Supramolecular cobalt(II) complexes: Syntheses, crystal structures and solvent effects

Article abstract of DOI:10.1007/s11243-010-9394-6

Two Co^II complexes, namely {[CoL(MeOH)(μ-OAc)] ₂Co}?2MeCN?2MeOH (1) and {[CoL(EtOH)(μ-OAc)] ₂Co}?3EtOH (2) (H₂L=3,3′-dimethoxy-2,2′- [(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol), have been synthesized

Full text of DOI:10.1007/s11243-010-9394-6

Transition Met Chem (2010) 35:787–794
DOI 10.1007/s11243-010-9394-6
Supramolecular cobalt(II) complexes: syntheses,
crystal structures and solvent effects
•
Wen-Kui Dong Li Li Yin-Xia Sun
•
•
•
Jun-Feng Tong Jian-Chao Wu
Received: 12 April 2010 / Accepted: 25 June 2010 / Published online: 11 July 2010
Ó Springer Science+Business Media B.V. 2010
Abstract Two CoII complexes, namely {[CoL(MeOH)-
(l-OAc)]2Co}ꢀ2MeCNꢀ2MeOH(1) and {[CoL(EtOH)(l-OAc)]2-
Co}ꢀ3EtOH (2) (H2L=3,30-dimethoxy-2,20-[(1,3-propylene)
dioxybis(nitrilomethylidyne)]diphenol), have been synthe-
sized and characterized by X-ray crystallography. Both
complexes contain octahedral coordination geometries,
comprising three CoII atoms, two deprotonated bisoxime
L2- units in which four l-phenoxo oxygen atoms form two
[CoL(X)] (X = MeOH or EtOH) units, two acetate ligands
coordinated to three CoII centers through Co–O–C–O–Co
bridges, and coordinated and non-coordinated solvent. Both
complexes exhibit 2D supramolecular networks through
different intermolecular hydrogen-bonding interactions.
and study of the magnetic, photoelectric and catalytic
properties of such complexes.
To generate target complexes by design, a judicious
choice of ligands is required in order to control the
supramolecular interactions. In general, ligands with fea-
tures such as rigidity and symmetry are suitable for
obtaining coordination supramolecules. With this in mind,
we have explored Salen-type bisoxime ligands. These can
provide N and O donor sites, which together with aromatic
rings may form hydrogen bonds and p–p stacking inter-
actions to extend and stabilize the resulting framework.
Hence, diverse supramolecular structures may result from
this interesting ligand.
Herein, two trinuclear CoII complexes, namely {[CoL(MeOH)-
(l-OAc)]2Co}ꢀ2MeCNꢀ2MeOH (1) and {[CoL(EtOH)(l-OAc)]2 -
Co}ꢀ3EtOH (2) (H2L = 3,30-dimethoxy-2,20-[(1,3-propyl-
ene)dioxybis(nitrilomethylidyne)]diphenol), have been syn-
thesized and characterized. X-ray crystallographic analyses
reveal that the structures of the complexes are pseudo-
isostructural, in that they are both trinuclear, with two
acetates coordinated to three CoII atoms through Co–O–C–
O–Co bridges and four l-phenoxo oxygen atoms from two
[CoL(X)] (X = MeOH or EtOH) units also coordinated to
CoII.
Introduction
The self-assembly and synthesis of metal–organic com-
plexes with supramolecular architectures is now a mature
research field [1]. The development of new metal–organic
complexes can provide new topologies for functional
materials, in which pore size, coordination forms and func-
tionality are all important variables [2]. Supramolecular
complexes in which the metal centers are bridged through
organic ligands are of much current interest, because of their
enormous variety of structural topologies and as well as their
potential applications in optoelectronics, magnetism and
catalysis [3–10]. This subject is currently being pursued in
our research, including the use of functional oxime groups
Experimental
4-Methoxy-2-hydroxybenzaldehyde (C98%) from Alfa
Aesar was used without further purification. The other
reagents and solvents were analytical grade reagents from
Tianjin Chemical Reagent Factory and were used without
further purification. Elemental analyses for Co were
determined with an IRIS ER/SꢀWP-1 ICP atomic emission
spectrometer. C, H and N analyses were obtained with a
W.-K. Dong (&) ꢀ L. Li ꢀ Y.-X. Sun ꢀ J.-F. Tong ꢀ J.-C. Wu
School of Chemical and Biological Engineering, Lanzhou
Jiaotong University, 730070 Lanzhou, Gansu, China
e-mail: dongwk@126.com
123

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Transition Met Chem (2010) 35:787–794
Preparation of complex 2
GmbH VariuoEL V3.00 automatic elemental analyzer.
