Hydrothermal syntheses, structures and properties of three cyclic tetranuclear complexes and one 1D chain complex with 3,5-dinitrosalicylate

Article abstract of DOI:10.1016/j.poly.2007.04.028

The hydrothermal reactions of Co(OAc)₂ · 4H₂O, 3,5-dinitrosalicylate (3,5-(NO₂)₂sal) and 2,2′-bipyridine (2,2′-bipy) with different reaction periods give metallamacrocycles 1 and 2 with the same chemical formula Co₄(2,2′-bipy)₄{3,5-(NO₂) ₂sal}₄. Replacing Co(OAc)₂ · 4H₂O with Zn(NO₃)₂ · 6H₂O, using the same synthetic procedures, results in the formation of compound [Zn(2,2′-bipy){3,5-(NO₂)₂sal}]_n (3) with a 1D chain structure and the metallamacrocycle compound Zn₄(2,2′-bipy)₄{3,5-(NO₂) ₂sal}₄ (4). Compounds 1 and 2 crystallize as two different polymorphs of cyclic tetranuclear compounds. Compounds 3 and 4 are polymorphic too. The compounds 1 and 4 are isomorphous. The weak coordination interactions have significant influence on the spacial orientations of the 3,5-(NO₂)₂sal ligand, and may affect the crystallization processes. There are antiferromagnetic interactions in the cyclic tetranuclear cobalt(II) compounds 1 and 2. Compound 3 exhibits weak fluorescent emission in the solid state at room temperature.

Full text of DOI:10.1016/j.poly.2007.04.028

Polyhedron 26 (2007) 3849–3856
www.elsevier.com/locate/poly
Hydrothermal syntheses, structures and properties of three
cyclic tetranuclear complexes and one 1D chain complex
with 3,5-dinitrosalicylate
a,
c
De-Cai Wen a,b, Shi-Xiong Liu *, Joan Ribas
a
Department of Chemistry, Fuzhou University, Fuzhou 350002, PR China
Department of Chemistry, Longyan University, Longyan 364000, PR China
`
Departament de Quı´mica Inorganica, Universitat de Barcelona, Diagonal, 647, 08028 Barcelona, Spain
b
c
Received 13 February 2007; accepted 13 April 2007
Available online 5 May 2007
Abstract
The hydrothermal reactions of Co(OAc)2 Æ 4H2O, 3,5-dinitrosalicylate (3,5-(NO2)2sal) and 2,20-bipyridine (2,20-bipy) with different
reaction periods give metallamacrocycles 1 and 2 with the same chemical formula Co4(2,20-bipy)4{3,5-(NO2)2sal}4. Replacing Co-
(OAc)2 Æ 4H2O with Zn(NO3)2 Æ 6H2O, using the same synthetic procedures, results in the formation of compound [Zn(2,20-bipy)-
{3,5-(NO2)2sal}]n (3) with a 1D chain structure and the metallamacrocycle compound Zn4(2,20-bipy)4{3,5-(NO2)2sal}4 (4). Compounds
1 and 2 crystallize as two different polymorphs of cyclic tetranuclear compounds. Compounds 3 and 4 are polymorphic too. The
compounds 1 and 4 are isomorphous. The weak coordination interactions have significant influence on the spacial orientations of the
3,5-(NO2)2sal ligand, and may affect the crystallization processes. There are antiferromagnetic interactions in the cyclic tetranuclear
cobalt(II) compounds 1 and 2. Compound 3 exhibits weak fluorescent emission in the solid state at room temperature.
Ó 2007 Elsevier Ltd. All rights reserved.
Keywords: Metallamacrocycle; Supramolecular isomerism; Hydrothermal synthesis; Cobalt complex; Zinc complex
1. Introduction
been focused on the study of polymorphs and isomorphous
compounds in supramolecular chemistry [3,4].
Self-assembly in metallamacrocycles is a growing area at
the forefront of modern supramolecular chemistry. Many
diverse metallamacrocycles, such as molecular triangles,
squares, rectangles, pentagons and hexagons, have been
synthesized [1,2]. Pd(II) and Pt(II) units and N-donor
ligands are the most favorite building blocks, and these
species are highly charged. Except for 4,40-bipy derivatives
and imidazolate derivatives, most of the ligands used in the
formation of metallamacrocycles are easily broken during
hydrothermal reactions. Therefore, most of the syntheses
of metallamacrocycles are solution reactions. Formation
of metallamacrocycles by hydrothermal reactions is quite
rare. On the other hand, considerable research effort has
Many carboxylate ligands have been shown to be good
building blocks in the preparation of polynuclear com-
plexes with desired topologies owing to their rich coordina-
tion modes [5]. Although a lot of carboxylate complexes
have been studied, reports on the syntheses and magnetic
properties of pentacoordinated cobalt(II) carboxylate com-
plexes are far less in number.
