Synthesis, structure and properties of supramolecular MnII, CoII, NiIIand ZnII complexes containing Salen-type bisoxime ligands

Article abstract of DOI:10.1016/j.poly.2010.04.006

Four supramolecular complexes [MnL¹(H₂O)₂] (1), {[CoL²(OAc)(H₂O)]₂Co)·5CH ₃CH₂OH (2), {[NiL³(OAc)-(CH₃OH)] ₂Ni}·2CH₃COCH

Full text of DOI:10.1016/j.poly.2010.04.006

Polyhedron 29 (2010) 2087–2097
Contents lists available at ScienceDirect
Polyhedron
journal homepage: www.elsevier.com/locate/poly
Synthesis, structure and properties of supramolecular MnII, CoII, NiII and ZnII
complexes containing Salen-type bisoxime ligands
*
Wen-Kui Dong , Yin-Xia Sun, Chun-Yu Zhao, Xiu-Yan Dong, Li Xu
School of Chemical and Biological Engineering, Lanzhou Jiaotong University, Lanzhou 730070, PR China
a r t i c l e i n f o
a b s t r a c t
Four supramolecular complexes [MnL1(H2O)2] (1), {[CoL2(OAc)(H2O)]2Co}Á5CH3CH2OH (2), {[NiL3(OAc)-
(CH3OH)]2Ni}Á2CH3COCH3Á2CH3OH (3) and {[ZnL2(OAc)]2Zn}ÁCHCl3 (4), have been synthesized and char-
acterized by elemental analyses, IR, UV–Vis spectra and X-ray diffraction techniques. All the complexes
have the trinuclear configuration except for MnII complex being mononuclear configuration. Every trinu-
clear complex contains two acetate ions coordinate to the three metal ions via a familiar M–O–C–O–M
(M = Co, Ni, Zn) coordinated mode. Although complexes 1 and 3 display 1D supramolecular chains, the
different coordination environments (mononuclear in 1, trinuclear in 3) provoke divergence in the struc-
tures and aggregations of the chain subunits. Complex 2 forms a 3D hydrogen-bonding supramolecular
networks possessing a channel composing of six O–HÁÁÁO hydrogen bonds, while complex 4 exhibits a
2D hydrogen-bonding supramolecular networks with the formation of ‘‘grottos” occupied by chloroform
molecules through intermolecular hydrogen-bond interactions. The spectral properties of the title com-
plexes have been further discussed in detail.
Article history:
Received 4 December 2009
Accepted 5 April 2010
Available online 14 April 2010
Keywords:
Salen-type bisoxime ligand
Synthesis
Complex
Supramolecular structure
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
esting characteristics: they can provide N and O donor sites to
coordinate with metal atoms, and the presence of O and N atoms
The self-assembly and investigating synthetic routes have been
developed maturely in the field of metal–organic complexes or
supramolecular architectures [1]. And the development of
metal–organic complex would be allowed to design new topolo-
gies of functional materials, in which pore size, coordination forms
and functionality could be varied in large scale [2]. Recently a sig-
nificant increase in the research of coordination supramolecules in
which metal ion centers are bridged through organic molecules has
been observed because of their enormous variety of intriguing
structural topologies and their fascinating properties as well as
great potential applications in optoelectronics, magnetism, and
catalysis [3–10]. This subject is currently being pursued in our re-
search, including functional oxime groups and metal atoms with
magnetism, photoelectricity and catalysis.
To generate target complexes by design, a judicious choice of
ligands provides a way of controlling supramolecular interactions.
In general, ligands with certain features, such as rigidity and
symmetry, are suitable for obtaining coordination supramolecules.
In order to optimize the properties and explore the varied possibil-
ities of transition metal coordination supramolecules, we have
explored Salen-type bisoxime ligands (Scheme 1) with the inter-
and aromatic rings may form hydrogen bonds and
p–p stacking
interactions to extend and stabilize the whole framework series.
Hence, diverse supramolecular structures may result from these
interesting ligands.
Here, we selected three Salen-type bisoxime ligands for the de-
sign of the new coordinated supramolecule with oxime resulting in
four new complexes: [MnL1(H2O)2] (1), {[CoL2(OAc)(H2O)]2Co}Á
5CH3CH2OH (2), {[NiL3(OAc)(CH3OH)]2Ni}Á2CH3COCH3Á2CH3OH
(3) and {[ZnL2(OAc)]2Zn}ÁCHCl3 (4). The structures 1 and 3 consist
of a chain with hydrogen bonding or
p–p stacking interactions,
while 2 is self-assembled to a three-dimensional networks with
channels composing of hydrogen bonds, and 4 exhibits a two-
dimensional networks with ‘‘grottos” occupied by chloroform mol-
ecules. To our knowledge, the two- or three-dimensional transition
metal networks assembled motifs with ‘‘grottos” or channels are
uncommon.
2. Experimental
2.1. Materials and instruments
C, H, N elemental analyses were performed with a GmbH Vari-
oEL V3.00 automatic elemental analysis instrument. Elemental
analyses for Mn, Zn, Co and Ni were detected by an IRIS ER/
SÁWP-1 ICP atomic emission spectrometer. Molar conductance
* Corresponding author. Tel.: +86 931 4938703; fax: +86 931 4956512.
E-mail address: dongwk@126.com (W.-K. Dong).