FTIR spectra were recorded on a VERTEX70 FTIR
spectrophotometer, with samples prepared as KBr
(500–4,000 cm-1) or CsI (100–500 cm-1) pellets. UV–vis
spectra were taken on a Shimadzu UV-240 spectropho-
tometer. 1H NMR spectra were recorded on a Mercury-
400BB spectrometer at room temperature using CDCl3 as
solvent. Electrolytic conductance measurements were
made with a DDS-11A type conductivity bridge using
1.0 9 10-3 mol L-1 solutions in DMF at room tempera-
ture. Melting points were measured with a microscopic
melting point apparatus made by the Beijing Taike
Instrument Limited Company, and the thermometer was
uncorrected. TG-DTA analyses were carried out at a
heating rate of 5 °C/min in the temperature range
25–900 °C on a ZRY-1P thermoanalyzer, using an Al2O3
crucible.
The synthesis of complex 2 was similar to complex 1,
except that Co(OAc)2ꢀ4H2O was dissolved in ethanol.
Found: C, 49. 4; H, 5.8; N, 4.7; Co, 13.7. Calcd. for
C52H76Co3N4O21 (%): C, 49.2; H, 6.0; N, 4.4; Co, 13.9.
Crystal structure determinations
Single crystals suitable for data collection were selected
and glued to the tip of a glass fiber. The determination of
the crystal structures at 153 K and 298 K for complexes 1
and 2 were carried out with a Rapid Auto Version 3.0
Rigaku RAXIS-RAPID detector and Bruker Smart APEX
II CCD diffractometer, respectively. Both diffractometers
used graphite-monochromated Mo–Ka radiation (k =
˚
0.71073 A). The LP factor semi-empirical absorption cor-
rections were applied using the SADABS program [15].
The structures were solved by direct methods and refined
by the full-matrix least-squares method on F2 using the
SHELXTL crystallographic software package [16]. All
non-hydrogen atoms were refined with anisotropic thermal
parameters. Hydrogen atoms were placed in calculated
positions and included in the final cycles of refinement
using a riding model. A summary of the key crystallo-
graphic information is given in Table 1, and the final
positional and thermal parameters are available as sup-
plementary material.
Synthesis of H2L
1,3-Bis(aminooxy)propane was synthesized by a similar
method to that reported earlier [11–13]. 3,30-Dimethoxy-
2,20-[(1,3-propylene)dioxybis(nitrilomethylidyne)]diphenol
(H2L) was synthesized according to a method analogous
to that reported earlier [12–14]. To an ethanol solution
(10 mL) of 4-methoxy-2-hydroxybenzaldehyde (62.5 mg,
0.41 mmol) was added an ethanol solution (5 mL) of 1,3-
bis(aminooxy)propane (21.8 mg, 0.21 mol). The mixture
was stirred at 55 °C for 4 h. After cooling to room temper-
ature, the precipitate was filtered off and washed succes-
sively with ethanol and ethanol/n-hexane (1:3, V/V). The
product was dried under vacuum, and obtained as a colorless
Results and discussion
Two solvent-induced supramolecular CoII complexes have
been synthesized and characterized (Scheme 1). Both
complexes are soluble in DMF, DMSO and CHCl3, but not
soluble in EtOH, MeOH, MeCN, acetone, THF, ethyl
acetate or n-hexane. Noticeably, they are both unstable in
air at room temperature. The free ligand is soluble in all
of the aforementioned solvents. The molar conductance
values of complexes 1 and 2 in 1.0 9 10-3 mol dm-3 DMF
solutions are 15.5 and 15.2 S cm2 mol-1, respectively,
indicating that both are non-electrolytes. This implies that
all of the acetate groups in both complexes are held in the
coordination sphere in solution or solid state.
