Zero-field splitting in tetracoordinate Co(II) complexes

Article abstract of DOI:10.1016/j.poly.2012.01.023

Mononuclear Co(II) complexes of the [CoCl₂L₂] family, with L being a heterocyclic N-donor ligand, were subjected to magnetochemical investigation. The temperature dependence of the magnetic susceptibility and the field dependence of the magnetization have been analyzed simultaneously in terms of the spin Hamiltonian formalism. The magnetic parameters obtained by a fitting procedure show a considerable magnetic anisotropy measured by the g-factor difference and the zero-field splitting parameter 2D, that splits the ground term ⁴B₁(D_2d) and/or ⁴A ₂(C_2v).

Full text of DOI:10.1016/j.poly.2012.01.023

Polyhedron 36 (2012) 79–84
Contents lists available at SciVerse ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Zero-field splitting in tetracoordinate Co(II) complexes
a
b
b
a
a,b,
⇑
ˇ
ˇ
M. Idešicová , L. Dlhá nˇ , J. Moncol , J. Titiš , R. Bo cˇ a
a
Department of Chemistry, FPV, University of SS Cyril and Methodius, 91701 Trnava, Slovakia
Institute of Inorganic Chemistry, FCHPT, Slovak University of Technology, 812 37 Bratislava, Slovakia
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Mononuclear Co(II) complexes of the [CoCl L ] family, with L being a heterocyclic N-donor ligand, were
2
2
Received 11 January 2012
Accepted 21 January 2012
Available online 8 February 2012
subjected to magnetochemical investigation. The temperature dependence of the magnetic susceptibility
and the field dependence of the magnetization have been analyzed simultaneously in terms of the spin
Hamiltonian formalism. The magnetic parameters obtained by a fitting procedure show a considerable
magnetic anisotropy measured by the g-factor difference and the zero-field splitting parameter 2D, that
splits the ground term
Keywords:
Co(II) complexes
Magnetism
4
(D2d) and/or 4
1 2
B A (C2v).
Ó 2012 Elsevier Ltd. All rights reserved.
Electronic spectra
Heterocyclic ligands
Zero-field splitting
1
. Introduction
The zero-field splitting is a fine structure of the electronic en-
2 2
ylpyrazole, NO dmiz – nitro-N-dimethylimizadole, NH pymd – 2-
aminopyrimidine, bziz – benzimidazole). These complexes have
been already structurally characterized and the corresponding data
can be retrieved from the Cambridge Crystallographic Data Centre
[9–14]. Molecular structure of complexes under study is displayed
in Fig. 1. For the purpose of a magnetostructural correlation the X-
ray structure has been redetermined for them.
ergy levels that appears as a result of the splitting of the crystal-
field terms into crystal-field multiplets. It is characterized by the
axial zero-field splitting parameter D that is related to the energy
gap between the ground and excited states. The sign of the D-
parameter is either negative or positive and it adopts values be-
tween 10 and 10 cm [1]. A tailoring of the D-parameter is
far from the routine, though there is a need of this when tuning
the properties of the single-molecule magnets. Some insights to
this target brought the magnetostructural D-correlations that bring
a linear relationship between the axial distortion of the octahedron
and the D-parameter in a series of Ni(II) hexacoordinate complexes
ꢀ2
2
ꢀ1
2. Experimental
2.1. Synthesis
The compound A, [CoCl
A solution of 0.47 g (0.19 mmol) of CoCl
2
(dmpz)
2
], has been prepared as follows.
[
2–7]. For hexacoordinate Co(II) complexes the magnetostructural
2
ꢂ6H
2
O in 10 cm3 of THF
D-correlation has also been outlined [8].
was slowly added to the solution of 0.38 g (0.39 mmol) of dmpz
3
The present communication represents a step forward in get-
ting magnetostructural D-correlations for tetracoordinate Co(II)
complexes. The collection of reliable structural and magnetic data
for the latter purpose represents the aim of this study. In tetraco-
ordinate Co(II) complexes the orbitally nondegenerate ground
term A
the ground and excited multiplets (each referring to a Kramers
doublet jS; M i) separated by 2D ¼ Eðj3=2; ꢁ3=2iÞ ꢀ Eðj3=2; ꢁ1=2iÞ.
