Synthesis and structure of polycrystalline adducts of Co(II) azomethine complexes with redox-active 2,4,6,8-tetrakis-(tert-butyl)phenoxazin-1-one

Article abstract of DOI:10.1134/S1070328416040011

The six-coordinate cobalt complexes, C₅₇H_63.50N_4.50O₄Co (IIa), C₆₀H₆₉N₅O₄Co (IIb), C5₈H₆₇N₃O₈Co (IIc), C₅₆H

Full text of DOI:10.1134/S1070328416040011

ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2016, Vol. 42, No. 4, pp. 252–259. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © E.P. Ivakhnenko, Yu.V. Koshchienko, P.A. Knyazev, V.B. Nalbandyan, K.A. Lyssenko, I.V. Ananyev, A.S. Bogomyakov, V.I. Minkin, 2016, published
in Koordinatsionnaya Khimiya, 2016, Vol. 42, No. 4, pp. 221–229.
Synthesis and Structure of Polycrystalline Adducts of Co(II)
Azomethine Complexes with Redox-Active 2,4,6,8-Tetrakis-
(tert-Butyl)Phenoxazin-1-one
E. P. Ivakhnenkoa, *, Yu. V. Koshchienkoa, P. A. Knyazeva, V. B. Nalbandyanb, K. A. Lyssenkoc,
I. V. Ananyevc, A. S. Bogomyakovd, and V. I. Minkina
aResearch Institute of Physical and Organic Chemistry, Southern Federal University, Rostov-on-Don, Russia
bSouthern Federal University, Rostov-on-Don, Russia
cNesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences, ul. Vavilova 28, Moscow, 119991 Russia
dInternational Tomography Center, Siberian Branch, Russian Academy of Sciences, Novosibirsk, Russia
*e-mail: e.ivakhnenko@ipoc.sfedu.ru
Received July 28, 2015
Abstract—The six-coordinate cobalt complexes, C57H63.50N4.50O4Co (IIa), C60H69N5O4Co (IIb),
C58H67N3O8Co (IIc), C56H61N5O10Co (IId), C56H63N3O6Co (IIe), C58H66N4O6Co (IIf), and
C58H63N7O8Co (IIg), adducts of high-spin tetrahedral Co(II) bis(salicylaldiminates) (C29H24.50N3.50O2Co
(Ia), C32H30N4O2Co (Ib), C30H28N2O6Co (Ic), C28H22N4O8Co (Id), C28H24N2O4Co (Ie), C30H27N3O4Co
(If), and C30H24N6O6Co (Ig)) and redox-active 2,4,6,8-tetrakis(tert-butyl)phenoxazin-1-one (L), were syn-
thesized and studied for structure and magnetic properties. Complexes IIa–IIg have octahedral structure
(CIF files CCDC nos. 1403920 (IIf), 1403922 (IIg)) and exist in the ground low-spin state (ls-CoIII-SQ),
which arises upon intramolecular single-electron redox process in the ligand–metal system. The presence of
substituents of different nature in the azomethine ligands of IIa–IIg does not induce any significant changes
in their magnetic properties.
DOI: 10.1134/S1070328416040011
INTRODUCTION
ligand
six-coordinate
cobalt
complexes,
C57H63.50N4.50O4Co (IIa) and C60H69N5O4Co (IIb),
by the reaction of the redox-active 2,4,6,8-
tetrakis(tert-butyl)phenoxazin-1-one (C28H39NO2,
L) with high-spin tetrahedral Co(II) bis(salicylaldi-
minates) (I) on heating in toluene [13, 14]. This work
deals with the synthesis of new complexes:
C58H67N3O8Co (IIc), C56H61N5O10Co (IId),
C56H63N3O6Co (IIe), C58H66N4O6Co (IIf), and
C58H63N7O8Co (IIg) (Scheme 1), the spatial and
electronic structures of these complexes, and the
effect of substituents in the azomethine moiety of
cobalt complexes on the state and redox isomerism
processes. A new convenient solid-phase synthesis of
complexes II is presented and the magnetic proper-
ties and the EPR spectra of the crystalline powders of
Molecular magnetic materials that exist in the
crystalline state in two or several thermodynamically
stable forms are of considerable interest as molecular
switches with magnetic response and high-capacity
molecular memory. Among the most promising
objects for the design of these materials are coordina-
tion compounds of transition metals containing elec-
tro-active (so-called non-innocent) ligands that can
have nearly degenerate electronic states arising upon
low-barrier thermo- or photo-stimulated electron
transfer between the ligand and metal ion [1–6].