1
crystalline solid (Yield 481 mg, 63%, M.P. 97–98 °C). H
NMR (400 MHz, CDCl3) 2.12 (t, J = 6.6 Hz, 2H), 3.81 (s,
6H), 4.26 (t, J = 6.20 Hz, 4H), 6.46 (d, J = 2.4 Hz 2H),
6.50 (d, J = 2.4 Hz 2H), 6.98 (s, 2H), 8.09 (s, 2H), 10.00 (s,
2H). Found: C, 61.0; H, 6.0; N, 7.3. Calcd. for C19H22N2O6
(%): C, 61.0; H, 5.9; N, 7.5.
Preparation of complex 1
A solution of Co(OAc)2ꢀ4H2O (8.0 mg, 0.032 mmol) in
methanol (4 mL) was added dropwise to a solution of
H2L (12.1 mg, 0.032 mmol) in acetonitrile (4 mL). The
color of the solution immediately turned yellow, and
the mixture was allowed to stand at room temperature
for about 1 week. After the solvent was partially
evaporated, it separated out several reddish-brown
block-shaped single crystals suitable for X-ray crystal-
lographic analysis. Found: C, 48.1; H, 5.5; N, 6.6; Co,
14.1. Calcd. for C50H68Co3N6O20 (%): C, 48.1; H, 5.5;
N, 6.7; Co, 14.2.
Principal FTIR bands for H2L and its complexes 1 and 2
are given in Table 2. The free ligand H2L exhibits Ar–O
and C=N stretching bands at 1,223 and 1,613 cm-1, which
are shifted to lower frequencies by ca. 2 and 7 cm-1 for
complex 1 (4 and 2 cm-1 for complex 2) upon complex-
ation. This lowering of energy results from the Co–O and
Co–N interactions upon complexation and is similar to that
reported for other CoII complexes [17]. In addition, the
123

Transition Met Chem (2010) 35:787–794
789
Table 1 Crystal data and structure refinement parameters for complexes 1 and 2
Complex
1
2
Empirical formula
Formula weight (g mol-1
Crystal system
C50H68Co3N6O20
C52H76Co3N4O21
1269.96
)
1249.89
Monoclinic
Tꢁriclinic
Space group
C2/c
P
1
Temperature (K)
˚
153(2) K
298(2) K
Unit cell dimensions(A, °)
a = 25.1482(7)
a = 11.476(1)
b = 11.901(1)
c = 11.965(1)
a = 70.911(1)
b = 72.603(1)
c = 86.811(2)
1472.0(2)
b = 12.3318(5)
c = 19.8322(6)
a = 90
b = 115.801(1)
c = 90
3
˚
V (A )
5537.3(3)
Z
4
1
Calculated density (mg/m3)
Absorption coefficient (mm-1
h range for data collection (°)
Limiting indices
1.499
1.433
)
0.969
0.913
3.14–27.48
1.81–25.02
-32 B h B 30, -15 B k B 16, -24 B l B 25
-13 B h B 13, -11 B k B 14, -9 B l B 14
665
F(000)
2,604
Crystal size (mm)
0.58 9 0.57 9 0.37
41,875/6,326 [R(int) = 0.0376]
Full-matrix least squares on F2
6,326/0/373
0.38 9 0.28 9 0.27
7,706/5,120 [R(int) = 0.0177]
Full-matrix least squares on F2
5,120/0/429
Reflection collected/unique
Refinement method
Data/restraints/parameters
Goodness of fit on F2
Final R indices [I [ 2r(I)]
R indices (all data)
1.020
1.005
R1 = 0.0332, wR2 = 0.0862a
R1 = 0.0368, wR2 = 0.0897
0.7157 and 0.6033
652641
R1 = 0.0370, wR2 = 0.0908b
R1 = 0.0572, wR2 = 0.1053
0.7907 and 0.7230
-3
)
˚
Max, min Dq (eA
CCDC
751664
a
b
w = 1/[r2(Fo2) ? (0.0483P)2 ? 9.1774P], w = 1/[r2(Fo2) ? (0.0472P)2 ? 0.7277P], where P = (Fo2 ? 2F2c)/3
Scheme 1 Synthesis of the
complexes, R = Me (1) or
Et (2)
MeO
OMe
OMe
O
O
O
O
O
N O
O
N
OH
OH
O N
R
Co(OAc)2·4H2O
MeCN/ROH
H
Co
O
Co
O
Co
O
H
R
O
N
O
N
O
O N
O
OMe
OMe
MeO
infrared spectra of complexes 1 and 2 show the expected
absorption band due to the stretching modes of methanol or
ethanol at ca. 3,432 and 3,425 cm-1, respectively.