0277-5387/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2010.04.006

2088
W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
O
C
O
C
O
C
(
)
n
(
)
Br
Br
n
NH2NH`H2O
O
N
N
O
N
OH
O
NH2
H2N
O
C
O
C
O
C
O
CHO
OH
(
)
2
n
n=1, R1 = R2 = Br, ligand = H2L1
n=1, R1 = H, R2 = Br, ligand = H2L2
n=2, R1 = H, R2 = Br, ligand = H2L3
O
O
N
R1
R2
N
R2
R2
HO
OH
R1
R1
Scheme 1. The synthesis route of the ligands: H2L1, H2L2 and H2L3.
value measurements were carried out on a model DDS-11D type
conductivity bridge using 1.0 Â 10À3 mol dmÀ3 solution in DMF
at 18 °C. Melting points were obtained by the use of a microscopic
melting point apparatus made in Beijing Taike Instrument Limited
Company and were uncorrected. IR spectra were recorded on a
VERTEX70 FT-IR spectrophotometer, with samples prepared as
KBr (500–4000 cmÀ1) and CsI (100–500 cmÀ1) pellets. 1H NMR
spectra were determined by German Bruker AVANCE DRX-400
spectroscopy. The electronic spectra were recorded with a RF-
540 spectrophotometer in diluted DMF solution. Fluorescence
measurements were made with a Hitachi F-4500 spectrophotome-
ter and a shimadzu RF-540 spectrofluorophotometer equipped
with quartz cuvettes of 1 cm path length. An excitation slit of
2.5 nm and an emission slit of 2.5 nm were used for the
measurements.
2.2. Synthesis of ligands H2L1, H2L2 and H2L3
5-Bromosalicylaldehyde and 3,5-dibromosalicylaldehyde from
Alfa Aesar were used without further purification. 1,2-Dibromo-
ethane and 1,3-dibromopropane were dried and redistilled before
use. 1,2-Bis(aminooxy)ethane and 1,3-bis(aminooxy)propane were
synthesized according to an analogous method reported earlier
[11]. The other reagents and solvents were of analytical reagent
grade and were used without further purification. The ligands
H2L1, H2L2 and H2L3 have been prepared according to a literature
procedure [12,13]. H2L1: yield 479.1 mg (78.6%); m.p. 189–
190 °C. 1H NMR (400 MHz, DMSO-d6, d, ppm) 4.49 (s, 4H, CH2),
7.68 (d, J = 2.4 Hz, 2H, Ar–H), 7.82 (d, J = 2.4 Hz, 2H, Ar–H), 8.47
(s, 2H, @C–H), 10.43 (s, 2H, OH). IR (KBr, cmÀ1): 3078(w)
m
(C–H
arom); 2936(w), 2872(w)
m
(C–H); 1603(m) m(C@N oxime);
Table 1
Crystallographic data, data collection and structure refinement for the obtained crystals.
Complex
1
2
3
4
CCDC
696151
696146
696133
696150
Empirical formula
Formula weight
Crystal system
Space group
Unit cell dimensions
a (Å)
C16H14Br4MnN2O6
704.87
monoclinic
C2/c
C46H64Br4Co3N4O19
1473.44
triclinic
C48H62Br4N4Ni3O18
1478.79
triclinic
C37H31Br4Cl3N4O12Zn3
1345.76
monoclinic
Pn
ꢀ
ꢀ
P1
P1
17.574(3)
15.181(2)
7.9451(16)
90.00
96.520(2)
90.00
2106.0(6)
4
2.223
10.8568(9)
12.3018(13)
12.3023(13)
87.379(2)
74.8090(10)
65.8710(10)
1443.6(2)
1
9.7769(10)
11.9802(12)
12.9019(14)
92.3930(10)
94.486(2)
94.048(2)
1501.1(3)
1
10.6045(14)
9.1876(12)
24.997(3)
90
92.755(2)
90
2432.6(5)
2
1.837
b (Å)
c (Å)
a
(°)
b (°)
c
(°)
V (Å3)
Z
Dc (Mg mÀ3
)
1.695
3.692
1.636
3.662
l(Mo K
a
) (mmÀ1
)
8.252
4.976
F(0 0 0)
1348
741
746
1316
Crystal size (mm)
h for data collection (°)
Index ranges
0.42 Â 0.18 Â 0.17
1.78–25.00
À17 6 h 6 20,
À18 6 k 6 17,
À9 6 l 6 9
5096
0.19 Â 0.18 Â 0.17
1.72–25.01
À12 6 h 6 11,
À14 6 k 6 12,
À14 6 l 6 14
7489
0.40 Â 0.35 Â 0.29
1.58–25.00
À11 6 h 6 11,
À14 6 k 6 14,
À15 6 l 6 12
7405
0.40 Â 0.39 Â 0.37
1.63–25.01
À12 6 h 6 12,
À10 6 k 6 10,
À14 6 l 6 29
11 672
Reflections collected
Independent reflections
Rint
1805
0.0520
4992
0.0232
5087
0.0316
5643
0.0772
Completeness to h = 25.00 (%)
Data/restraints/parameters
Goodness-of-fit (GOF) on F2
R1
97.1
1805/0/132
1.029
98.2
4992/0/361
1.020
95.9
5087/1/354
1.012
99.6
5643/2/569
1.054
0.0453
0.0459
0.0447
0.0826
wR2 [I > 2
D
r
(I)]
0.1084
1.773 and À0.484
0.1180
1.355 and À0.613
0.1183
0.649 and À1.049
0.1956
1.388 and À1.523
qmax,min (e ÅÀ3
)

W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
2089
1271(m)
m
(C–O). Anal. Calc. for C16H12N2O4Br4 (%): C, 31.20; H,
[MnL1(H2O)2]: C, 27.35; H, 2.03; N, 3.97; Mn, 7.83. Found: C,
27.26; H, 2.00; N, 3.95; Mn, 7.81%. IR (KBr, cmÀ1): 3073(w)
(C–
H arom); 2951(w), 2889(w) (C–H); 1601(m) (C@N oxime);
1308(m) (C–O).