A series of Co(II) complexes of the [CoCl ] type was studied,
namely A = [CoCl (dmpz) ], B = [CoCl (NO dmiz) ], C = [CoCl (NH2-
pymd) ], and D = [CoCl (bziz) ] (abbr. for ligands dmpz – 3,5-dimeth-
in 10 cm of THF under an intense stirring (the molar ratio dmpz:
CoCl
2
ꢂ6H
2
O = 2:1). The mixture was refluxed under THF for 1 h
after which the solution was filtered off. The filtrate was left for
3 days for a spontaneous evaporation. The dark blue crystals were
separated on Büchner funnel.
4
4
4
4
4
(T
2 d
) ? B
1
(D2d) ? A
2
(C2v) ? A’’(C
s
) ? A(C
1
) is split into
The compound B, [CoCl
lows. A solution of 0.23 g (0.1 mmol) of CoCl
ethanol was added to the solution of 0.28 g (0.2 mmol) of NO
2
(NO
2
dmiz)
2
], has been prepared as fol-
ꢂ6H
O in 10 cm3 of
dmiz
in 15 cm of ethanol under an intense stirring (the molar ratio
NO dmiz: CoCl O = 2:1). Deep blue crystals were obtained by
2
2
S
2
3
2 2
L
2
2
2
2
2
2
2
2
ꢂ6H
2
2
2
2
slow evaporation of the solution at room temperature.
The remaining complexes were prepared by a similar recipe.
Anal. Calc. for A, C10
17.4. Found: C, 36.8; H, 4.90; N, 17.1%. Anal. Calc. for B, C10
CoCl (M = 412.1): C, 29.1; H, 3.42; N, 20.4. Found: C, 28.3; H, 3.56;
16 4 2
H N CoCl (M = 322.10): C, 37.3; H, 5.01; N,
⇑
Corresponding author at: Department of Chemistry, FPV, University of SS Cyril
and Methodius, Trnava, Slovakia. Tel.: +421259325610.
14 6 4-
H N O
E-mail address: roman.boca@stuba.sk (R. Bo cˇ a).
2
0
277-5387/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2012.01.023

8
0
M. Idešicová et al. / Polyhedron 36 (2012) 79–84
were scanned in the temperature range 2–300 K at the applied field
of B = 0.1 T. The magnetization has been measured at T = 2.0 and
4
.6 K. Raw data were corrected for the underlying diamagnetism
ꢀ
12
3
ꢀ1
ꢀ1
using estimate of
v
dia/(10
m mol ) = 5M[gmol ].
2.3. X-ray crystallography
Data collection and cell refinement of A through D were carried
out using a -axis diffractometer Gemini R CCD (Oxford Diffrac-
tion) with graphite monochromated Mo K radiation. The diffrac-
j
a
tion intensities were corrected for Lorentz and polarization factors.
The structures were solved by direct methods using SIR-97 [15] or
SHELXS-97 [16] and refined by the full-matrix least-squares proce-
dure with SHELXL-97 [16]. The analytical [17] or multi-scan absorp-
tion corrections were made by using CRYSALIS-RED [18].
Geometrical analyses were performed with SHELXL-97. Crystal data
and conditions of data collection and refinement are reported in
Table 1. Photographs of the single crystals used in the X-ray struc-
ture determination are shown in the Supplementary data.
Fig. 1. Molecular structure of complexes under study; CCDC code is attached.
Hydrogen atoms are omitted for clarity.
N, 20.2. Anal. Calc. for C, C
8
H
10
N
6
CoCl
.15; N, 26.3. Found: C, 30.3; H, 3.20; N, 27.0%. Anal. Calc. for D,
CoCl (M = 366.11): C, 45.9; H, 3.30; N, 15.3. Found: C,
5.9; H, 3.40; N, 15.5%.