Table 2 Principal FTIR bands for H2L and complexes 1 and 2
(cm-1
)
Compound m(Ar–O) m(C=N) m(Co–N) m(Co–O) m(C=C) benzene
ring skeleton
The far-infrared spectra of complexes 1 and 2 were also
obtained in the region of 500–100 cm-1. The IR spectrum
of complex 1 shows m(Co–O) and m(Co–N) vibrations at
411 and 473 cm-1, respectively (413 and 474 cm-1 for
complex 2), which are consistent with the literature values
H2L
1,223 1,613
–
–
1,570, 1,514, 1,460
1,539, 1,491, 1,418
1,585, 1,535, 1,450
Complex 1 1,221 1,606 473
Complex 2 1,219 1,611 474
411
413
123

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Transition Met Chem (2010) 35:787–794
Description of the crystal structures
[18–20]. Analogous bands are not observed in the spectrum
of the free ligand. As pointed out by Percy and Thornton
[21], the precise metal–oxygen and metal–nitrogen
assignments are often difficult.
In order to determine the correct configuration of the
complexes, X-ray crystallographic studies have been real-
ized for complexes 1 and 2. Complex 1 crystallizes in the
monoclinic space group C2/c, and consists of two
L2- ligands, three CoII atoms, two acetate anions, two
coordinated methanol molecules, two non-coordinated
methanol and two non-coordinated acetonitrile molecules.
Selected bond lengths and angles are listed in Table 3.
As shown in Fig. 1, the two terminal CoII atoms (Co1
and Co1#1) are both located in the cis-N2O2 coordination
cavity of the L2- ligands, and carboxylate oxygen atom O7
from the l-acetato bridge and oxygen atom O9 from the
methanol ligand are also coordinated to Co1 in the axial
positions. Furthermore, the dihedral angle between the
coordination planes of O1–Co1–N1 and O2–Co1–N2 is
4.50(2)°, indicating slight distortion toward octahedral
geometry from the square planar structure. Because Co1
and Co1#1 are symmetry related, they will have identical
geometries [26]. In addition, the coordination sphere of
the central CoII atoms (Co2) is completed by quadruple
The UV–Vis absorption spectrum of H2L in DMF
solution exhibits two intense peaks at around 278 and
311 nm. These are the characteristic peaks for any Salen-
type ligands due to p–p* transitions [22, 24]. However,
there is no absorption around 400 nm, which is usually
seen for Salen derivatives in the keto-NH form [23, 25].
The absorption peak of H2L at 278 nm is shifted to
lower energy by ca. 13 and 5 nm in complexes 1 and 2,
respectively, consistent with coordination of the CoII atoms
to L2- ligands. The peak of H2L at 311 nm is absent for
complexes 1 and 2. However, new absorptions are
observed at 339 and 346 nm, respectively, and assigned
to be the n - p* charge transfer transition from the filled
pp orbital of the bridging phenolic oxygen to the vacant
d-orbital of the CoII atoms [24].
The thermal decomposition of complex 1 can be divided
into four stages. The first stage is at 45–67 °C. The TG
curve shows that the weight loss corresponding to this
temperature range is 11.1%, which roughly coincides with
the value of 11.7%, calculated for the loss of non-coordi-
nated solvent (two of methanol and two of acetonitrile)
from complex 1. The second stage starts from 84 to 97 °C
with a weight loss of 4.8%, which corresponds to the loss
of two methanol ligands (theoretical mass loss 5.1%). The
third stage degradation is in the range of 216–252 °C with
a mass loss of 10.2%, assigned to loss of two coordinated
acetate groups with theoretical value of 9.4%. The residue
remains stable up to 334 °C, when the fourth weight loss
starts. The TG curve shows around 79% total mass loss at
800 °C, indicating complete removal of the organic part of
the compound. The residue was CoO with a value of 21%
(theoretical value 18.0%).