We found that the choice of ligand plays an important
role in preparing new metallamacrocycles. The self-assem-
bly of decanuclear metallacrowns based on 3d-series metals
M(III) with N-acyl salicylhydrazides was reported in our
group [6a]. As shown in Scheme 1, the fully deprotonated
salicylate(sal2ꢀ) can act in two coordination modes: mon-
ochelating-bridging (Ia) and bichelating (Ib). Acting as
mode Ib, sal2ꢀ may be a good linker to generate neutral
metallamacrocycles with M(II), sal2ꢀ in this case is similar
*
Corresponding author. Tel./fax: +86 591 83729860.
E-mail address: shixiongliu@yahoo.com (S.-X. Liu).
0277-5387/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.poly.2007.04.028

3850
D.-C. Wen et al. / Polyhedron 26 (2007) 3849–3856
O
N
R
M1
M1
M1
M1
O
O
N
O
O
O
O3
O2
O
N
O
M2
M2
M2
M2
O1
O
sal2-(Ia)
sal2-(Ib)
shi3-(II)
xshz3-(III)
Scheme 1. Binding models of sal2ꢀ in complexes 1–4 and binding mode of shi3ꢀ and xshz3ꢀ ligands.
48h
1
M = Co
3, 5-(NO2)2sal2-
+
72h
48h
hydrothermal
reaction
2
3
M2+ + 2, 2'-bipy
M = Zn
72h
3
4
+
Scheme 2. Formation pathways of complexes 1–4.
to xshz3ꢀ (N-substituted salicylhydrazidate, H3xshz) or
shi3ꢀ (substituted salicylhydroxamic acid, H3shi) [1a,6,7].
There is a weak coordination between M2 and O2 in model
Ib. The alternation between the existence and the non-exis-
tence of weak coordination may lead to polymorphs.
As a continuation of our effort in the formation of
metallamacrocycles, we attempted to explore the assembly
of metallamacrocycles by hydrothermal reactions, using
3d-series metals M(II), 3,5-dinitrosalicylate (3,5-(NO2)2sal)
and 2,20-bipyridine (2,20-bipy). Herein, we report the syn-
theses, crystal structures and properties of four Co/Zn
3,5-(NO2)2sal complexes. Among the four title compounds,
the cyclic tetranuclear cobalt compounds 1 and 2 are poly-
morphic, and the zinc compounds 3 and 4 are polymorphic
too. Complex 3 has a 1D chain structure while the complex
4 has a cyclic tetranuclear structure. Compounds 1 and 4
form an isomorphous pair. The title complexes 1, 2 and 4
are the first examples of a 3,5-(NO2)2sal complex with a
metallamacrocyclic structure. The formation pathway of
the title compounds 1–4 is shown in Scheme 2. This
research represents an interesting fact that different iso-
meric complexes can be obtained by a simple change of
the reaction time.
mental analyses were conducted on a Perkin-Elmer
2400 CHN elemental analyzer. Magnetic measurements
were carried out in the ‘‘Servei de Magnetoqu´ımica (Uni-
versitat de Barcelona)’’ on polycrystalline samples
(30 mg) with a Quantum Design SQUID MPMS-XL
magnetometer working in the 2–300 K range. The mag-
netic field was 0.1 T. The diamagnetic corrections were
evaluated from Pascal’s constants. Fluorescence spectros-
copy was performed on a Perkin-Elmer LS 55 lumines-
cence spectrometer.
2.2. Synthesis of complexes
2.2.1. Synthesis of Co4(2,20-bipy)4{3,5-(NO2)2sal}4 (1)
A mixture of Co(OAc)2 Æ 4H2O (0.1 mmol), 2,20-bipy
(0.1 mmol), 3,5-dinitrosalicylic acid (0.2 mmol) and dis-
tilled water (10 ml), with the pH value adjusted to 7 by
addition of 1 M NaOH solution, was put into a Teflon-
lined autoclave (20 mL) and then heated at 180 °C for
48 h. Deep brown block-like crystals of 1 in 93% yield
based on Co were obtained. Anal. Calc. for C68H40N16-
O28Co4: C, 46.27; H, 2.2; N, 12.70. Found: C, 46.22; H,
2.25; N, 12.75%.