2
(M = 320.04): C, 30.0; H,
3
C
4
14
H
12
N
4
2
2.2. Physical measurements
3. Results and discussion
Elemental analysis was carried out on FlashEA 1112 (Thermo-
3.1. Structural data
Finnigan). Electronic spectra were measured in Nujol mull (Specord
ꢀ
1
2
00, Analytical Jena) in the range 9000–50000 cm . Magnetic data
The molecular structures with thermal ellipsoids of A, B, C and
D are presented in Supplementary data (Figs. S1–S4). In all cases
were taken with the SQUID magnetometer (MPMS-XL7, Quantum
Design) using the RSO mode of detection. The susceptibility data
the chromophore {CoCl
2
N
2
} refers to a distorted tetrahedron. The
Table 1
Crystallographic data.
Compound
A
B
C
D
[
CoCl
2
(dmpz)
2
]
[CoCl
2
(NO
2
dmiz)
2
]
[CoCl
10Cl
320.05
2
(NH
2
pymd)
2
]
[CoCl
12Cl
366.11
2
(benzim)
2
]
Chemical formula
C
10
H
16Cl CoN
2
4
C
10
H14Cl
2
CoN
6
O
4
C
8
H
2
CoN
6
C
14
H
2
CoN
4
M
322.10
412.10
Cell setting, space group
monoclinic, C2/c
298(2)
tetragonal, I-42d
298(2)
11.4367(4)
11.4367(4)
25.811(3)
90.0
90.0
90.0
3376.1(4)
8
monoclinic, C2/c
298(2)
triclinic, P1ꢀ
293(2)
T (K)
a (Å)
b (Å)
c (Å)
15.0121(3)
8.2726(2)
24.0518(5)
90.0
96.033(2)
90.0
10.6381(3)
13.2780(4)
8.8554(2)
90.0
97.658(3)
90.0
7.4794(9)
7.7532(4)
13.2794(16)
85.670(7)
86.081(10)
82.966(7)
760.73(14)
1
a
(°)
b (°)
(°)
c
3
V (Å )
Z
2970.43(11)
8
1239.69(6)
4
Radiation type
Mo K
1.360
a
Mo K
1.500
a
Mo K
1.801
a
Mo K
1.476
a
ꢀ
1
l
(mm
)
Crystal size (mm)
Diffractometer
Abs. correction
0.28 ꢃ 0.27 ꢃ 0.21
Gemini R CCD
analytical
0.82 ꢃ 0.53 ꢃ 0.14
Gemini R CCD
analytical
0.26 ꢃ 0.22 ꢃ 0.15
Gemini R CCD
multi-scan
0.31 ꢃ 0.25 ꢃ 0.23
Gemini R CCD
multi-scan
T
min, Tmax
0.702, 0.763
27275/1473
1.061
0.0370, 0.1102, 0.1011
1717/0/106
0.322, 0.193
848839
0.373, 0.818
22672/2544
1.034
0.0247, 0.0674, 0.0206
3033/0/154
0.221, 0.190
848840
0.652, 0.774
9447/1152
1.070
0.0190, 0.0538, 0.0187
1259/0/78
0.172, 0.167
801981
0.649, 0.729
6405/2645
1.043
0.0323, 0.0851, 0.0252
3077/0/190
0.333, 0.330
848841
Measure reflections, observed reflections [I > 2r(I)]
S
R
Data/restrains/parameters
D
CCDC code
[F2 > 2
r
(F )], wR
2
(F ), Rint
2
1
2
ꢀ
3
q
max
,
D
q
min (eÅ
)
Fig. 2. 1D supramolecular band chain from molecules A connected by N–H. . .Cl hydrogen bonds. Hydrogen atoms are omitted for clarity.

M. Idešicová et al. / Polyhedron 36 (2012) 79–84
81
Fig. 3. 2D supramolecular framework from molecules C connected by N–H. . .Cl hydrogen bonds. Hydrogen atoms are omitted for clarity.
by two neighboring benzene rings [C2–C7] with C
g
. . .C
g
distance
3
.46 Å (distance between two planes of benzene rings is 3.67 Å),
as well as by two neighboring imidazole rings [C1N1C2C3N2] with
. . .C distance 3.35 Å (distance between two planes of pyrimidine
rings is 3.47 Å). The second benzimidazole ligand is stacked with
distance between two planes of 3.51 Å, and C . . .C distances [ben-
C
g
g
g
g
zene–benzene and benzene–imidazole] are 3.75 and 3.72 Å,
respectively (Fig. 4).