1.96; N, 4.55. Found: C, 31.18; H, 1.98; N, 4.54%. The data of H2L2
and H2L3 have been reported previously [12,13].
m
m
m
m
2.3. Synthesis of complexes 1–4
2.3.2. Complexes 2 and 4
A solution of cobalt acetate tetrahydrate (or zinc acetate dihy-
drate) (0.10 mmol) in ethanol (20 ml) was added dropwise to a
solution of H2L2 (0.10 mmol) in acetone (or chloroform) (20 ml) at
room temperature. The mixture was stirred at room temperature
for 4 h, and the solution was filtered. Upon standing the filtrate at
room temperature for several weeks, single crystals suitable for
X-ray crystallographic analysis were obtained, respectively. The
elemental analyses showed that the metal complexes obtained
were composed of a 3:2 ratio of MII to ligand. This ratio was later
unequivocally confirmed by X-ray crystallographic analyses. Data
for {[CoL2(OAc)(H2O)]2Co}Á5CH3CH2OH (2), C46H64Br4Co3N4O19
(1473.44): yield, 35.7%. Anal. Calc. for {[CoL2(OAc)(H2O)]2Co}Á
5CH3CH2OH: C, 37.48; H, 4.35; N, 3.82; Co, 12.02. Found: C,
2.3.1. Complex 1
A solution of MnII acetate tetrahydrate (0.05 mmol) in methanol
(15 ml) was added dropwise to a solution of H2L1 (0.05 mmol) in
THF (45 ml) at room temperature. After continuing stirring for
2 days at room temperature, the mixture was filtered and the fil-
trate was allowed to stand at room temperature for several weeks.
Then the yellow needle-like single crystals suitable for X-ray crys-
tallographic analysis were obtained. The elemental analyses
showed that the metal complexes obtained are composed of a
1:1 ratio of MII to ligand. This ratio was later unequivocally con-
firmed by X-ray crystallographic analyses. Data for [MnL1(H2O)2]
(1), C16H14Br4MnN2O6 (704.87): Yield: 41.6%. Anal. Calc. for
37.50; H, 4.38; N, 3.80; Co, 12.00%. IR (KBr, cmÀ1): 3364(vw)
m(O–
H); 3074(w)
m(C–H arom); 2918(w), 2872(w) m(C–H); 1610(m)
O
N
O
N
m(C@N oxime); 1250(m)
m
(C–O). Data for {[ZnL2(OAc)]2Zn}ÁCHCl3
OH2
Mn
Br
Br
(4), C37H31Br4Cl3N4O12Zn3 (1345.76): Yield, 42.6%. Anal. Calc. for
{[ZnL2(OAc)]2Zn}ÁCHCl3: C, 33.01; H, 2.34; N, 4.13; Zn, 14.58. Found:
C, 33.02; H, 2.32; N, 4.16; Zn, 14.55%. IR (KBr,cmÀ1): 3090(w)
m
(C–H
O
O
arom); 2928(w), 2854(w)
1294(m) (C–O).
m(C–H); 1607(m) m(C@N oxime);
OH2
m
Br
Br
Complex 1
2.3.3. Complex 3
A solution of nickel acetate tetrahydrate (0.10 mmol) in metha-
nol (20 ml) was added dropwise to a solution of H2L3 (0.10 mmol)
Br
Br
Table 2
Selected bond lengths and bond angles for complex 1 [Å, °].
N
N
O
N
N
O
O
Y
O
O
O
O
Bond
Distance
Bond
Distance
n
n
M
Y
Mn–O2i
Mn–O2
Mn–O3
2.123(3)
2.123(3)
2.157(3)
Mn–O3i
Mn–N1
Mn–N1i
2.157(3)
2.306(4)
2.306(4)
M
M
O
O
O
O
O
Bond
Angle
Bond
Angle
O2i–Mn–O2
O2–Mn–O3
O2–Mn–O3i
O3–Mn–O3i
O2i–Mn–N1
93.4(2)
94.5(1)
93.7(1)
168.0(2)
172.9(1)
O2–Mn–N1
O3–Mn–N1
O3i–Mn–N1
O2–Mn–N1i
O3–Mn–N1i
79.9(1)
84.6(1)
88.3(1)
172.9(1)
88.3(1)
Br
Br
Complex 2: n = 1, M = Co, Y = H2O
Complex 3: n = 2, M = Ni, Y= CH3OH
Complex 4: n = 1, M = Zn
Symmetry transformations used to generate equivalent atoms: (i) Àx + 1, y, Àz +
Scheme 2. The general structures of the mono- or trinuclear complexes 1, 2, 3 and
4.
1/2.
Fig. 1. ORTEP drawing of the MnII complex showing the local coordination environment of the crystallographically independent MnII center (thermal ellipsoids at 30%
probability).

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W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
in acetone (20 ml) at room temperature. The mixture was stirred at
room temperature for 2 h, and the solution was filtered. Upon
standing the filtrate at room temperature for several weeks, single
crystals suitable for X-ray crystallographic analysis were obtained.
Fig. 2. View of the 1D chain of the MnII complex along the c-axis (hydrogen atoms, except those forming hydrogen bonds, are omitted for clarity).
Fig. 3. ORTEP drawing of complex 2 showing the local coordination environment of the crystallographically independent CoII center (thermal ellipsoids at 30% probability).