2. Experimental
2.2.2. Synthesis of Co4(2,20-bipy)4{3,5-(NO2)2sal}4 (2)
The same mixture as that for 1 was used, with the reac-
tion at 180 °C for 72 h, resulting in deep brown block-like
crystal of 2 in 92% yield based on Co. Anal. Calc. for
C68H40N16O28Co4: C, 46.27; H, 2.2; N, 12.70. Found: C,
46.19; H, 2.23; N, 12.76%.
2.1. Materials and general procedures
All of the chemicals were obtained from commercial
sources and were used without further purification. Ele-

D.-C. Wen et al. / Polyhedron 26 (2007) 3849–3856
3851
2.2.3. Synthesis of [Zn(2,20-bipy){3,5-(NO2)2sal}]n (3)
The same synthetic procedure as that for 1 was used
except that Co(OAc)2 Æ 4H2O was replaced by
Zn(NO3)2 Æ 6H2O, giving yellow block-like crystals of 3 in
92% yield based on Zn. Anal. Calc. for C17H10N4O7Zn:
C, 45.61; H, 2.25; N, 12.52. Found: C, 45.55; H, 2.30; N,
12.54%.
atoms are in disordered positions and were refined isotrop-
ically. The crystallographic data for 1–4 are summarized in
Table 1.
3. Results and discussion
3.1. Structural description
2.2.4. Synthesis of Zn4(2,20-bipy)4{3,5-(NO2)2sal}4 (4)
The same mixture as that for 3 was used, with the reac-
tion at 180 °C for 72 h, resulting in 3 in about 70% yield
and light yellow block-like crystals of 4 in about 15% yield
based on Zn. Anal. Calc. for C68H40N16O28Zn4: C, 45.61;
H, 2.25; N, 12.52. Found: C, 45.52; H, 2.26; N, 12.48%.
As illustrated in Fig. 1, the centrosymmetrical molecular
square structure of 1 is built up of four cobalt(II) cations
(Co1, Co2, Co1A and Co2A, symmetry code A, ꢀx + 1,
ꢀy, ꢀz + 1), four bridging 3,5-(NO2)2sal ligands and four
2,20-bipy ligands. Selected bond lengths and angles are
listed in Table 2.
Each CoII ion is pentacoordinated by three oxygen
atoms from two 3,5-(NO2)2sal ligands and two nitrogen
atoms from a 2,20-bipy ligand. The Co1 atom has a dis-
torted square-pyramidal geometry with a s value of 0.03
[8]. However, the coordination sphere of Co2 is between
square-pyramidal and the trigonal bipyramidal, with a s
value of 0.40. When the Co1–O9 and Co2–O2A distances
2.3. X-ray crystallography
X-ray diffraction measurements were carried out at
293 K with graphite monochromated Mo Ka radiation
˚
(k = 0.71073 A) on a Bruker SMART CCD 1000 diffrac-
tometer for 2 and on a Rigaku R-AXIS RAPID Weisseng-
berg IP diffractometer for 1, 3 and 4. The structures were
solved by direct methods (SHELXTL-97) and refined on F2
by full-matrix least-squares techniques. The high values
of the thermal parameters of the oxygen atoms of the
NO2 groups in complexes 1, 2 and 4 suggest disordered
positions of these oxygen atoms. Therefore, these oxygen
˚
˚
(2.504(1) A and 2.705(4) A) are considered as weak coordi-
nation, the Co1 and Co2 centers may be regarded as having
distorted octahedral conformations.