˚
Table 3 Selected bond distances (A) and bond angles (°) for
complex 1
Bond lengths
Co(1)–O(7)
2.051(1)
2.055(1)
2.076(1)
2.138(1)
2.138(2)
2.142(2)
Co(2)–O(2)
Co(2)–O(2)#1
Co(2)–O(1)
Co(2)–O(1)#1
Co(2)–O(8)
Co(2)–O(8)#1
2.076(1)
2.076(1)
2.120(1)
2.120(1)
2.146(1)
2.146(1)
Co(1)–O(1)
Co(1)–O(2)
Co(1)–O(9)
Co(1)–N(2)
Co(1)–N(1)
Bond angles
O(7)–Co(1)–O(1)
O(7)–Co(1)–O(2)
O(1)–Co(1)–O(2)
O(7)–Co(1)–O(9)
O(1)–Co(1)–O(9)
O(2)–Co(1)–O(9)
O(7)–Co(1)–N(2)
O(1)–Co(1)–N(2)
O(2)–Co(1)–N(2)
O(9)–Co(1)–N(2)
O(7)–Co(1)–N(1)
O(1)–Co(1)–N(1)
O(2)–Co(1)–N(1)
O(9)–Co(1)–N(1)
N(2)–Co(1)–N(1)
93.46(5)
92.01(5)
78.63(5)
173.07(5)
93.38(5)
88.29(5)
87.60(6)
164.77(5)
86.15(5)
85.51(6)
93.29(6)
84.85(5)
162.92(5)
88.40(5)
110.28(6)
O(2)–Co(2)–O(2)#1
O(2)–Co(2)–O(1)
180.00(6)
77.18(5)
102.82(5)
102.82(5)
77.18(5)
180.00(1)
90.05(5)
89.95(5)
87.48(4)
92.52(4)
89.95(5)
90.05(5)
92.52(4)
87.48(4)
180.0
Thermal decomposition of complex 2 also occurs in four
stages. The initial weight loss occurs in the range
45–53 °C. The TG curve shows that weight loss corre-
sponding to this temperature range is 10.3%, consistent
with 10.9% calculated for loss of three non-coordinated
ethanol molecules. The second stage is 88–102 °C with
weight loss of 7.0%, assigned to the loss of two ethanol
ligands (theoretical mass loss, 7.3%). The third stage of
degradation is in the range 216–252 °C with mass loss of
9.8%, in which two coordinated acetate anions are lost with
theoretical value of 9.3%. The solid remains stable up to
348 °C, whereupon fourth weight loss commences. Sub-
sequently, continuous mass loss was observed up to
800 °C. At this temperature, CoO is formed. The total mass
loss found (82.3%) was consistent with the calculated value
(82.3%).
O(2)#1–Co(2)–O(1)
O(2)–Co(2)–O(1)#1
O(2)#1–Co(2)–O(1)#1
O(1)–Co(2)–O(1)#1
O(2)–Co(2)–O(8)
O(2)#1–Co(2)–O(8)
O(1)–Co(2)–O(8)
O(1)#1–Co(2)–O(8)
O(2)–Co(2)–O(8)#1
O(2)#1–Co(2)–O(8)#1
O(1)–Co(2)–O(8)#1
O(1)#1–Co(2)–O(8)#1
O(8)–Co(2)–O(8)#1
Symmetry transformations used to generate equivalent atoms:
#1-x ? 3/2, -y ? 3/2, -z ? 1
123

Transition Met Chem (2010) 35:787–794
791
Fig. 1 ORTEP view of the
crystal structure of complex 1.
Thermal ellipsoids were drawn
at the 30% probability level and
hydrogen atoms have been
omitted for clarity
l-phenoxo oxygen atoms from two L2- moieties and
double l-acetato oxygen atoms which adopt a familiar l–
O–C–O fashion. All the six oxygen atoms coordinated to
Co2 constitute an octahedral geometry: one acetate anion
serves as bridging group for Co1 and Co2 and the other
coordinates to Co1#1 and Co2, in both cases via Co–O–C–
O–Co bridges. The Co1(or Co1#1) atom in complex 1 is
that the terminal CoII center has a higher distortion than
that of the central one in octahedral geometry.
There is an inversion center through the central CoII
˚
atom (Co2), and the distance of Co2–O1 (2.1198(1) A) is
˚
longer than that of Co2–O2 (2.076(1) A) (Table 3), indi-
cating a weaker steric effect. Similar elongations of Co–O
bonds have also been observed in the [Co(Salen)]2 dimer
˚
˚
[17]. The Co1–N2 (2.1422(2) A) is slightly longer than
0.052 A out of the N2O2 coordination plane defined by
atoms (N1N2O1O2 or N1#1N2#1O1#1O2#1), while the Co2
atom lies exactly in the corresponding N2O2 coordination
plane defined by atoms (O1O2O1#1O2#1). The bond angles
around Co1 or Co1#1 in the trans-positions are in the range
of 162–173°, while those around Co2 are all 180°, showing
Co1–N1 (2.1384(2) A), which is attributed to the methanol
˚
molecule coordinating to the terminal CoII atoms (Co1 and
Co1#1) resulting in larger steric hindrance.