These states (valence tautomers) have different phys-
ical properties [7–10] and, therefore, compounds
and dynamic materials based on them are of consid-
erable interest for diverse applications in technology
[11, 12].
Previously, we demonstrated the possibility of
preparing potentially valence-tautomeric mixed- the resulting adducts are studied.
252

SYNTHESIS AND STRUCTURE OF POLYCRYSTALLINE ADDUCTS
253
R
t-Bu
t-Bu
O
N
N
O
R1
O
N
Co
+
R1
t-Bu
t-Bu
O
R
Ia, b, c, d, e, f, g
L
t-Bu
t-Bu
t-Bu
t-Bu
O
O
t-Bu
R1
t-Bu
R1
N
t-Bu
N
t-Bu
R
R
O
O
3+
2+
Co
Co
O
N
O
N
N
N
O
O
R1
R1
R
R
IIa, b, c, d, e, f, g
II'
hs-CoII-Q
ls-CoIII-SQ
a: R = R1 = H
e: R = H, R1 = OCH3
f: R = OCH3, R1 = H
g: R = NO2, R1 = H
b: R = CH3, R1 = H
c: R = R1 = OCH3
d: R = OCH3, R1= NO 2
Scheme 1.
EXPERIMENTAL
were performed using a Quantum Design MPMSXL-
SQUID magnetometer in the 2–300 K range.
Cobalt bis[2-(phenyliminomethyl)phenolate] Ia
and cobalt bis[2-(p-tolyliminomethyl)phenolate] Ib
were prepared by a reported procedure [15].
The IR spectra of the polycrystalline samples were
recorded on a Varian Excalibur 3100 FRT-IR spec-
trometer. Powder X-ray diffraction analysis was per-
formed on an ARL X’tra powder diffractometer (CuKα
radiation) using a semiconductor detector to eliminate
General procedure for the preparation of complexes
the fluorescent radiation of cobalt. The EPR spectra IIa–IIg. A solution of phenoxazinone L (0.3 mmol) in
were recorded on an EMX Plus 10/12 Bruker X-band benzene (5 mL) was added to a solution of complex I
spectrometer. The hyperfine splitting (HFS) constants (0.3 mmol) in benzene (5 mL), and the resulting solu-
for the EPR spectra were calculated using the Win tion was refluxed for 30 min. The solvent was evapo-
EPR SimFonia Bruker program package and the mag- rated, and the residue was dried in air. The complexes
netic measurements for polycrystalline complexes thus obtained were recrystallized from acetonitrile.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 4 2016

254
IVAKHNENKO et al.
Complex IId (R = OCH3, R1 = NO2): crystals,
brown needles. Yield 68%. mp = 190–191°C.
Table 1. Selected crystallographic data and refinement
details for structures IIf and IIg
Value
Parameter
For C56H61N5O10Co
IIf
IIg
anal. calcd., %: C, 65.74;
Found, %: C, 65.63;
H, 6.01;
H, 6.15;
N, 6.93.
N, 6.93.
Molecular formula
C58H66CoN4O6 C58H63CoN7O8
М
975.59
100
1045.08
100
T, K
Complex IIe (R = H, R1 = OCH3): crystals, brown
needles. Yield 91%. mp= 133–134°C.
Crystal system
Space group
Z
Triclinic
P1
Triclinic
P1
For C56H63N3O6Co
2
2
anal. calcd., %:
Found, %:
C, 72.09;
C, 72.01;
H, 6.81;
H, 6.89;
N, 4.50.