3.2. Electronic spectra
The electronic spectra of complexes are essentially similar
ꢀ1
(
Fig. 5): in the range of 9000–23000 cm they exhibit a number
d–d transitions which are followed by an intense charge transfer
ꢀ1
band. The first visible transition is a broad band at ca 9000 cm
,
the second is split into three peaks between 16000 and
ꢀ1
1
8000 cm (eij = eji, mij = mji). Since the structure of the complexes
is derived from a tetrahedron, the interpretation of the spectra was
done in the T group of symmetry in the first approximation.
The estimate for the crystal field strength for tetrahedral sys-
tems is Dq(T ) = (4/9)Dq(O ) = (4/9)(1/6)F (R). Therefore the first
) lies in the NIR region and it has not been
detected by the used hardware.
The first observed band refers to the A
d
d
h
4
4
4
transition
1 2 2
D ( A to T
4
to 4T
2
1
(F) transition and
2
D = 18Dq = 9000 cm . However, the configu-
ꢀ
1
its energy is about
ration interaction between
causes a reduction of the energy for this transition. An estimate
4
4
1 1
T (F). . . T (P) terms is effective and
Fig. 4. (A) 2D supramolecular framework from molecules D connected by N–H. . .Cl
hydrogen bonds. (B) stacking interaction between benzimidazole rings.
4
4
p–
p
for the last allowed d–d transition
A
2
to
T
1
(P) is
D
3
¼ 12Dqþ
ꢀ1
Hydrogen atoms are omitted for clarity.
1
5B; using Dq = 500 cm the Racah parameter of Co(II) is esti-
mated as B = 733 cm . This value is lowered relative to the free-
ꢀ1
ꢀ1
ion value (B
0
= 980 cm ) owing to the nephelauxetic effect.
The assignment of the bands in the 16000–18000 cm region
ꢀ1
complete molecules A and D lie in the independent part cell,
whereas the molecules B and C lie on the 2-fold axes and only
halves of molecules lie in the independent part cell.
4
4
is a bit intricate since the
T
1g(P) mother term is split into { A
2
,
4
E} daughter terms in the more realistic D2d (or C2v) group of sym-
2
The molecules of A are interconnected through N–H. . .Cl hydro-
gen bonds [19,20] to 1D supramolecular band chains (Fig. 2). On
the other hand, the molecules C and D are connected through N–
H. . .Cl and N–H. . .N (only C) hydrogen bonds to 2D supramolecular
frameworks (Figs. 3 and 4). The hydrogen bonds in crystal packing
metry. Moreover, the close-lying E(G), 2A (G), 2T (G) and 2
1 1 2
T (G)
terms might borrow the intensity from the spin-allowed transi-
tions. The spin–orbit coupling is also in the play and it further
modifies the term scheme.
A modeling of the crystal-field terms, as described in details
elsewhere [22], brings answer; using the crystal-field poles
of C and D are supported by weak
between aromatic rings. The stacking interactions in C are ob-
tained between two neighboring pyrimidine rings [N2C1N1C2–C4]
with C . . .C distance 3.72 Å and distance between two planes of
pyrimidine rings is 3.57 Å (Fig. 3). The stacking interactions
in D are more complex. One of benzimidazole ligands is stacked
p–p stacking interactions [21]
ꢀ1
p–p
4
F = 7200, B = 700 and C = 2800 cm the calculated energy spec-
4
4
4
(F) – 9020, 2E(G) –
(P) – 17480, 2T
(G) –
(G) and
trum is:
13230, 2T
17880, and
2 2 1
A (ground term), T – 5330, T
2
(G) – 16530, 4T
(G) – 19225 cm . Indeed, the terms
g
g
1
(P) – 13530,
A
1
1
2
2
ꢀ1
2
p
–p
T
1
A
1
4
1
T (P) are close in energy.