W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
2091
The elemental analyses showed that the metal complexes obtained
were composed of a 3:2 ratio of NiII to ligand. This ratio was later
unequivocally confirmed by X-ray crystallographic analyses. Data
for {[NiL3(OAc)(CH3OH)]2Ni}Á2CH3COCH3Á2CH3OH (3), C48H62Br4-
N4Ni3O18(1478.79): Yield, 37.24%. Anal. Calc. for {[NiL3(OAc)-
(CH3OH)]2Ni}Á2CH3COCH3Á2CH3OH: C, 38.97; H, 4.26; N, 3.79; Ni,
11.95. Found: C, 38.99; H, 4.25; N, 3.76; Co, 11.91%. IR (KBr,
Thornton [17], the metal–oxygen and metal–nitrogen frequency
assignments are at times very difficult.
3.2. Structure analyses
In order to determine the correct configuration of the com-
plexes, X-ray crystallographic studies have been realized for com-
plexes 1, 2, 3 and 4.
cmÀ1): 3412(vw)
(C@N oxime); 1304(m)
m(O–H); 2937(w), 2882(w)
m(C–H); 1605(m)
m
m(C–O).
3.2.1. Crystal structure of 1
Single crystal determination shows that complex 1 forms a self-
assembling continual supramolecular structure by hydrogen-
2.4. X-ray diffraction crystallography
A single crystal suitable for detection was selected and subse-
quently glued to the tip of a glass fiber. The determination of the
crystal structure at 25 °C was carried out with an X-ray diffractom-
eter (Bruker Smart-1000 CCD) using graphite-monochromated Mo
bonding interactions and
p–p stacking. Complex 1 is crystallized
in the monoclinic system, space group C2/c. The coordination
geometry around the MnII ion can be best described as slightly dis-
torted octahedral geometry with a hexa-coordination. In complex
1 (Fig. 1), the two phenolic oxygen atoms and the two oxime nitro-
gen atoms of (L1)2À unit constitute the basal plane, and two oxygen
atoms of the coordinated water molecules are occupying the axial
positions. The bond distances of Mn–N(2.306(4) Å) and Mn–
O(2.123(3) Å) (Table 2) of phenolic oxygen are in the range ob-
served for similar systems [14]. The four N2O2 donor atoms of
(L1)2À unit are approximately coplanar, and the dihedral angle of
O2–Mn–N1° and O2i–Mn1–N1i is 3.38°. The oxygen atoms in the
axial sites of MnII ion forms a considerably large angle of O3–
Mn–O3i (167.99(16)°). It is noticeably that the bond distance
Mn–O3 (2.157(3) Å) is the same with Mn–O3i, which indicates
Ka radiation (k = 0.71073 Å). All non-hydrogen atoms were refined
with anisotropic thermal parameters. Hydrogen atoms were placed
in calculated positions and included in the final cycles of refine-
ment using a riding model. The programs used for structure solu-
tion and refinement were SHELXS-97 and SHELXL-97, respectively. A
summary of the key crystallographic information for complexes
is given in Table 1.
3. Results and discussion
The synthetic route of the ligands is shown in Scheme 1.
Complexes 1, 2, 3 and 4 have been obtained in yields of 35–43%
by reaction of the tetradentate N2O2 Salen-type ligands with differ-
ent metalline acetate M(OAc)2ÁnH2O (M = Mn, Co, Ni, Zn; n = 4, 4, 4,
2) in a refluxing solvent of anhydrous ethanol. The general struc-
tures of these new mono- or trinuclear complexes are shown in
Scheme 2.
the same coordination abilities of the two l-oxo bridges.
The introduction of the coordinated water molecule in complex
1 successfully lead to the 1D chains assembly of [MnL1(H2O)2]
units by hydrogen-bonding interactions (Fig. 2). Four hydrogen
bonds (O3–H3BÁÁÁO2, O3–H3BÁÁÁBr1, O3–H3CÁÁÁO2 and O3–
H3CÁÁÁBr1) are also formed, each oxygen atom of the coordinated
water molecules in complex 1 is bound to both phenolic oxygen
atoms (O2 and O2i) and bromine atoms (Br1 and Br1i) of (L1)2À unit
from the adjacent monomer. The angle of the two neighboring ben-
zene rings is 3.31° and the mean distance between the two neigh-
3.1. IR spectra analyses
The salient feature of the IR spectrum is the free ligands H2L1,
H2L2 and H2L3 exhibit characteristic C@N stretching bands at
1603, 1612 and 1612 cmÀ1, which appeared at 1601, 1607, 1610
and 1605 cmÀ1 in the MnII, ZnII, CoII and NiII complexes, and the
lower shifting of C@N stretching frequencies verified the coordina-
tion of the oxime nitrogen to MII ions. The typical absorptions for
the C–H vibrations in complexes 1, 2, 3 and 4 were detected in
the range 2854–2937 cmÀ1, which is generally not significantly dif-
ferent from that of the ligands. Infrared spectrum of complex 1
shows the expected absorptions due to the stretching, bending
and wagging modes of water molecules at 3418, 1631 and
546 cmÀ1 (3364, 1635 and 542 cmÀ1 in complex 2), respectively,
which indicate the presence of coordinated water molecules.
The O–H stretching frequency band of complex 3 appears at
3412 cmÀ1, indicating the presence of coordinated methanol mol-
ecules. The absorption characteristic for the phenolic hydroxyl
groups in complex 4 is missing, thus confirming the Zn–O bonds
were formed between the ZnII ion and oxygen atoms of phenolic
groups.
boring benzene rings is 3.698 Å, indicating weak
interaction.
p–p
stacking
Table 3
Selected bond lengths and bond angles for complex 2 [Å, °].