N, 4.58.
a, Å
14.3796(16)
14.7410(16)
14.9120(17)
61.7910(18)
69.3090(19)
68.603(2)
2529.7(5)
12.8556(16)
12.9725(16)
16.013(2)
86.366(2)
83.232(2)
80.839(2)
2615.3(6)
b, Å
Complex IIf (R = OCH3, R1 = H): crystals, brown
needles. Yield 86%. mp = 133–134°C.
c, Å
α, deg
β deg
For C58H66N4O6Co
γ, deg
V, Å3
anal. calcd., %: C, 71.51;
Found, %: C, 71.98;
H, 6.83;
H, 6.90;
N, 5.75.
N, 5.67.
ρ(calcd.), g cm–3
μ, cm–1
1.281
3.95
1.327
3.91
Complex IIg (R = NO2, R1 = H): crystals, brown
needles. Yield 95%. mp = 138–139°C.
F(000)
1037
50
1102
54
2θmax, deg
For C58H63N7O8Co
Number of measured
reflections
32195
24674
anal. calcd., %: C, 66.66;
Found, %: C, 66.70;
H, 6.08;
H, 6.05;
N, 9.38.
N, 9.37.
Number of unique
reflections
14805
10703
656
11348
6278
681
Synthesis of adducts IIa, IIb, and IIg by the solid-
phase reaction of Co(II) bis(salicylaldiminates) with
Number of reflections
with I > 2θ(I)
2,4,6,8-tetra(tert-butyl)phenoxazin-1-one.
Com-
pound L (84 mg, 0.2 mmol) and compound Ia
(0.2 mmol) were placed in agate mortar and thor-
oughly ground with an agate pestle to give a uniform
mixture. Complex IIa was a dark brown crystalline
powder (mp = 139–141°C; yield 98%). Complexes IIb
and IIg were prepared by a similar procedure (mp =
134–136°C and 138–139°C, respectively). The com-
pleteness of the reaction was checked by IR spectros-
copy.
Number of refined
parameters
R1, wR2 (I > 2θ(I))
R1, wR2 (all data)
GOOF
0.0490, 0.1183 0.0514, 0.0993
0.0759, 0.1314 0.1211, 0.1208
1.015
0.914
Δρmax/ρmin, e Å–3
0.937/–0.664 0.574/–0.892
X-ray diffraction study of IIf and IIg was carried out
Complexes IId and IIg were synthesized in DMF. The on a Bruker APEX II Duo diffractometer (MoKα radi-
ation, graphite monochromator, ω-scan mode). The
structures were solved by the direct method and
refined by the least squares method in the anisotropic
crystals of complexes IIf and IIg suitable for X-ray dif-
fraction were prepared by slow evaporation of acetoni-
trile solutions. Complexes IIa and IIb were synthe-
sized by reported procedures [13, 14].
Fh2kl.
approximation on
The hydrogen atoms were
located from the Fourier difference maps and refined
in the isotropic approximation in the riding model.
The structures were solved and refined using the
SHELXTL PLUS program package [16]. Selected
crystallographic data and refinement parameters for
IIf and IIg are summarized in Table 1 and the bond
lengths and angles are in Table 2. Full X-ray diffrac-
tion data for IIf and IIg are available at the Cambridge
Complex IIc (R = R1 = OCH3): crystals, brown
needles. Yield 94%. mp = 165–166°C.
For C58H67N3O8Co
anal. calcd., %:
Found, %:
C, 70.15;
C, 70.08;
H, 6.80;
H, 6.94;
N, 4.23.