8
2
M. Idešicová et al. / Polyhedron 36 (2012) 79–84
2T2(G)
0.6
0.4
0.2
0.0
calculated
4
4P
T1(P)
4
4
A + E
2
A
B
C
D
2T1(G)
1
5B
2G
Δ3 > 15B + 12Dq
CI
2A
(G)
1
2E(G)
Δ < 18Dq
4B+3C
2
4
T1(F)
4
4
A + E
2
8
Dq
4F
4
4
B + E
2
Δ1
4T2
10Dq
4B1
4A2
9
000 11000 13000 15000 17000 19000 21000 23000
flattening
Wavenumber/cm-1
D2d
Td
R3
Fig. 5. Electronic spectra measured in Nujol mull. Stacks – calculated positions of transitions; red labels – spin forbidden. Right – crystal field terms (not to scale) for
tetracoordinate Co(II) complexes. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)
3.3. Magnetic data
1 A B
per formula unit is only M = Mmol/(N l ) = 2.31. This subnormal
value again reflects a considerable zero-field splitting.
The magnetic data have been fitted by assuming the anisotropic
spin Hamiltonian in the form
The magnetic functions for complexes A through D are dis-
played in Fig. 6.
For the complex A, the room-temperature value of leff = 4.64 l
B
matches the S = 3/2 spin system with some orbital contribution to
the g-factor (gav ꢄ 2.4). On cooling the effective magnetic moment
slightly decreases along a straight line which is a fingerprint of
some temperature-independent paramagnetism. Below 50 K the
2
ꢀ2
ꢀ1
a
^
^
^
H
a
¼ D½S ꢀ SðS þ 1Þ=3ꢅ ꢀh þ galBBS
ꢀh
ð1Þ
z
(a = z, x) where D is the zero-field splitting parameter and the
second contribution is the spin Zeeman term. The minor improve-
ments refer to the molecular-field correction zj (sensitive to the
low-temperature window) and the uncompensated temperature-
decrease is more rapid until 3.50
B
l at 1.9 K; this reflects a zero-
4
field splitting (the splitting of the ground
1
B (D2d) term into two
Kramers doublets). The magnetization data taken at T = 2.0 K
shows features of a saturation at B = 7.0 T but the magnetization
independent magnetism
data)
vTIM (that affects the high-temperature
Fig. 6. Magnetic functions for A through D. Left – temperature dependence of the effective magnetic moment, right – field dependence of the magnetization. Circles –
experimental data. Lines – fitted data with magnetic parameters listed in Table 2.

M. Idešicová et al. / Polyhedron 36 (2012) 79–84
83
Table 2
a
Key magnetic data and fitted magnetic parameters.
D/hc (cm 1
ꢀ
)
(zj)/hc (cm
ꢀ1
)
v
TIM/109 (m mol
3
ꢀ1
)
R(v) (%)
R(M) (%)
Compound
leff @ 300 K
leff @ 2 K
M
1
@ 2 K, 7 T
g
z
g
x
A
B
C
D
4.64
4.53
4.49
4.46
3.50
2.88
2.79
3.21
2.31
2.60
2.69
3.24
2.000
2.163
2.161
2.538
2.350
2.302
+41.5
+11.4
+12.2
ꢀ3.15
0.055
0.18
0.217
0.093
3.00
+3.75
+5.00
–
0.45
0.53
0.80
4.5
2.4
7.7
4.9
3.1
g
iso 2.290
a
ꢀ1
Estimated errors: 0.01 for g-factors, 1.0 cm for the D-parameter.
vmol
doublet
M ¼ ꢁ1=2;
S
the
limiting
value
is
vcorr ¼ 1
þ
vTIM
ð2Þ
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
ꢀ ðzj=N
A
l0l2
Þ
vmol
leff ðLTÞ ¼
g
2
=4 þ 2g
2
l
B
z
irrespective of D. With g = 2.0 and
B
z
x
g
x
= 2.54 one gets
l
ðLTÞ = 3.73
B
l . Lower values eventually ob-
eff
When the D-value is low, the g-factor anisotropy is also small
and then it cannot be determined reliably from the bulk suscepti-
bility and magnetization data. In such a case (the complex D), the
isotropic g-value has been considered.
served at T ꢄ2 K are attributed to the presence of intermolecular
interactions described by the molecular field correction [24,25].