Every one of the four 3,5-(NO2)2sal ligands exhibits a
bichelating coordination mode (Scheme 1(Ib)). Therefore,
neighboring cobalt atoms are connected by one 3,5-
Table 1
Crystallographic data for complexes 1–4
Compound
1
2
3
4
Formula
C
68H40N16O28Co4
C68H40N16O28Co4
1764.88
monoclinic
P21/c
14.715(2)
21.907(3)
21.593(3)
90
94.865(2)
90
6936(1)
4
C17H10N4O7Zn
447.66
monoclinic
P21/c
12.411(5)
16.008(5)
8.721(3)
90
93.84(2)
90
1729.8(1)
4
1.473
293(2)
1.473
C68H40N16O28Zn4
1790.64
monoclinic
P21/c
12.2799(1)
13.5024(3)
22.1376(6)
90
102.282(2)
90
3586.6(1)
2
Formula weight
Crystal system
Space group
1764.88
monoclinic
P21/c
13.015(3)
12.842(3)
21.541(6)
90
103.235(9)
90
3505(2)
2
˚
a (A)
˚
b (A)
˚
c (A)
a (°)
b (°)
c (°)
3
˚
V (A )
Z
Dcalc (g/cmꢀ3
T (K)
)
1.672
293(2)
1.031
1784
1.690
293(2)
1.042
3568
1.658
293(2)
1.420
1808
l (mmꢀ1
F(000)
)
904
h
minimum, hmaximum(°)
3.17, 27.47
ꢀ15 ! 16
ꢀ16 ! 16
ꢀ27 ! 27
0.0359
1.86, 25.00
ꢀ17 ! 17
ꢀ26 ! 25
ꢀ24 ! 25
0.0538
3.03, 27.47
ꢀ16 ! 16
ꢀ20 ! 20
ꢀ10 ! 11
0.0235
1.70, 27.48
0 ! 15
0 ! 17
ꢀ28 ! 28
0.0538
hminimum–maximum
kminimum–maximum
lminimum–maximum
Rint
Number of unique data
Number of observed
Number of variables
R1 [I > 2r(I)]
7979
5784
517
0.0550
11595
6468
1041
0.0439
3954
3448
262
0.0258
8200
4145
515
0.0565
wR2 [I > 2r(I)]
0.1516
0.1054
0.0666
0.1441
Goodness-of-fit
(Dp)maximum,minimum (e/A )
(D/r)maximum, (D/r)minimum
1.063
0.944
1.032
0.949
3
˚
0.792 (ꢀ0.638)
0.690 (ꢀ0.432)
0.316 (ꢀ0.238)
0.674 (ꢀ0.570)
0.001, 0.000
0.001, 0.000
0.000, 0.000
0.001, 0.000

3852
D.-C. Wen et al. / Polyhedron 26 (2007) 3849–3856
95.05(1)°, respectively, indicating a slight deviations from
an ideal square geometry.
Adjacent tetranuclear metallamacrocycles are further
connected to each other by C–H. . .O hydrogen bonds [9]
between the C–H group of the 2,20-bipy ligand and the oxy-
gen atom in the NO2 groups of the 3,5-(NO2)2sal ligand,
resulting in an extended 3D network structure (Fig. S1).
˚
The H. . .O distances are in the range of 2.43–2.53 A.
Detailed data are given in Table S1.
On comparison with the many substituted salicylhydr-
oxamic acid and N-substituted salicylhydrazidate com-
plexes, only a few 3,5-(NO2)2sal complexes have been
found [10]. There are two types of structure for the known
five 3,5-(NO2)2sal complexes, i.e. a 1D structure for
[CoII(phen){3,5-(NO2)2sal2ꢀ}] [10b] and [Mn(phen)-
{3,5-(NO2)2sal2ꢀ}] [10c] and a discrete multinuclear struc-
ture for the other three complexes. To our knowledge, the
title complexes 1, 2 and 4 are the first examples of any
3,5-(NO2)2sal complex with a metallamacrocycle structure.
The molecular structure of complex 2 is shown in Fig. 2.
Selected bond lengths and angles are listed in Table 3. The
cyclic tetranuclear complex molecule Co4(2,20-bipy)4-
{3,5-(NO2)2sal}4 (2) contains four cobalt(II) cations
(Co1, Co2, Co3 and Co4), four 3,5-(NO2)2sal ligands and
four 2,20-bipy ligands. Two of the four 3,5-(NO2)2sal
ligands bridge two neighboring [Co(2,20-bipy)]2+ corners
through one bridging carboxylate oxygen atom (O2 or
O16). For the other two 3,5-(NO2)2sal ligands, each one
bridges two neighboring [Co(2,20-bipy)]2+ corners through
two oxygen atoms (O8 and O9 or O22 and O23) in the car-
boxylate group. Therefore, four cobalt cations and four
3,5-(NO2)2sal ligands construct a molecular rhomboid
structure with a Co4O6C2 core. The molecular rhomboid
structure in 2 is different from the molecular square struc-
ture in 1. The four neighboring Co. . .Co distances in the
Co4O6C2 core are 5.116(1), 4.247(1), 5.209(2) and
Fig. 1. Molecular structure of complex 1 with 30% probability ellipsoids,
hydrogen atoms are omitted for clarity. Symmetry code A, ꢀx + 1, ꢀy,
ꢀz + 1. Only one orientation of the disordered NO2 groups is presented.