N 4.28.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
Vol. 42
No. 4
2016

SYNTHESIS AND STRUCTURE OF POLYCRYSTALLINE ADDUCTS
255
Table 2. Selected bond lengths (Å) and bond angles (deg) in
complexes IIf and IIg
these complexes virtually do not differ from those
found previously for low-spin compounds IIa and IIb
with the phenoxazinone ligand in the semiquinolate
(SQ) form [14]. The Co–O and Co–N bond lengths
of the phenoxazin-1-one moiety in these compounds
are 1.871(2)–1.8920(12) and 1.930(2)–1.9772(14) Å,
respectively, and almost do not differ from the Co–O
and Co–N bond lengths in IIa and IIb (1.873(2)–
1.893(2) and 1.950(3)–1.976(3) Å, respectively). The
Co–O and Co–N bond lengths are somewhat shorter
than those expected in a coordination unit for quinoid
ligands containing oxygen and nitrogen [17]. This
indicates that the Co3+ central ion exists in the low-
spin form. In compounds IIf and IIg, the O(1)–C(1)
bond lengths (1.311(2)–1.320(3) Å) differ only within
the error from the corresponding values in IIa and IIb
(1.314(4)–1.312(4) Å) [14] and are consistent with the
average lengths of these bonds for the ligands existing
in the iminosemiquinone form [18]. The most pro-
nounced differences in the geometry of complexes IIf
and IIg are found for the rotation angle of the aryl sub-
stituent. This angle is 49°–68° in IIf and 75°–84° in
d, Å
Bond
IIf
IIg
Co(1)–O(1)
Co(1)–O(3)
Co(1)–O(6)
Co(1)–N(1)
Co(1)–N(2)
Co(1)–N(4)
1.8780(12)
1.8737(12)
1.8920(12)
1.9772(14)
1.9410(15)
1.9344(15)
1.890(2)
1.871(2)
1.873(2)
1.967(2)
1.931(2)
1.930(2)
Angle
ω, deg
O(3) Co(1) O(6)
O(3) Co(1) O(1)
O(1) Co(1) O(6)
O(3) Co(1) N(1)
O(6) Co(1) N(1)
O(1) Co(1) N(1)
O(3) Co(1) N(4)
O(6) Co(1) N(4)
O(1) Co(1) N(4)
N(4) Co(1) N(1)
O(3) Co(1) N(2)
O(6) Co(1) N(2)
O(1) Co(1) N(2)
N(2) Co(1) N(1)
N(4) Co(1) N(2)
87.83(5)
86.93(5)
171.39(5)
169.61(6)
101.80(6)
83.95(5)
86.33(6)
93.82(6)
92.66(6)
89.11(6)
94.47(6)
85.11(6)
88.49(6)
90.28(6)
178.64(6)
89.22(9)
91.53(9)
174.00(8)
173.58(10)
95.64(9)
84.07(9)
82.38(9)
94.13(9)
91.87(9)
93.06(9)
92.92(9)
88.55(9)
85.47(9)
91.40(9)
174.54(10)
…
IIg. Despite the fact that the intramolecular C C and
…
C N contacts of the aryl substituents with phenox-
azin-1-one ligand are shortened in all structures, their
values are considerably different, which indirectly
points to their sterically forced nature. A distinctive
feature of the nitro-substituted structure IIg is a sub-
stantial distortion of the phenoxazine ring, resulting in
the boat conformation for the central 6-membered
ring with oxygen and nitrogen atoms deviating from
the plane by ~0.13 Å and folding angle between the
carbon rings and the central ring being ~16°. In all
other complexes, the phenoxazine ring is actually pla-
nar. The comparison of X-ray diffraction data for IIf
and IIg with the previously described IIa and IIb [14]
indicates that the substituents R in the series H, CH3,
OCH3, NO2 do not influence the key structural char-
acteristics of the coordination polyhedron and, hence,
the state of the central cobalt ion.
Crystallographic Data Centre (CCDC no. 1403920
and no. 1403922, respectively; www.ccdc.ac.uk).
RESULTS AND DISCUSSION
All of the obtained adducts II are crystalline com-
pounds stable in the presence of air oxygen (the crys-
tals are dark brown-colored) and can be recrystallized
from solvents of different polarity. As was shown [13,
14], mixed-ligand cobalt complexes II in their ground
low-spin electronic state ls-CoIII-SQ are formed upon
barierless electron transfer, which occurs either via
direct coordination of the redox-active ligand to the
Co(II) complex I or with inclusion of the intermediate
high-spin form of the adduct II' hs-CoII-Q
(Scheme 1). The molecular structure of complexes IIf
and IIg containing electron-donating (OCH3) and
electron-withdrawing (NO2) substituents in the
azomethine moiety was studied by X-ray diffraction
(Fig. 1).
