure angular; this distincꢀ
typical of copper dimers (Cu–Cu, 2.90–3.1 Å [8]).
tive feature is fundamental for the influence of the sulꢀ
To study the dependence of ferromagnetic ordering fur atom on the structure of the complex.
in azomethine chelate complexes on structural facꢀ
To reveal the most significant geometrical parameꢀ
tors, we performed quantumꢀchemical calculations of
ters and study them in more detail, let us consider the
two series of isomers (A and B) with the GAUSSIANꢀ
spin density (SD) distributions in the complexes of
series and . The spin densities for the groundꢀstate
1
A
B
03 program in the B3LYP/LANL2DZ approximaꢀ
tion with full geometry optimization for the groundꢀ
state triplet and lower singlet molecules of each dimer.
In addition, when calculating the “broken symmetry”
energy in the approach [9] required to calculate
exchange constants, we separately optimized the
triplet complexes under discussion are given in
Table 4.
For all the calculated triplet states of the comꢀ
plexes, the SD is essentially distributed only over four
atoms of the central fragment of each complex and
over the nearest adjacent four atoms. The highest SD
2
dimer geometry in the singlet state. The calculated
accumulates on copper atoms (~0.4–0.5 e, Table 4).
In complexes IV, types of R are different in the termiꢀ
nal rather than central fragments; that is why replaceꢀ
ment of one type of R by another should have a weaker
effect on SD of the copper atoms in the central fragꢀ
ment. Indeed, it can be seen in Table 4 that the variaꢀ
tion in R produces virtually no effect on the SD distriꢀ
bution over the atoms in the central fragment. From
series have different central fragments: (Cu–S)2 in
series
A and (Cu–O)2 in series B.
In the complexes, their two “moieties” adjacent to
the central fragments have different relative positions
(Fig. 3). The total energies Etot of the calculated sysꢀ
1
License to Use Agreement: Gaussian, Inc., 340 Quinnipiac
Street, Building 40, Wallingford, CT 06492.
2
~1.93 to ~1.98
e (out of the maximum possible 2.0 e
The option opt=loose was used.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 36
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2010

COPPER COMPLEXES WITH NꢀAMINOTRIAZOLETHIONE AZOMETHINES
195
μeff
,
μB
(а) μeff
,
μB
(b)
5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
4
3
2
0
,
50 100 150 200 250 300
, K
0
50 100 150
200 250 300
T, K
T
μeff
2.4
2.2
μB
(c)
2.0
1.8
1.6
1.4
0
50
100 150 200 250 300
T, K
Fig. 3. Temperature dependence of the effective magnetic exchange for complexes (a) IVb, (b) IVc, and (c) IVd
.
for the triplet state) accumulate on four atoms of the the complexes based on paramagnetic metal ions
central fragments and the nearest adjacent four atoms.
Note that each S atom in the complexes studied bears
(Fig. 3).
Hence, complexes IVb and IVd exhibit antiferroꢀ
~0.32–0.33 e, i.e., with a decrease in SD on the copper
atoms, it increases on the nearest other two atoms of
the central fragment and vice versa. Thus, the four
atoms of the central fragment have parallel spins,
which is favorable for magnetic exchange because of
relatively short distances between them.
magnetic spinꢀspin interactions, while dimer IVc is
characterized by ferromagnetic exchange. These
results can be explained by (1) the influence of addiꢀ
tional coordination of the tosylamino O atom by the
copper atom on the characteristics of magnetic
exchange (it should be ferromagnetic in the case of
exchange through sulfur bridges) in dimer IVb and
(2) the formation of various types of the exchange cheꢀ
late ring in salicylaldimine complexes: Cu2O2 for IVd
(structure
To sum up, quantumꢀchemical calculations and
physicochemical studies showed that ꢀtosyꢀ
lamino(hydroxy)aldimines of 4ꢀaminoꢀ1,2,4ꢀtriazꢀ
oleꢀ5ꢀthiones form dimeric copper complexes and
that their magnetochemical properties depend on the
For examination of the magnetic properties of
these complexes, the singletꢀtriplet splitting energy is
most interesting since this quantity numerically equals
the exchange integral (i.e., it is a quantitative characꢀ
teristic of electron exchange interactions). First of all,
note that in all the calculated complexes, the triplet
state is much lower than the singlet state and correꢀ
sponds to their energy ground state, which suggests
possible magnetic ordering in these systems.
B) or Cu2S2 for IVc (structure A).
o
Magnetochemical measurements over a wide temꢀ
perature range showed that spin exchange occurs in all bridging atoms.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 36
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2010

196
VASIL’CHENKO et al.
Table 3. Selected geometrical features, total energies Etot of the ground triplet and lower singlet states, singletꢀtriplet splitting
ˆ2
energy ΔE, “broken symmetry” energy Ebs, eigenvalues of the operator S , and exchange constants J for series A and B
R
Geometry
Etot
,
au
Δ
E,
kcal/mol
13.18
Eнс
,
au
J,
cm–1
Series A
H
S
Angular
–1693.849
–1693.870
–1693.870
ˆ2
T
Angular
–11.8
34.6
7.5
S
= 0.980
CH3
S
Angular
Angular
–1772.480
–1772.502
13.81
13.53
–1772.502
ˆ2
T
S
= 0.977
C2H5
S
Parallel to the plane
Angular
–1851.092
–1851.114
–1851.114
ˆ2
T
S
= 0.979
Series B
H
S
Angular
Angular
–1693.862
–1693.889
17.02
17.23
–1693.891
ˆ2
T
–433.9
–409.8
–399.0
S
= 0.953
CH3
C2H5
S
Angular
Angular
–1772.493
–1772.520
–1772.523
ˆ2
T
S
= 0.955
S
Angular
Angular
–1851.106
–1851.133
–1851.135
ˆ2
T
17.27
S
= 0.955
ACKNOWLEDGMENTS
Table 4. Spin densities of the complexes of series A and B in
the triplet state
This work was supported by the Presidium of the
Russian Academy of Sciences (program “Molecular
design of magnetically active compounds and materiꢀ
als (molecular magnetics)"), the Ministry of Educaꢀ
tion and Science of the Russian Federation (grant
RNP.2.2.1.1/2348), the President of the Russian Fedꢀ
eration (grant NShꢀ363.2008.3), the joint program of
the Ministry of Education and Science of the Russian
Federation (project 2.2.2.3.10010) and the Civilian
Research and Development Foundation (grant Y4ꢀ
C04ꢀ02), the Russian Foundation for Basic Research
(project nos. 07ꢀ03ꢀ00710 and 08ꢀ03ꢀ00223), and the
Southern Federal University grant.
Atom
R = H
R = CH3
Series A
R = C2H5
Cu
S
S
0.408
0.325
0.326
0.152
0.079
0.408
0.152
0.107
0.407
0.339
0.339
0.140
0.080
0.407
0.140
0.080
0.407
0.338
0.338
0.141
0.079
0.407
0.142
0.080
O
N
Cu
O
N
Series B
Cu
O
O
S
Cu
S
0.490
0.122
0.122
0.298
0.490
0.298
0.091
0.091
0.490
0.122
0.122
0.294
0.490
0.294
0.095
0.095
0.490
0.122
0.122
0.293
0.490
0.293
0.095
0.095
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2010