In the crystal structure of complex 1, as shown in Fig. 2,
each of two non-coordinated methanol molecules is con-
nected with the two non-coordinated acetonitrile molecules
through C25–H25AꢀꢀꢀO10 hydrogen-bonding interactions
(Table 4). Also, the non-coordinated methanol molecules
are linked to the inner-sphere units, {[CoL(MeOH)(l-
OAc)]2Co}, via O10–H10ꢀꢀꢀO8, O9–H9ꢀꢀꢀO10 and C23–
H23Cꢀꢀꢀp hydrogen-bonding interactions, and to form a
monomer structure of {[CoL(MeOH)(l-OAc)]2Co}ꢀ2MeCNꢀ
2MeOH units. Furthermore, every monomer molecule links
four other molecules into an infinite 2D-layer supramolec-
ular structure parallel to the bc crystallographic plane via
intermolecular hydrogen bonds between the oxygen atoms of
the methoxy group and the methylene groups of O-alkyl
chains of L2- ligands in the adjacent molecules (Fig. 3).
The molecular structure of complex 2 is shown in Fig. 4.
Selected bond lengths and angles are given in Table 5.
Cꢁomplex 2 crystallizes in the triclinic system, space group
P
with a linear trinuclear array of three CoII atoms
1
Fig. 2 Hydrogen-bonding interactions of complex 1
123

792
Transition Met Chem (2010) 35:787–794
˚
Table 4 Hydrogen-bonding distances (A) and bond angles (°) for
complexes 1 and 2
D–HꢀꢀꢀA
D–H
HꢀꢀꢀA
DꢀꢀꢀA
D–HꢀꢀꢀA
Complex 1
O9–H9ꢀꢀꢀO10
0.85
0.82
0.98
0.98
0.99
0.99
1.77
1.86
2.46
2.89
2.69
2.63
2.616 (2)
2.680(2)
3.419(3)
3.784(2)
3.473(2)
3.498(4)
177
175
166
153
137
147
O10–H10OꢀꢀꢀO8i
C25–H25AꢀꢀꢀO10ii
C23–H23CꢀꢀꢀCg1
C8–H8AꢀꢀꢀO6iii
C9–H9AꢀꢀꢀO5iv
Complex 2
O9–H9ꢀꢀꢀO10v
O10–H10ꢀꢀꢀO8
C24–H24BꢀꢀꢀCg2vi
C2–H2AꢀꢀꢀO6vii
C2–H2BꢀꢀꢀO2viii
0.82
0.82
0.97
0.97
0.97
1.825
1.945
2.71
2.641(3)
2.761(3)
3.614(5)
3.339(5)
3.548(4)
173
174
156
135
156
2.58
2.64
Symmetry codes: (i) 3/2 - x, 3/2 - y, 1 - z; (ii) 1 - x, y, ‘ - z;
(iii) x, 2 - y, 1/2 ? z; (iv) x, 1 - y, 1/2 ? z; (v) 1 - x, 1 - y, 1 - z;
(vi) 1 - x, 1 - y, 1 - z; (vii) 1 ? x, y, z; (viii) 2 - x, 2 - y,
-z. Cg1 and Cg2 are the centroids of atoms C1–C6 and C13–C18,
respectively
Fig. 4 ORTEP view of the crystal structure of complex 2. Thermal
ellipsoids were drawn at the 30% probability level and hydrogen
atoms have been omitted for clarity
coupled by both doubly l-phenoxo oxygen atoms of L2-
ligands plus two acetate anions in the syn–syn bridging
mode. All the hexa-coordinated CoII atoms of complex
positions around the terminal CoII centers is not from the
methanol but the ethanol ligand in complex 2. The dihedral
angle between the planes of O5–Co1–N2 and O3–Co1–N1 in
complex 2 is 7.96(4)°, which is a little bigger than that of
O1–Co1–N1 and O2–Co1–N2 (4.50(2)°) in complex 1.
Furthermore, the terminal atom (Co1 and Co1#1) in complex
2 have a slightly distorted octahedral coordinated
polyhedron.