Bond
Distance
Bond
Distance
Co1–O4
Co1–O4ii
Co1–O3
Co1–O3ii
Co1–O5ii
Co1–O5
2.094(3)
2.094(3)
2.103(3)
2.103(3)
2.142(4)
2.142(4)
Co2–O4
Co2–O3
Co2–O6
Co2–O7
Co2–N2
Co2–N1
2.037(3)
2.054(3)
2.059(4)
2.099(4)
2.119(5)
2.132(5)
Bond
Angle
Bond
Angle
O(4)ii–Co(1)–O(4)
O(4)ii–Co(1)–O(3)ii
O(4)–Co(1)–O(3)ii
O(4)ii–Co(1)–O(3)
O(4)–Co(1)–O(3)
O(3)ii–Co(1)–O(3)
O(4)ii–Co(1)–O(5)ii
O(4)–Co(1)–O(5)ii
O(3)ii–Co(1)–O(5)ii
O(3)–Co(1)–O(5)ii
O(4)ii–Co(1)–O(5)
O(4)–Co(1)–O(5)
O(3)ii–Co(1)–O(5)
O(3)–Co(1)–O(5)
O(5)ii–Co(1)–O(5)
180.0(1)
78.4(1)
101.6(1)
101.6(1)
78.4(1)
180.0(1)
88.9(1)
91.2(1)
88.9(1)
91.1(1)
91.2(1)
88.9(1)
91.1(1)
88.9(1)
180.0(1)
O(4)–Co(2)–O(3)
O(4)–Co(2)–O(6)
O(3)–Co(2)–O(6)
O(4)–Co(2)–O(7)
O(3)–Co(2)–O(7)
O(6)–Co(2)–O(7)
O(4)–Co(2)–N(2)
O(3)–Co(2)–N(2)
O(6)–Co(2)–N(2)
O(7)–Co(2)–N(2)
O(4)–Co(2)–N(1)
O(3)–Co(2)–N(1)
O(6)–Co(2)–N(1)
O(7)–Co(2)–N(1)
N(2)–Co(2)–N(1)
80.9(1)
92.7(2)
90.2(2)
89.2(1)
93.4(2)
176.2(2)
86.5(2)
167.3(2)
89.4(2)
87.4(2)
166.3(2)
86.5(2)
92.6(2)
86.2(2)
106.2(2)
The far-infrared spectra of complexes 1, 2, 3 and 4 were also ob-
tained in the region 500–100 cmÀ1 in order to identify frequencies
due to the M–O and M–N bonds. The far-infrared spectra of the
complex 1 shows
quencies at 472 and 440 cmÀ1, and complex 2 for
(Co–N) at 415, 480 cmÀ1; complex 3 for
(Ni–O),
(Zn–N) at 420 and
m
(Mn–O) and
m
(Mn–N) vibration absorption fre-
(Co–O) and
(Ni–N) at
m
m
m
m
455, 473 cmÀ1; complex 4 for
m(Zn–O), m
473 cmÀ1, respectively. These assignments are consistent with
the literature frequency values [14–16] and are not present in
the spectrum of the free ligands. As pointed out by Percy and
Symmetry transformations used to generate equivalent atoms: (ii) Àx + 1, Ày + 1,
Àz + 1.

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W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
3.2.2. Crystal structure of 2
gen atom (O8) from the bridging acetate group. The dihedral angle
between the two coordination planes, N1–Co2–O3 and N2–Co2–
O4, is 5.28(2)°, which indicates significant distortion toward tetra-
hedral geometry from the square planar structure. It is noticeably
that the bond distance Co2–O6 (2.060(3) Å) is different from Co2–
O7 (2.100(2) Å) (Table 3) in complex 2, the oxygen atoms in the ax-
ial sites of CoII forms a considerably large angle of O6–Co2–O7
(176.21(2)°), which indicates the different coordination abilities
of the two oxygen atoms.
The complex 2 crystallizes in the P-1 space group with a linear
trinuclear array of three CoII atoms coupled by both doubly
l-
phenoxo oxygens of (L2)2À and simultaneously two acetate anions
in the syn–syn bridging mode. The coordination geometry around
the terminal CoII centers may be regarded as distorted octahedral
geometry with a hexa-coordination (Fig. 3). The equatorial plane
of each of the two equivalent terminal CoII atoms (Co2 and Co2ii)
are formed by the two O-alkyl oxime nitrogen atoms (N1, N2)
and two
l
-phenoxo oxygen atoms (O3, O4) coming from the
However, the coordination geometry of the central Co1 atom
deviates slightly from an ideal octahedron. The central Co1 atom
(L2)2À moiety. The apical positions are occupied by one oxygen
atom (O7) from the coordinated water molecules and another oxy-
has an O2O2 donor set from four
l-phenoxo oxygen atoms (O3,
Fig. 4. (a) View of a 1D single chain motif within CoII complex along the a-axis (hydrogen atoms, except those forming hydrogen bonds, are omitted for clarity). (b) View of
the 1D single chain motif within CoII complex along the c-axis (hydrogen atoms, except those forming hydrogen bonds, are omitted for clarity). (c) View of the 1D single chain
motifs within CoII complex along the b-axis, showing the channels formed from the linking of the 12-membered rings (hydrogen atoms, except those forming hydrogen
bonds, are omitted for clarity).