Table 2
a
˚
Selected bond lengths (A) and angles (°) for complexes 1 and 4
Complex 1
Complex 4
Co(1)–O(2)
Co(1)–O(3)
Co(1)–O(8)
Co(1)–N(3)
Co(1)–N(4)
Co(2)–O(9)
Co(2)–O(10)
Co(2)–O(1A)
Co(2)–N(7)
Co(2)–N(8)
2.026(3)
1.995(3)
2.078(3)
2.115(3)
2.116(3)
2.027(2)
1.978(3)
2.010(3)
2.108(3)
2.064(3)
Zn(1)–O(2)
Zn(1)–O(3)
Zn(1)–O(8)
Zn(1)–N(4)
Zn(1)–N(3)
Zn(2)–O(9)
Zn(2)–O(10)
Zn(2)–O(1A)
Zn(2)–N(7)
Zn(2)–N(8)
2.041(3)
1.979(3)
2.003(3)
2.154(4)
2.095(4)
2.013(3)
2.016(4)
2.025(4)
2.153(5)
2.072(4)
O(3)–Co(1)–O(2)
O(3)–Co(1)–O(8)
O(2)–Co(1)–O(8)
O(3)–Co(1)–N(3)
O(2)–Co(1)–N(3)
O(8)–Co(1)–N(3)
O(3)–Co(1)–N(4)
O(2)–Co(1)–N(4)
O(8)–Co(1)–N(4)
N(3)–Co(1)–N(4)
O(9)–Co(2)–O(10)
O(9)–Co(2)–O(1A)
O(10)–Co(2)–O(1A)
O(9)–Co(2)–N(7)
O(10)–Co(2)–N(7)
O(1)A–Co(2)–N(7)
O(9)–Co(2)–N(8)
O(10)–Co(2)–N(8)
O(1)A–Co(2)–N(8)
N(7)–Co(2)–N(8)
a
90.6(1)
96.2(1)
91.4(1)
97.5(1)
92.2(1)
165.8(1)
102.0(1)
164.0(1)
97.0(1)
76.5(1)
88.5(1)
151.4(1)
91.7(1)
90.7(1)
175. 4(1)
91.2(1)
115.9(1)
98.5(1)
92.4(1)
77.8(1)
O(3)–Zn(1)–O(2)
O(3)–Zn(1)–O(8)
O(2)–Zn(1)–O(8)
O(3)–Zn(1)–N(3)
O(2)–Zn(1)–N(3)
O(8)–Zn(1)–N(3)
O(3)–Zn(1)–N(4)
O(2)–Zn(1)–N(4)
O(8)–Zn(1)–N(4)
N(3)–Zn(1)–N(4)
O(9)–Zn(2)–O(10)
O(9)–Zn(2)–O(1A)
O(10)–Zn(2)–O(1A)
O(9)–Zn(2)–N(7)
O(10)–Zn(2)–N(7)
O(1)A–Zn(2)–N(7)
O(9)–Zn(2)–N(8)
O(10)–Zn(2)–N(8)
O(1)A–Zn(2)–N(8)
N(7)–Zn(2)–N(8)
90.1(1)
105.9(2)
95.2(1)
112.6(2)
92.2(2)
140.8(2)
97.2(2)
169.0(2)
90.8(2)
77.4(2)
87.8(1)
144.0(2)
90.9(2)
92.9(2)
173.5(2)
92.3(2)
118.8(2)
96.5(2)
97.0(2)
77.6(2)
˚
4.370(1) A. The Co–Co–Co angles in the core are
101.10(1)°, 79.83(1)°, 101.35(1)° and 77.71(1)°.
Symmetry code: A, ꢀx + 1, ꢀy, ꢀz + 1.
(NO2)2sal ligand through the bridging oxygen atoms (O9,
O2A, O9A and O2), generating a Co4O4 core of the molec-
ular square. The four CoII ions in the core are exactly
coplanar. The Co. . .Co distances in the core are 4.319(2)
˚
and 4.617(9) A along the side and 6.594(19) and
Fig. 2. Molecular structure of complex 2 with 30% probability ellipsoids,
hydrogen atoms are omitted for clarity. Only one orientation of the
disordered NO2 groups is presented.
˚
6.038(1) A across the diagonal. The angles Co2–Co1–
Co2A and Co1–Co2–Co1A in the core are 84.95(1)° and

D.-C. Wen et al. / Polyhedron 26 (2007) 3849–3856
3853
Table 4. Each ZnII ion is pentacoordinated by three oxygen
atoms of two 3,5-(NO2)2sal ligands and two nitrogen atoms
of a 2,20-bipy ligand. The coordination sphere is between
square-pyramidal and trigonal bipyramidal, with a s value
of 0.32. Each 3,5-(NO2)2sal ligand adopts a monochelat-
ing-bridging mode (Scheme 1(Ia)) and links two ZnII ions
into a 1D chain structure along the c axis. The chain core
is with a [–Zn–O–C–O–]n repeat. The neighboring Zn1. . .