The structure of complex 2 is pseudo isostructural with
that of complex 1. Consequently their structural features are
very similar except that one of the oxygen atoms in apical
˚
2 is 0.062 A out of the N2O2 coordination equatorial plane
Fig. 3 View of the 2D
supramolecular network of
complex 1 (hydrogen atoms,
except those forming hydrogen
bonds, are omitted for clarity)
123

Transition Met Chem (2010) 35:787–794
793
˚
atom has a higher distortion than the central one in octahedral
geometry in both complexes. Furthermore, the distortion
around the terminal CoII atoms in complex 2 is stronger than
that in complex 1, perhaps due to larger steric hindrance of
the ethanol ligands compared to the methanol ligands.
In addition, similar to complex 1, analysis of the crystal
packing of 2 shows a 2D hydrogen-bonding supramolecu-
lar network involving intermolecular O10–H10ꢀꢀꢀO8, O9–
H9ꢀꢀꢀO10 and C24–H24Bꢀꢀꢀp(Ph, C13–C18) interactions
(Fig. 5). Moreover, the monomers are linked by intermo-
lecular C2–H2AꢀꢀꢀO6 and C2–H2BꢀꢀꢀO2 hydrogen bond
interactions into a 2D supramolecular network structure
(Fig. 6).
Table 5 Selected bond distances (A) and bond angles (°) for com-
plex 2
Bond lengths
Co(1)–O(3)
Co(1)–O(7)
Co(1)–O(5)
Co(1)–N(1)
Co(1)–N(2)
Co(1)–O(9)
Bond angles
2.039(2)
2.054(2)
2.074(2)
2.127(3)
2.135(3)
2.159(2)
Co(2)–O(3)
Co(2)–O(3)#1
Co(2)–O(5)#1
Co(2)–O(5)
Co(2)–O(8)
Co(2)–O(8)#1
2.097(2)
2.097(2)
2.098(2)
2.098(2)
2.141(2)
2.141(2)
O(3)–Co(1)–O(7) 95.59(8)
O(3)–Co(1)–O(5) 78.98(7)
O(7)–Co(1)–O(5) 90.71(8)
O(3)–Co(1)–N(1) 86.22(9)
O(7)–Co(1)–N(1) 88.7(1)
O(3)–Co(2)–O(3)#1
O(3)–Co(2)–O(5)#1
O(3)#1–Co(2)–O(5)#1 77.13(8)
180.000(1)
102.87(7)
O(3)–Co(2)–O(5)
O(3)#1–Co(2)–O(5)
O(5)–Co(1)–N(1) 165.05(9) O(5)#1–Co(2)–O(5)
77.13(8)
102.87(7)
180.00(7)
88.43(8)
91.57(8)
91.90(8)
88.10(8)
91.57(8)
Solvent effects
For both complexes 1 and 2, the ratio of L:Co is 2:3. Every
terminal CoII atom forms two six-membered rings with two
salicylaldoxime moieties and the acetates adopt their
familiar role to reinforce the structures by bridging
between adjacent CoII atoms. The influence of solvent
effect is clearly revealed in selected bond distances and
angles for complexes 1 and 2. In complex 1, the distance
from O9 (coordinated methanol molecule) to the plane of
O(3)–Co(1)–N(2) 162.21(9) O(3)–Co(2)–O(8)
O(7)–Co(1)–N(2) 92.6(1)
O(5)–Co(1)–N(2) 85.15(9)
N(1)–Co(1)–N(2) 109.8(1)
O(3)–Co(1)–O(9) 86.51(9)
O(3)#1–Co(2)–O(8)
O(5)#1–Co(2)–O(8)
O(5)–Co(2)–O(8)
O(3)–Co(2)–O(8)#1
O(7)–Co(1)–O(9) 176.77(8) O(3)#1–Co(2)–O(8)#1 88.43(8)
O(5)–Co(1)–O(9) 92.11(9)
N(1)–Co(1)–O(9) 89.0(1)
N(2)–Co(1)–O(9) 86.1(1)
O(5)#1–Co(2)–O(8)#1 88.10(8)
O(5)–Co(2)–O(8)#1
O(8)–Co(2)–O(8)#1
91.90(7)
180.0(1)
˚
˚
N1–N2–O1–O2 is 2.081(2) A and O9–Co1 is 2.138(1) A,
so we confirm that Co1 is not coplanar with the N1–N2–
O1–O2 plane and slightly deviates toward O7 from the
acetate anion. The dihedral angle between N1–Co1–O1 and
N2–Co1–O2 is 4.50(2)°. Complex 2 shows that the dis-
tance from O9 (ethanol ligand) to the plane of N1–N2–O3–
Symmetry transformations used to generate equivalent atoms:
#1-x ? 1, -y ? 1, -z ? 1
˚
(that of in complex 1 is 0.052 A), but the central Co2 atom
˚
˚
lies in the corresponding O2O2 equatorial plane. The bond
angles around Co1 or Co1#1 in the trans-positions are in the