W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
2093
O4, O3ii and O4ii) of the two (L2)2À moieties. Meanwhile, each of
the two acetate anions bridges the terminal Co2 and central Co1
atoms in a syn–syn fashion. Hence the central Co1 atom finally
has an O2O2O2 donor set (four equatorial oxygen atoms coming
the non-coordinating ethanol molecule are linked by intermolecu-
lar hydrogen bonds to form the other 1D infinite chain along the c-
axis (Fig. 4b).
In addition, there exist intermolecular hydrogen bonds, O8–
H8ÁÁÁO5, which is formed between the oxygen atoms (O5) of the
bridged acetate ions and the –OH group of a non-coordinating eth-
anol molecule (–O8H8); C1–H1BÁÁÁO9, which is formed between
the oxygen atoms (O9) of the non-coordinating ethanol molecule
and the –C1H1B group of the O-alkyl chain of (L2)2À unit. This link-
age is further stabilized by another hydrogen-bond interactions,
from four deprotonated l
-phenoxo oxygens of the two (L2)2À moi-
eties and two axial oxygen atoms from the bridging acetates). It is
interesting that the coordinated angle (O5–Co–O5ii) is 180°, which
is along the octahedral central axis of two
l-acetato ligands with
Co1. The trinuclear structure is probably stabilized by the two
l-
acetato ligands bridging Co1–Co2 and Co1–Co2ii, which neutralize
the whole charge of complex 2. Similar trinuclear structures sup-
ported by two acetato ligands are also found in salicylideneimine
complexes containing ZnII [18], CdII [19], and CuII [11].
C21–H21BÁÁÁpcentroid(C11–C16) and C19–H19AÁÁÁ
pcentroid(C4–C9), from
between each of –CH group of the two non-coordinating ethanol
molecules and each of two aromatic rings of (L2)2À unit, respec-
tively. Consequently, 2 is stabilized by different hydrogen-bond
interactions in an infinite chain along the b-axis (Fig. 4c).
The complex 2 contains five non-coordinating ethanol mole-
cules and there are complicated hydrogen-bonding interactions
in the structure of 2 (Fig. 4). The complex 2 is stabilized by a pair
of C7–H7ÁÁÁO2 hydrogen bonds linking both molecules into an 1D
infinite chain parallel to the a-axis (Fig. 4a). Furthermore, Each
oxygen atom O10 of the two non-coordinating ethanol molecule
is hydrogen-bonded to the –C18H18B group of the bridged acetic
ions, while its –O10H10 group and –C23H23A group is hydro-
gen-bonded to the oxime oxygen atom O1 of the ligands and the
oxygen atom O6 of the bridged acetic ions. Thus, complex 2 and
It is interesting that two coordinating water molecules and four
non-coordinating ethanol molecules are linked through hydrogen
bonds, O9–H9ÁÁÁO8, O7–H7BÁÁÁO8 and O7–H7AÁÁÁO9, to form a
slightly disordered 12-membered hexagon, which shows a nearly
ideal chair conformation cavities. The crystal packing of complex
2 shows that a notable feature of this structure resides in the for-
mation of a new 3D hydrogen-bonding supramolecular networks
through intermolecular C–HÁÁÁO, O–HÁÁÁO and C–HÁÁÁ
p interactions.
It is noteworthy that the channels composing of six O–HÁÁÁO hydro-
gen bonds run along the a-axis (Fig. 4c), having dimensions of
approximately 5.975 Â 4.684 Å as defined by the oxygen–oxygen
distances.
3.2.3. Crystal structure of 3
ꢀ
The complex 3 crystallizes in the triclinic space group P1, which
consists of three nickel atoms, two (L2)2À moieties, two acetate
ions, two coordinated methanol molecules, two crystallizing meth-
anol and two crystallizing acetone molecules (Fig. 5). All the nickel
atoms of 3 have an octahedral geometry. The structural features of
3 are very similar to those of 2 except that the apical positions of
the distorted octahedral coordination geometry around the termi-
nal NiII centers (Ni2) are not occupied by an oxygen atom from the
coordinated water but one oxygen atom (O7) from the coordinated
methanol molecule.
The complex 3 contains uncoordinated methanol molecule and
there are hydrogen-bond interactions between the methanol mol-
ecule and {[NiL3(OAc)(CH3OH)]2Ni} unit as shown in Fig. 6. Se-
lected bond lengths and bond angles data are given in Table 4.
Each of the hydroxyls (–O8H8) in two crystallizing methanol mol-
ecules bonded to the oxygen atom (O5) of the bridging acetate
group, respectively. Simultaneously, each of the hydroxyls
Fig. 5. ORTEP drawing of NiII complex showing the local coordination environment of
the crystallographically independent NiII center (thermal ellipsoids at 30%
probability).
Fig. 6. View of the 1D chain of NiII complex along the a-axis (hydrogen atoms, except those forming hydrogen bonds, are omitted for clarity).

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W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
Table 4
Table 5
Selected bond lengths and bond angles for complex 3 [Å, °].
Selected bond lengths and bond angles for complex 4 [Å, °].