Zn1A distance (Symmetry code: A x, ꢀy + 1/2, z ꢀ 1/2)
Table 3
Selected bond lengths (A) and angles (°) for 2
˚
Co(1)–O(8)
Co(1)–O(3)
Co(1)–O(2)
Co(1)–N(3)
Co(1)–N(4)
Co(2)–O(10)
Co(2)–O(9)
Co(2)–N(8)
Co(2)–O(15)
Co(2)–N(7)
1.968(3)
1.970(3)
2.036(3)
2.056(3)
2.127(3)
1.975(3)
2.001(3)
2.092(3)
2.098(3)
2.114(3)
Co(3)–O(17)
Co(3)–O(22)
Co(3)–O(16)
Co(3)–N(11)
Co(3)–N(12)
Co(4)–O(24)
Co(4)–O(23)
Co(4)–O(1)
Co(4)–N(16)
Co(4)–N(15)
1.971(3)
1.986(3)
2.024(3)
2.067(3)
2.107(3)
1.974(3)
1.995(3)
2.061(3)
2.087(3)
2.103(3)
˚
is 5.132(1) A, and the Zn–Zn–Zn angle is 116.35(1)°. The
1D chains are further connected by C–H. . .O hydrogen
bonds, resulting in a 3D supramolecular network structure
(Fig. S3). The H. . .O distances are in the range 2.602–
O(8)–Co(1)–O(3)
O(8)–Co(1)–O(2)
O(3)–Co(1)–O(2)
O(8)–Co(1)–N(3)
O(3)–Co(1)–N(3)
O(2)–Co(1)–N(3)
O(8)–Co(1)–N(4)
O(3)–Co(1)–N(4)
O(2)–Co(1)–N(4)
N(3)–Co(1)–N(4)
O(17)–Co(3)–O(22)
O(17)–Co(3)–O(16)
O(22)–Co(3)–O(16)
O(17)–Co(3)–N(11)
O(22)–Co(3)–N(11)
O(16)–Co(3)–N(11)
O(17)–Co(3)–N(12)
O(22)–Co(3)–N(12)
O(16)–Co(3)–N(12)
N(11)–Co(3)–N(12)
119.2(1)
O(10)–Co(2)–O(9)
O(10)–Co(2)–N(8)
O(9)–Co(2)–N(8)
O(10)–Co(2)–O(15)
O(9)–Co(2)–O(15)
N(8)–Co(2)–O(15)
O(10)–Co(2)–N(7)
O(9)–Co(2)–N(7)
N(8)–Co(2)–N(7)
O(15)–Co(2)–N(7)
O(24)–Co(4)–N(15)
O(23)–Co(4)–N(15)
O(1)–Co(4)–N(15)
N(16)–Co(4)–N(15)
O(24)–Co(4)–O(23)
O(24)–Co(4)–O(1)
O(23)–Co(4)–O(1)
O(24)–Co(4)–N(16)
O(23)–Co(4)–N(16)
O(1)–Co(4)–N(16)
88.8(1)
93.9(1)
110.5(1)
102.4(1)
146.5(1)
100.3(1)
167.0(1)
86.3(1)
76.6(1)
88.2(1)
168.3(1)
86.8(1)
89.3(1)
77.4(1)
89.8(1)
100.0 (1)
143.7(1)
94.4(1)
117.4(1)
96.8(1)
91.8(1)
89.4(1)
129.6(1)
110.0(1)
99.5(1)
91.8(1)
89.7(1)
176.3(1)
77.5(1)
123.5(1)
89.6(1)
93.3(1)
111.2(1)
122.4(1)
104.5(1)
87.1(1)
87.9(1)
176.7(1)
77.4(1)
˚
2.670 A (Table S1).
The zinc compound 4 and the cobalt compound 1 are
isomorphous. The centrosymmetrical molecular square
structure in 4 (Fig. S4) is the same as that in 1. Selected
bond lengths and angles of complex 4 are listed in Table
2. In compound 4, each one of four bridging oxygen atoms
(O2, O9, O2A and O9A, symmetry code A, ꢀx + 1, ꢀy,
ꢀz + 1) of the carboxylate groups from four 3,5-(NO2)2sal
ligands bridges two zinc(II) cations to form an Zn4O4 core
in the molecular square structure. The Zn. . .Zn distances in
˚
4 are 4.746(4) and 4.663(2) A along the side and 6.558(4)
˚
and 6.747(1) A across the diagonal. The vertex angles for
Zn2–Zn1–Zn2A and Zn1–Zn2–Zn1A are 91.63(1)° and
88.37(1)°, respectively. It indicates a quite ideal square
geometry.