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
2
2
The high-temperature limit is leff ðHTÞ ¼ ð5=4Þðg þ 2g ÞlB
z
x
which with the above g-values yields
l
ðHTÞ = 4.60
B
l , again irre-
eff
An advanced fitting procedure accounts simultaneously for the
spective of D. To this end, the susceptibility data are almost insen-
sitive to the sign and magnitude of D. On the other hand, these
serve for a reliable determination of the g-factors.
two data-sets:
and 4.6 K, respectively. The powder average has been done by aver-
aging 210 points of polar coordinates a ꢆ ð# uiÞ distributed over
the top hemisphere. The quality of the fit is good as expressed by
v
¼ fðT; B
0
¼ 0:1TÞ and M ¼ fðB; T
0
Þ with T
0
= 2.0
i
;
The sensitive probe in determining the D-values is the magne-
tization at intermediate fields (5–7 T) that reflects a declination
from the Brillouin function. For the principal components of the
magnetization some closed formulae have been derived [1,23];
these, however, cannot be used for the true powder average when
the magnetic field is oriented in any direction. This is solved by a
fully numerical approach by considering the magnetic field distrib-
uted uniformly over 210 points at the hemisphere. Moreover, the
g-values are correlated with D: in the saturation limit of the mag-
netization the higher g requires the higher D and vice versa. The
application of a combined functional (the relative error of suscep-
tibility multiplied by the relative error of magnetization) solves the
above dilemma: the g and D values can be fixed reliably. The expe-
rience shows that using different trial sets, the magnetic parame-
discrepancy factors for the susceptibility R(
v) and magnetization
R(M).
The final set of magnetic parameters is listed in Table 2. It can
be seen that the complex A possess large g-factor anisotropy along
with the sizable axial zero-field splitting parameter D/hc =
ꢀ1
4
2 cm . The spin-Hamiltonian offers a constraint
D
SH ¼ kðg ꢀ g Þ=2
ð3Þ
z
x
where the spin–orbit splitting parameter k ¼ ꢀnCo=2S for Co(II) is
ꢀ
1
k/hc = ꢀ172 cm . Then the estimate of the axial zero-field splitting
ꢀ1
parameter is DSH/hc = 46 cm that matches the value obtained by
data fitting.
ters are reproduced within the tolerance of 0.01 for g-factors and
For the S = 3/2 system the closed formulae for the components
of the susceptibility are available [1,23]. They can be used in deter-
mining the limiting values as follows. For large D, the low-temper-
ature susceptibility data are dominated by the lower Kramers
1
1
.0 cm for the D-parameter, respectively.
The magnetic data for the complexes B through D are in many
respects analogous to those for A (Fig. 6). The observed limiting
Table 3
Magnetic and structural parameters sorted according to D.
D (cm 1
ꢀ
)
g
g
Ref.
Compound
Chromophore {CoA
2
B
2
}
Co-A Co-B
A-Co-A B-Co-B
z
x
1
2
3
4
5
6
7
[Co(salbim)
2
]
{CoN
2
O
2
}
1.976, 1.958
120.9(1ꢃ)
+66.7
2.000
2.000
2.161
2.163
2.600
2.538
2.302
2.350
[26]
a
1
.909, 1.914
2.238
.005
2.243
.041
2.231
.034
114.2(1ꢃ)
[CoCl
[CoCl
[CoCl
2
2
2
(dmpz)
(NH pymd)
(NO dmiz)
2
]
{CoCl
{CoCl
{CoCl
2
N
2
N
2
N
2
}, C2v
}, C2v
}, C2v
118.1(1ꢃ)
105.7(1ꢃ)
110.4(1ꢃ)
114.5(1ꢃ)
111.0(1ꢃ)
102.4(1ꢃ)
113.5(2ꢃ)
+41.5
+12.2
+11.4
+10.6
A
2
2
2
]
2
2
C
2
2
2
]
B
2
Hg[Co(NCS)
(NEt [CoL
Cs CoCl
4
]
{CoN
Single crystal
{CoO
4
}, D2d
1.964
g
iso 2.22
[27,28]
[29]
[30,31]
+10.2,+10.8
+5.4
2.168
2.20
2.251
2.29
b
)
4 2
2
]
2
S
2
}
1.958, 1.980
109.7(1ꢃ)
2
.284, 2.248
2.258, 2.258
.263, 2.267
130.3(1ꢃ)
109.3(1ꢃ)
116.6(1ꢃ)
2
4
{CoCl
4
}, C
s
(+3) estimate
2
1
1
09.5(2ꢃ)
05.8(2ꢃ)
8
[CoCl
2
(bziz)
2
]
{CoCl
2
N
2
}, C
1
2.241, 2.254
.004, 2.010
111.9(1ꢃ)
106.2(1ꢃ)
107.2(2ꢃ)
107.6(2ꢃ)