It was found that the reaction of redox active phe-
noxazinone L with I, resulting in the formation of
adducts II, can take place without a solvent in the solid
phase. A nearly quantitative yield of the target product
is attained by thorough grinding of equimolar amounts
of the reactants I and L in an agate mortar. The
described reaction is clearly detected by IR spectros-
copy. Figure 2 presents the absorption bands of the
reactants in the stretching regions of the C=O (phe-
noxazinone L) and C=N (complex I) groups respon-
sible for the formation of the coordination unit of
adducts II. The coordination accompanied by the for-
mation of radical ion adduct II leads to disappearance
of the absorption band of the phenoxazinone ring car-
bonyl group (1640 cm–1) and increase in the intensity
The X-ray diffraction study of cobalt complexes IIf of the azomethine absorption band (C=N) in mixed-
and IIg demonstrated that parameters of the metal ligand complex II. The solid-phase reaction is accom-
coordination polyhedron (distorted octahedron) in panied by color change to give the dark brown crystals
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 4 2016

256
IVAKHNENKO et al.
(а)
С(39)
С(38)
O(4)
С(40)
С(37)
С(36)
С(35)
С(31)
С(41)
С(47)
С(46)
С(18)
С(17)
С(19)
O(2)
С(42)
С(16) N(2)
N(1)
С(30)
С(20)
С(32)
С(45)
O(6)
С(29)
O(3)
Co(1)
С(15)
С(5)
С(33)
С(43)
С(6)
С(3) С(2)
С(34)
С(4)
С(1)
O(1)
С(44)
С(48)
N(4)
С(49)
С(54)
С(50)
С(53)
С(51)
С(52)
O(7)
(b)
С(31)
С(32)
С(30)
С(35)
С(33)
С(34)
O(5)
С(40)
С(41)
N(3)
С(36)
С(37)
O(1)
N(2)
С(29)
С(39)
С(38)
С(3)
С(4)
O(4)
O(3)
С(2)
O(6)
С(47)
С(1)
Co(1)
N(1)
С(46)
С(5)
O(2)
С(42)
С(6)
С(48) С(43)
N(4)
С(49)
С(50)
С(15)
С(16)
С(45)
С(20)
С(54)
С(44)
С(53)
С(52)
С(19)
С(51)
С(18)
С(17)
O(8)
N(5)
O(7)
Fig. 1. Molecular structure of complexes (a) IIf and (b) IIg with atoms represented by probability ellipsoids of displacements (p =
0.5). The hydrogen atoms are omitted.
of the adduct and a sharp change in the volume of the a quantitative yield is faced with procedural difficulties
crystalline mass, due to higher density of the resulting associated with the process of grinding. Since friction
complex. It is noteworthy that obtaining the adducts in takes place on the crystal surface, the inner part of the
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
Vol. 42
No. 4
2016

SYNTHESIS AND STRUCTURE OF POLYCRYSTALLINE ADDUCTS
257
I
0.18
0.17
0.16
0.15
0.14
0.13
0.12
0.11
0.10
0.09
0.08
0.07
0.06
0.05
0.04
0.03
0.02
1
2
3
4
1600
1600
1600
1600
ν, cm–1
Fig. 2. Fragments of the IR spectra: (1) Ia, (2) L, (3) adduct IIa, (4) adduct IIa obtained in toluene as the solvent and recrystal-
lized from acetonitrile.
none ring carbonyl (1640 cm–1) can be recorded even
after long-term grinding of the reactants (Fig. 2).
crystals remains unaffected. In other words, the
amounts of unreacted compounds I and L are related
to the sizes of reacting particles. This assumption is
consistent with the data of IR spectroscopy and pow-
der X-ray diffraction. The presence of trace amount of
the absorption band characteristic of the phenoxazi-
The X-ray powder diffraction pattern of the grind-
ing product corresponds to a new phase and does no
show reflections of the initial phases to within the
instrument sensitivity (2%). However, it does not
coincide with the X-ray diffraction pattern calculated
from the single crystal data, because the solid-phase
synthesis product does not contain solvent molecules
(Fig. 3).