The coordination geometry for the four zinc(II) cations
in 4 is between square-pyramidal and the trigonal bipyra-
midal, the s values of the Zn1 and Zn2 polyhedra being
0.47 and 0.49, respectively. The Zn1–O9 distance is
2.881(4) A, and the Zn2–O2A distance is 2.744(4) A. When
Zn1–O9 and Zn2–O2A are considered as weakly coordi-
There are two kinds of coordination modes for the four
3,5-(NO2)2sal ligands in complex 2; the two of four ligands
act in the monochelating-bridging mode (Scheme 1a), and
the other two act in the bichelating mode (Scheme 1b), to
give the Co4O6C2 core of the molecular rhomboid.
˚
˚
The coordination geometry of two cobalt atoms, Co1
and Co3, is distorted trigonal bipyramidal, with s values
of 0.78 and 0.90, respectively. However, the coordination
geometry of Co2 and Co4 can be described as a distorted
octahedron because of the weak coordination (Co2–
Table 4
a
˚
Selected bond lengths (A) and angles (°) for 3
Zn(1)–O(1)A
Zn(1)–O(3)
Zn(1)–O(2)
1.983(1)
1.994(1)
2.019(1)
Zn(1)–N(4)
Zn(1)–N(3)
O(2)–Zn(1)–N(4)
2.086(2)
2.107(1)
91.29(5)
˚
˚
O16 = 2.431(3) A, Co4–O2 = 2.518(3) A).
There are some intermolecular C–H. . .O hydrogen
bonds which form an extended 3D structure (Fig. S2).
The H. . .O distances are in the range 2.396–2.523 A
O(1)A1–Zn(1)–O(3)
O(1)A1–Zn(1)–O(2)
O(3)–Zn(1)–O(2)
O(1)A–Zn(1)–N(4)
O(3)–Zn(1)–N(4)
a
93.72(6)
93.92(5)
88.87(5)
122.34(5)
143.82(5)
O(3)–Zn(1)–N(3)
O(2)–Zn(1)–N(3)
N(4)–Zn(1)–N(3)
O(1)A–Zn(1)–N(3)
92.16(5)
163.17(5)
78.03(5)
˚
(Table S1).
102.77(5)
The 1D chain structure of complex 3 is given in Fig. 3.
Selected bond lengths and angles are illustrated in
Symmetry code: A, x, ꢀy + 1/2, z ꢀ 1/2.
Fig. 3. 1D chain of complex 3 with 30% probability ellipsoids. Symmetry code A, x, ꢀy + 1/2, z ꢀ 1/2.

3854
D.-C. Wen et al. / Polyhedron 26 (2007) 3849–3856
nating, the coordination geometries of the ZnII ions can be
described as distorted octahedra. Each 3,5-(NO2)2sal
ligand exhibits a bichelating coordination mode (Scheme
1 Ib).
The C–H. . .O hydrogen bonds in complex 4 (Table S1)
bridge the adjacent tetranuclear metallamacrocycles to cre-
ate an extended 3D network structure (Fig. S5).
molꢀ1 K at 2.00 K. vMT in 2 monotonously decreases to
reach 1.0 cm3 molꢀ1 K at 2.00 K. The shape of these curves
for complexes 1 and 2 is characteristic of the occurrence of
weak antiferromagnetic interactions between the CoII cen-
tres. The antiferromagnetic behaviour in the two complexes
is corroborated by plotting the reduced magnetization (M/
Nb) versus H at 2 K. In both cases the shape of the curve is
typical for an antiferromagnetic coupling, not very strong,
and the values at 5 T are close to 4 Nb instead of 12 (the
theoretical values assuming g = 2.00 for four CoII ions
fully isolated). The pentacoordinated CoII ion does not
present spin–orbit coupling, such as occurs with the octa-
hedral analogues. Thus, they can be treated as systems with
S = 3/2 with the spin-hamiltonian formalism. Taking into
account the tetranuclear character of 1 and 2 we have done
the fit assuming two different J values (alternated) by
means of the CLUMAG program [11]. The best fit is given
3.2. Weak coordination interactions and coordination
orientations
There exist weak coordination interactions M2. . .O2
between the O,O0,O00-tridentate ligand 3,5-(NO2)2sal and
the metal cation (Ib in Scheme 1) in compounds 1, 2 and
4. As shown in Table 5, the absolute value of the torsion
angles O2–C–O1–M2 are between 0.2° and 8.7°, and the
C–O1–M2 bridging angles are in the range 100.2–115.5°.