range of 162–177° in complex 2, whereas those of complex 1
are in the range of 162–173°, showing that the terminal CoII
O5 (2.96(2) A) is shorter than O9–Co1 (2.159(2) A). As
for complex 1, Co1 is also not coplanar with the N1–N2–
O3–O5 plane but slightly deviates toward O7 from the
acetate anion. The dihedral angle between N1–Co1–O3 and
N2–Co1–O5 is 7.96(4)°. This deviation of Co1 toward O7
in both complexes may be attributed to the electrostatic
attraction of acetate. Further, the dihedral angle of the two
planes (N1–Co1–O3 and N2–Co1–O5) in complex 2
(7.96(4)°) is bigger than that in complex 1 (4.50(2)°), due
to larger steric hindrance of the ethanol ligands than the
methanol ligands. Thus, solvent effects in complexes 1 and
2 can explain their slight differences in crystal structures
(Scheme 1).
Conclusion
Two trinuclear CoII complexes have been synthesized and
characterized. Because of the introduction of different
solvent molecules, these complexes present slightly dif-
ferent structural features. Complex 1 has two methanol
ligands coordinated to the terminal CoII atoms, while
complex 2 has ethanol ligands. The distortion of the
Fig. 5 Hydrogen-bonding interactions of complex 2
123

794
Transition Met Chem (2010) 35:787–794
Fig. 6 View of the 2D
supramolecular network of
complex 2 (hydrogen atoms,
except those forming hydrogen
bonds, are omitted for clarity)
octahedral coordination geometry around the terminal CoII
atoms in complex 2 is stronger than that of complex 1,
suggesting that the steric hindrance of the ethanol ligands is
larger than that of the methanol ligands.
6. Eddaoudi M, Moler DB, Li H, Chen B, Reineke TM, O’Keeffe
M, Yaghi OM (2001) Acc Chem Res 34:319–330
7. Chen B, Eddaoudi M, Hyde ST, O’Keeffe M, Yaghi OM (2001)
Science 291:1021–1023
8. Kim J, Chen B, Reineke TM, Li H, Eddaoudi M, Moler DB,
O’Keeffe M, Yaghi OM (2001)
8239–8247
J Am Chem Soc 123:
9. Yaghi OM, O’Keeffe M, Ockwig NW, Chae HK, Eddaoudi M,
Kim J (2003) Nature 423:705–741
Supplementary material
10. Forster PM, Cheetham AK (2004) Microporous Mesoporous
Mater 73:57–64
Crystallographic data have been deposited with the Cam-
bridge Crystallographic Data Centre as supplementary
publication, No. CCDC 652641 and 751664 for complexes 1
and 2, respectively. Copies of the data can be obtained free of
charge on application to CCDC, 12 Union Road, Cambridge
CB2 1EZ, UK (Telephone: ?44-01223-762910; Fax: ?44-
1223-336033; E-mail: deposit @ccdc.cam.ac.uk). These
data can be also obtained free of charge at www.ccdc.cam.
ac.uk/conts/retrieving.html.
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45:4677–4684
T (2006) Inorg Chem
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Inorg Met-Org Nano-Met Chem 37:61–67
13. Dong WK, Feng JH, Yang XQ (2007) Synth React Inorg Met-Org
Nano-Met Chem 37:189–192
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corrected software. University of Gottingen, Germany
16. Sheldrick GM (1997) SHELXTL NT, version 5.1; program for
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Gottingen, Germany
Acknowledgments This work was supported by the Foundation of
the Education Department of Gansu Province (No. 0904-11) and the
‘JingLan’ Talent Engineering Funds of Lanzhou Jiaotong University,
which are gratefully acknowledged.
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