I
The ability of phenoxazinone L to undergo revers-
ible single-electron redox processes to give stable rad-
ical ions (PhenoxSQ) is well known [19, 20]. High sta-
bility of this radical anion is ensured by unpaired elec-
tron shielding by the bulky tert-butyl groups and its
high degree of delocalization in the tricyclic phenox-
azinone system, which is reflected in the HFS con-
1
2
H
H
H
3
stants (aN = 6.32,
a1
= 3.12,
a2
= 3.43,
= 3.39 G).
a3
The HFS constants in the obtained complexes IIс–IIg
were studied by EPR, and the radical ion structure was
established for the complexes. The EPR spectra of a
toluene solution of adducts IIс–IIg in the X-range at
300 K represent a group consisting of 10 HFS lines,
which result from interaction of the unpaired electron
5
10
15
20
25
30
2θ, deg
Fig. 3. Power X-ray diffraction pattern of (1) L, (2) Ia,
(3) adduct IIa.
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 4 2016

258
IVAKHNENKO et al.
(а)
1
2
3400
3440
3480
3520 H, G
(b)
3200 3300 3400 3500 3600 3700
H, G
Fig. 4. EPR spectra of cobalt complex IIс: (a) in toluene ((1) experimental and (2) simulated spectrum); (b) polycrystalline sam-
ple at 300 K.
with nitrogen (S = 3/2) and cobalt (S = 7/2) nuclei induce significant differences in the magnetic proper-
with approximately equal HFS constants (Fig. 4a). ties.
The simulation in terms of this model using the isotro-
Figure 5 shows the dependence of the effective
pic splitting constants aN = 9.45, aCo = 13.45 G (g =
magnetic moment (μeff) on temperature for complexes
2.001) gives a satisfactory agreement between the cal-
IIa and IIb. The decrease in the temperature in the
culated and experimental spectra. Similar values of
300–20 K range changes μeff insignificantly from 2.3 to
HFS constants found for IIa–IIg indicate that substit-
1.8 μB, which implies a paramagnetic state with one
uents in the azomethine moiety have a minor effect on
unpaired electron with the spin S = 1/2, in this partic-
the delocalization of the unpaired electron. The higher
ular case, a low-spin radical ion cobalt complex IIa.
value aN= 9.45 G for cobalt complexes IIa–IIg com-
The curve for μeff vs. temperature in the range of 300–
pared with similar constant in the radical ion potas-
100 K for IIb (Fig. 5b) shows a minor hysteresis. The
sium salt PhenoxSQ (aN = 6.32 G) is attributable to
data of magnetic susceptibility measurements of IIa–
the presence of strong coordination bonds in the radi-
IIg attest to a low-spin electronic state. In the solid
cal ion complexes IIa–IIg. The EPR spectrum of the
phase, the μeff value for such complexes is 1.85 μB,
crystalline powders of IIс–IIg (X-range, 300 K) is the
being almost unchanged in the range of 77–298 K.
exchange-narrowed lines of ~30 G width and g-factor
It turned out that the presence of different substit-
uents in complexes IIa–IIg does not significantly
change their magnetic behavior.
of ~2.00 (Fig. 4b).
The dimeric structure of crystalline IIb and differ-
ent contents of acetonitrile solvent molecules (the
crystal of IIb, unlike unsubstituted IIa, contains two
independent molecules of the cobalt complex and four octahedral mixed-ligand Co(II) complexes capable of
acetonitrile solvent molecules [14]) were found not to intramolecular redox isomerism (valence tautomer-
The proposed approach to the construction of
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY
Vol. 42
No. 4
2016

SYNTHESIS AND STRUCTURE OF POLYCRYSTALLINE ADDUCTS
259
ACKNOWLEDGMENTS
(а)
μeff, μB
This work was supported by the Ministry of Educa-
tion and Science of the Russian Federation as a basic
part of the State Order according to Project no. 1895.