Bond
Distance
Bond
Distance
Bond
Distance
Bond
Distance
Ni1–O3
Ni1–O3iii
Ni1–O4iii
Ni1–O4
Ni1–O5
Ni1–O5iii
2.055(3)
2.055(3)
2.084(4)
2.084(4)
2.108(4)
2.108(4)
Ni2–O6
Ni2–O4
Ni2–O3
Ni2–O7
Ni2–N1
Ni2–N2
2.006(4)
2.029(4)
2.042(4)
2.090(5)
2.094(5)
2.106(5)
Zn1–O11
Zn1–O9
Zn1–O8
Zn1–O3
Zn1–O7
Zn1–O4
Zn2–O10
Zn2–O3
2.05(1)
2.07(1)
2.11(1)
2.12(1)
2.12(1)
2.15(1)
1.96(1)
1.98(1)
Zn2–N2
Zn2–O4
Zn2–N1
Zn3–O7
Zn3–O12
Zn3–N4
Zn3–O8
Zn3–N3
2.07(2)
2.07(1)
2.11(2)
1.98(1)
1.99(1)
2.06(2)
2.07(1)
2.12(2)
Bond
Angle
Bond
Angle
O3–Ni1–O3iii
O3–Ni1–O4iii
O3iii–Ni1–O4iii
O3–Ni1–O4
180.0(2)
103.3(2)
76.7(2)
76.7(2)
103.3(2)
180.00(1)
90.6(2)
89.4(2)
90.5(2)
89.5(2)
89.4(2)
90.6(2)
89.5(2)
90.5(2)
180.00(1)
O6–Ni2–O4
O6–Ni2–O3
O4–Ni2–O3
O6–Ni2–O7
O4–Ni2–O7
O3–Ni2–O7
O6–Ni2–N1
O4–Ni2–N1
O3–Ni2–N1
O7–Ni2–N1
O6–Ni2–N2
O4–Ni2–N2
O3–Ni2–N2
O7–Ni2–N2
N1–Ni2–N2
93.2(2)
93.7(2)
78.2(2)
174.1(2)
92.1(2)
90.0(2)
87.3(2)
164.3(2)
86.1(2)
88.3(2)
88.8(2)
86.2(2)
164.3(2)
88.8(2)
109.5(2)
Bond
Angle
Bond
Angle
O11–Zn1–O9
O11–Zn1–O8
O9–Zn1–O8
O11–Zn1–O3
O9–Zn1–O3
O8–Zn1–O3
O11–Zn1–O7
O9–Zn1–O7
O8–Zn1–O7
O3–Zn1–O7
O11–Zn1–O4
O9–Zn1–O4
O8–Zn1–O4
O3–Zn1–O4
O7–Zn1–O4
O10–Zn2–O3
O10–Zn2–N2
O3–Zn2–N2
175.4(5)
88.0(5)
91.5(5)
91.3(5)
89.4(5)
176.8(5)
89.5(5)
94.9(5)
76.9(5)
99.9(5)
87.4(5)
88.2(5)
104.2(5)
78.9(5)
176.6(5)
102.5(6)
121.9(7)
135.6(6)
O10–Zn2–O4
O3–Zn2–O4
N2–Zn2–O4
O10–Zn2–N1
O3–Zn2–N1
N2–Zn2–N1
O4–Zn2–N1
O7–Zn3–O12
O7–Zn3–N4
O12–Zn3–N4
O7–Zn3–O8
O12–Zn3–O8
N4–Zn3–O8
O7–Zn3–N3
O12–Zn3–N3
N4–Zn3–N3
O8–Zn3–N3
96.2(5)
84.3(5)
88.5(6)
100.2(6)
86.6(6)
87.7(6)
162.6(6)
109.3(5)
139.5(6)
110.4(6)
81.1(5)
95.2(5)
87.6(6)
86.0(6)
104.3(6)
91.8(6)
159.3(5)
O3iii–Ni1–O4
O4iii–Ni1–O4
O3–Ni1–O5
O3iii–Ni1–O5
O4iii–Ni1–O5
O4–Ni1–O5
O3–Ni1–O5iii
O3iii–Ni1–O5iii
O4iii–Ni1–O5iii
O4–Ni1–O5iii
O5–Ni1–O5iii
Symmetry transformations used to generate equivalent atoms: (iii) Àx + 1, Ày + 1,
Àz + 1.
(–O7H7) of two coordinated methanol molecules bonded to the
oxygen atom (O8) of the crystallizing methanol molecules, respec-
tively. The {[NiL3(OAc)(CH3OH)]2Ni} units self-assemble via a pair
of intermolecular C19H19CÁÁÁO1 hydrogen-bonding interactions
where the –CH group of the bridging acetate group acts as the
hydrogen-bond donor to the oxime O atoms forming 1D infinite
chain. A comparison of the structures of the similar complexes
Fig. 7. ORTEP drawing of the ZnII complex showing the local coordination environment of the crystallographically independent ZnII center (thermal ellipsoids at 30%
probability).

W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
2095
reveals an interesting feature: when trinuclear NiII complexes are
formed by both phenoxo- and anion bridges, the resulting
complexes are linear, in which the four l-phenoxo groups occupy
a square plane (four meridional positions) of the central NiII
leaving its axial positions to be occupied by the bridging anions
[18,20].
Fig. 8. (a) View of the 1D single chain motif within ZnII complex along the a-axis (hydrogen atoms, except those forming hydrogen bonds, are omitted for clarity). (b) View of
the 1D single chain motif within ZnII complex along the b-axis (chloroform molecules and hydrogen atoms, except those forming hydrogen bonds, are omitted for clarity). (c)
Extended structure of the ZnII complex, showing the chloroform molecules occupied ‘‘grottos” running along c-axis.

2096
W.-K. Dong et al. / Polyhedron 29 (2010) 2087–2097
3.2.4. Crystal structure of 4
ture was determined. The blue-green emission for the ZnII complex
can be observed, where the maximum emission wavelength at
464 nm. The excitation peak of the complex was located at around
378 nm. It can be also seen that the intensity of the excitation is
stronger than the emission for the complex. The Stokes shift be-
tween the maximum wavelength of fluorescence emission spec-
trum and the fluorescence excitation spectrum was 86 nm. This
red-shift might be related to the coordination of zinc atom with
the ligand, which makes the conjugated system larger.