118.9(1ꢃ)
113.1(1ꢃ)
117.3(1ꢃ)
115.9(1ꢃ)
ꢀ3.15
g
iso 2.290
D
2
9
1
1
Cs
Cs
3
CoCl
CoBr
5
{CoCl
{CoBr
{CoCl
4
}, D2d
}, D2d
}, C
2.268
2.399
2.264, 2.284
ꢀ4.30 EPR
ꢀ5.34 EPR
ꢀ12.0
2.40
2.42
2.362
2.30
2.32
2.225
[32,33]
[32,34]
[35]
0
1
3
5
4
(Hiz)
2
[CoCl
4
]
4
1
c
2
.270, 2.291
2.212
.384
1
2
[Co(PPh
3 2
) Cl
2
]
{CoCl
2
P
2
}, C2v
ꢀ14.76 EPR E, 1.14
2.240
2.166
2.170
[36,37]
2
a
0
0
0
0
For 1 – angles within one bidentate ligand are fixed: N–Co–O = 94.9, N –Co–O = 94.2°; angles between different ligands N–Co–O = 111.8, N –Co–O = 121.9, N–Co–
0
b
N = 120.9, O–Co–O’ = 114.2°.
For 6 L = CPh
2
(SH)(COO); angles within one bidentate ligand are 87.3 and 88.5°.
c
For 11 – other angles 110.3, 106.7, 104.6, 104.1°.

8
4
M. Idešicová et al. / Polyhedron 36 (2012) 79–84
values are listed in Table 2 along with the final set of magnetic
parameters. Again a sizable zero-field splitting is indicated, that
has been confirmed by the data fitting. For instance, for B the D-
parameter amounts to D/hc = 11.4 (16.1) cm where the value in
parentheses refer to the constrained D-value calculated using the
g-factor anisotropy.
033; or e-mail: deposit@ccdc.cam.ac.uk. Supplementary data asso-
ciated with this article can be found, in the online version, at
doi:10.1016/j.poly.2012.01.023.
ꢀ1
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4
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[
[
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(
CCDC-RESYUJ, R = 0.036).
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(
[
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s 1
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{
CoA } chromophores were observed. To this end, a more rich
2
B
2
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4
. Conclusions
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L
2
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(
have been prepared and structurally characterized. Their chro-
mophores {CoCl } exhibit distortions from the tetrahedral pat-
tern that refer to the C2v symmetry for A, B and C and C in the
complex D. These distortions support the zero-splitting of the
[
[
21] C. Janiak, J. Chem. Soc., Dalton Trans. (2000) 3885.
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2 2
N
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4
4
4
4
ground crystal-field term
A
2
(T
d 1 2
) ? B (D2d) ? A (C2v) ? A’’(C-
4
ˇ. Dlhá nˇ , I. Nemec, B. Papánková, J. Pavlik, H. Fuess, Inorg.
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) ? A(C ) into crystal-field multiplets that refer to a pair of Kra-
1
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ˇ
ˇ
[
[
27] D. Nelson, L.W. ter Haar, Inorg. Chem. 32 (1993) 182.
ꢀ1
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.
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0
[
29] N. Duran, W. Clegg, L. Curucull-Sanchez, R.A. Coxall, H.R. Jimenez, J.-M.
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Acknowledgments
[
Slovak grant agency VEGA (Projects 1/0052/11 and 1/0233/12)
is acknowledged for the financial support.
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R = 0.026).
(
[
[
[
3
Appendix A. Supplementary data
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0.021).
CCDC 848839, 848840, 801981 and 848841 contain the supple-
mentary crystallographic data for A through D. These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/conts/
retrieving.html, or from the Cambridge Crystallographic Data Cen-
tre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336
[
35] A. Bienko, K. Suracka, R. Bo cˇ a, to be published.
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(1982) 2218 (CCDC-BIHGEE, R = 0.042).