2.5
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0
REFERENCES
1. Christou, G., Polyhedron, 2005, vol. 24, p. 2065.
2. Minkin, V.I. and Starikov, A.G., Izv. Akad. Nauk, Ser.
Khim., 2015, no. 3, p. 475.
3. Hendricson, D.N. and Pierpont, C.G., Top. Curr.
Chem., 2004, vol. 234, p. 63.
4. Kharisov, B.I., Mendez-Rojas, M.A., Garnovskii, A.D.,
et al., J. Coord. Chem., 2002, vol. 55, no. 7, p. 745.
5. Abakumov, G.A., Cherkasov, V.K., Bubnov, M.P.,
et al., Dokl. Ross. Akad. Nauk, 1993, vol. 328, p. 332.
6. Tezgerevska, T., Alley, K.G., and Boskovic, C., Coord.
50
100
150
(b)
200 250 300
T, K
Chem. Rev., 2014, vol. 268, p. 23.
7. Adams, D.M., Dei, A., Rheingold, A.L., and Hen-
drickson, D.N., Angew. Chem., Int. Ed. Engl., 1993,
vol. 32, p. 880.
μeff, μB
8. Adams, D.M., Dei, A., Rheingold, A.L., and Hen-
drickson, D.N., J. Am. Chem. Soc., 1993, vol. 115,
p. 8221.
9. Bhattacharya, S. and Pierpont, C.G., Inorg. Chem.,
2.1
1992, vol. 31, no. 11, p. 2020.
10. Roux, C., Adams, D.M., Itie, J.P., et al., Inorg. Chem.,
1996, vol. 35, p. 2846.
11. Sato, O., Tao, J., and Zhang, Y.-Z., Angew. Chem., Int.
Ed. Engl., 2007, vol. 46, p. 2152.
12. Evangelio, E. and Ruiz-Molina, D., C.R. Chimie, 2008,
vol. 11, p. 1137.
1.8
0
13. Ivakhnenko, E.P., Koshchienko, Yu.V., Knyazev, P.A.,
et al., Dokl. Ross. Akad. Nauk, 2011, vol. 438, no. 4,
p. 485.
14. Antipin, M.Yu., Ivakhnenko, E.P., Koshchien-
ko, Yu.V., et al., Izv. Akad. Nauk, Ser. Khim., 2013,
no. 8, p. 1744.
50
100
150
200
250
300
T, K
15. Kogan, V.A., Osipov, O.A., and Lempert, L.E., Zh.
Neorg. Khim., 1967, vol. 12, no. 6, р. 304.
16. Sheldrick, G.M., Acta Crystallogr., Sect. A: Found.
Crystallogr., 2008, vol. 64, p. 112.
Fig. 5. Temperature dependence of μ for cobalt com-
eff
plexes: (a) IIa, (b) IIb.
17. Bhattacharya, S., Gupta, P., Basuli, F., and
Pierpont, C.G., Inorg. Chem., 2002, vol. 41, p. 5810.
ism) opens up the possibility of using a broad range of
tetrahedral metal chelates with different structures of
the coordination unit for the design of systems with
magnetically controlled properties. The high cyclabil-
ity of the redox isomerization in complexes of this type
is provided by the intramolecular electron transfer
mechanism requiring no significant structural rear-
rangement of ligands.
18. Filippenko, O.S., Aldoshin, S.M., Ivakhnenko, E.P.,
et al., Dokl. Ross. Akad. Nauk, 2000, vol. 370, p. 345.
19. Stegmann, H.B. and Scheffler, K., Chem. Ber., 1968,
vol. 101, p. 262.
20. Karsanov, I.V., Ivakhnenko, E.P., Khandkarova, V.S.,
et al., J. Organomet. Chem., 1989, vol. 379, p. 1.
Translated by Z. Svitanko
RUSSIAN JOURNAL OF COORDINATION CHEMISTRY Vol. 42 No. 4 2016