The asymmetric units of complex 4 contains three ZnII atoms, two
(l
-L2)2À units, two acetate ions and one chloroform molecule (Fig. 7).
The central ZnII (Zn1) is hexa-coordinated, the coordination sphere is
completed by
[Zn(L2)] chelates, and both of oxygen atoms O9 and O11 from the
ligating acetate ions which adopt a familiar O–C–O fashion, and
l-phenoxo oxygen atoms (O3, O4, O7, O8) from two
l
constitute a slightly distorted octahedral geometry. It is noteworthy
that the terminal ZnII ions (Zn2 and Zn3) are both penta-coordinated,
andlocated in theN2O2 moieties of theligand. Theoxygen atoms O10
and O12 from the bridging acetate ions are also coordinated to Zn2
and Zn3, respectively. This is different from2 and 3, and the only pos-
sible explanation for this change might be the templating effect
resulting from the different transitional metal ions due to all the
complexes crystallized under nearly the same conditions. Conse-
quently, the coordination geometry around Zn2 and Zn3 approaches
to a distorted square pyramid. The trinuclear structure is stabilized
4. Conclusions
Four divalent transition metal combinations with three Salen-
type bisoxime ligands have been has resulted in the crystallization
of four supramolecular complexes with 1D chain, 2D and 3D net-
works structural motifs. Complex 1 adopts a slightly distorted
octahedral geometry with a hexa-coordination. And the introduc-
tion of the coordinated water molecule successfully lead to the
assembly of the 1D chains by hydrogen-bonding interactions. Com-
plexes 2 and 3 are rigorously centrosymmetric, the central metal
ion NiII or CoII sits on a crystallographic inversion center in the
crystal. The structure of 2 and 3 adopts a slightly distorted octahe-
dral geometry for every hexa-coordinated MII center. In 4, the
asymmetric unit contains three ZnII ions, the central ZnII is six-
coordinated adopting a slightly distorted octahedral geometry,
the two terminal ZnII ions are five-coordinated, and the coordina-
tion geometry approaches to a distorted square pyramid. Although
1 and 3 display 1D supramolecular chains, the different coordina-
tion environments (mononuclear in 1, trinuclear in 2) provoke
divergence in the structures and aggregations of the chain sub-
units. Complex 2 forms the 3D hydrogen-bonding supramolecular
networks possessing a channel, while 4 exhibits the 2D hydrogen-
bonding supramolecular networks with the formation of ‘‘grottos”
occupied by chloroform molecules through intermolecular hydro-
gen-bond interactions.
by the two l-acetato ligands bridging Zn1–Zn2 and Zn1–Zn3, which
neutralize the whole charge of the complex (Table 5).
Analysis of the crystal packing of 4 shows that a notable feature
of this structure resides in the formation of a new 2D hydrogen-
bonding supramolecular networks through intermolecular C–
HÁÁÁBr, C–HÁÁÁCl, C–HÁÁÁO and C–HÁÁÁ
Fig. 8, complex 4 monomers are linked by the intermolecular
C17–H17AÁÁÁBr1, C9–H9ÁÁÁO12 and C1–H1AÁÁÁ centroid (C27–C32) inter-
p(Ph) interactions. As shown in
p
actions into 1D infinite chains along the a-axis (Fig. 8a). Moreover,
the molecules are further linked by intermolecular C23–H23ÁÁÁBr1
hydrogen-bonds interactions to form the others 1D infinite chain
along b-axis. In addition, the adjacent chains along b-axis are fur-
ther held together by the intermolecular C26–H26ÁÁÁBr1 hydrogen
bonds (Fig. 8b). Obviously, the bromine atoms could be considered
as the 3-connected nodes, and assemble the chains into 2D supra-
molecular network structure parallel to the ab planes.
The most significant feature is the formation of ‘‘grottos” running
throughtheinter-chains region (Fig. 8c). The dimensions of the ‘‘grot-
tos” are approximately 10.6 Â 9.2 Å as defined by the shortest chan-
nel metal–metal distances. It is noteworthy that the uncoordinated
guest chloroform molecules are situated in the ‘‘grottos” through
intermolecular C36–H36BÁÁÁCl2 hydrogen-bond interactions.
5. Supplementary data
Supplementary data CCDC 696151, 696146, 696133 and
696150 contain the supplementary crystallographic data for 1, 2,
3 and 4. These data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html, or from the Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ,
UK; fax: (+44) 1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk.
3.3. Photophysical properties of ligand H2L1, H2L2, H2L3 and of the
complexes
The UV–Vis absorption spectra of the three ligands and their
corresponding complexes in diluted DMF solution. We can see
the absorption peaks of the complexes are obviously different from
those of the ligands upon complexation. The electronic absorption
spectrum of Salen-type ligands H2L1, H2L2 and H2L3 consist of two
Acknowledgments
relatively intense bands centered at 266 and 325 nm (324 nm for
H2L3), assigned to the
p–p transitions of the benzene ring of sali-
*
cylaldehyde and the oxime group, respectively. Upon coordination
of the ligand, the absorption bands at about 325 nm disappears
from the UV–Vis spectra of the transition metal complexes, which
This work was supported by the Foundation of the Education
Department of Gansu Province (No. 0904-11) and the ‘Jing Lan’ Tal-
ent Engineering Funds of Lanzhou Jiaotong University, which are
gratefully acknowledged.
indicates that the oxime nitrogen atom is involved in coordination
*
to the metal ion. The intraligand
p–p transition of the oxime
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