When there are no weak coordination interactions of
M2. . .O2 (Ia in Scheme 1), the torsion angles O2–C–O1–
M2 in 2 and 3 are between 26.7° and 33.4°, and the C–
O1–M2 bridging angles are in the range 125.6-128.1°.
The strength of the weak coordination interactions among
the four title compounds is of the following order: 1,
4 > 2 > 3. Coincidentally, compounds 1 and 4 have the
molecular square structure, compound 2 has the molecular
rhomboid structure while compound 3 has the chain struc-
ture. This suggests that the weak coordination interactions
have significant influence on the space orientations of the
3,5-(NO2)2sal ligand, and may affect the crystallization pro-
cesses and solid state architectures.
by
the
exchange
parameters
J1 = ꢀ0.41 cmꢀ1
,
,
J2 = ꢀ0.33 cmꢀ1 and g = 2.21 for 1 and J1 = ꢀ0.36 cmꢀ1
J2 = ꢀ0.23 cmꢀ1 and g = 2.30 for 2. The two set of values
are similar, it being interesting to emphasize that for com-
plex 1 the two J values are more similar, which agrees with
8
4
3
6
β
2
4
M/N
3.3. Magnetism
1
0
T
m
χ
2
0
The temperature dependences of vMT (vM being the
magnetic susceptibility for four CoIIions) in complexes 1
and 2 are shown in Figs. 4 and 5 (from 300 K to 2 K),
respectively. vMT at 300 K in 1 and 2 is close to 9 and
10.5 cm3 molꢀ1 K, respectively, and these values are as
expected for four isolated pentacoordinated CoII ions.
vMT in 1 monotonously decreases to reach 0.2 cm3
0
10000 20000 30000 40000 50000
H / Gauss
0
50 100 150 200 250 300
T / K
Fig. 4. Plot of vMT vs. T for complex 1. The solid line represents the best
fit. Inset: plot of the reduced magnetization (M/Nb) at 2 K.
Table 5
A comparison between weak coordination, torsion angles and bridging angles in complexes 1–4
Complex
M2a
M2. . .O2 distance
Weak
coordination
O2–C–O1–M2 torsion angle C–O1–M2 bridging angle Structure type
˚
(A)
(°)
(°)
1
2
Co1
Co2
2.50(1)
2.705(4)
yes
yes
–0.2(4)
8.7(4)
103.2(2)
110.0(2)
molecular square
Co1
3.170(3)
no
26.7(5)
125.6(3)
molecular
rhomboid
Co2
Co3
Co4
2.431(3)
3.251(3)
2.518(3)
yes
no
yes
4.8(4)
ꢀ31.7(5)
ꢀ2.5(4)
100.2(2)
127.8(3)
103.2(3)
3
4
Zn1
3.280(2)
no
ꢀ33.4(2)
8.7(6)
ꢀ1.6(6)
128.1(1)
1D chain
Zn1
Zn2
2.881(4)
2.744(4)
yes
yes
115.5(3)
111.0(3)
molecular square
a
The symbols M2, O2, C, and O1 are the same as those in Scheme 1(Ib).

D.-C. Wen et al. / Polyhedron 26 (2007) 3849–3856
3855
lic tetranuclear pentacoordinated cobalt(II) complexes 1
and 2.
10
8
4
3
2
1
0
Acknowledgements
This project was financially supported by the Natural
Science Foundation of China (Nos. 20431010 and
20171012), the Natural Science Foundation of Fujian
Province, China (E0110010), and the Spanish Government
(Grant BQU2003/00539).
6
β
N
M/
4
T
m
χ
2
0
10000 20000 30000 40000 50000
0
H / G
Appendix A. Supplementary material
0
50 100 150 200 250 300
T / K
CCDC 617368, 617369, 617370 and 617371 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. Supplementary data associ-
ated with this article can be found, in the online version, at
doi:10.1016/j.poly.2007.04.028.
Fig. 5. Plot of vMT vs. T for complex 2. The solid line represents the best
fit. Inset: plot of the reduced magnetization (M/Nb) at 2 K.
a structure that it is more square-like in 1 and more rhom-
boid-like in 2. The small J values are due, in both cases, to
the magnetic pathway created by the carboxylate bridging
groups in a syn–anti configuration. The small overlap
between the magnetic orbitals accounts for the weak cou-
pling observed. This qualitative approach was already
introduced by Kahn when studying this kind of syn–anti
coordination mode [12].
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