Manipulation of molecular and supramolecular structure in cobalt(II) complexes with tetrachloroterephthalate through the influence of different solvents

Article abstract of DOI:10.1002/zaac.200900577

The reactions of cobalt acetates with tetrachloroterephthalic acid (H ₂BDC-Cl₄) in different solvents gave two polymeric and one mononuclear Co^II complexes. X-ray single-crystal structural determination revealed that the ligand BDC-Cl₄ displays a reliable bridging tecton to construct diverse supramolecular architectures through, coordinative bonds or secondary hydrogen-bonding interactions. The complexes [Co(BDC-Cl₄)(DMF)₂(EtOH)₂]_n (1) and {[Co(BDC-Cl₄)(DMF)₂(MeOH)₂]·2DMF} _n (2) demonstrate a one-dimensional (ID) coordination, motif with infinite Co^II-tetrachloroterephthalate chains, which are tuned by different binding solvent systems of DMF/ethanol (EtOH) and DMF/methanol (MeOH). [CO(DMF)₂(H₂O)₄KBDC-Cl₄) (3) represents a two-dimensional (2D) metallosupramolecular network by hydrogen-bonded bridging between the aqua ligand of the mononuclear complex with the uncoordinated BDC-Cl₄ solvates. The spectroscopic, thermal, and fluorescent properties of 1-3 were also investigated.

Full text of DOI:10.1002/zaac.200900577

ARTICLE
DOI: 10.1002/zaac.200900577
Manipulation of Molecular and Supramolecular Structure in Cobalt(II)
Complexes with Tetrachloroterephthalate through the Influence of Different
Solvents
Zhi-Hui Zhang,[a] Sheng-Chun Chen,[a] Huan Xu,[a] Ming-Yang He,[a] and Qun Chen*[a]
Keywords: Tetrachloroterephthalates; Solvent effects; Polymers; Supramolecular chemistry; Cobalt
Abstract. The reactions of cobalt acetates with tetrachloroterephthalic coordination motif with infinite CoII-tetrachloroterephthalate chains,
acid (H2BDC-Cl4) in different solvents gave two polymeric and one which are tuned by different binding solvent systems of DMF/ethanol
mononuclear CoII complexes. X-ray single-crystal structural determi- (EtOH) and DMF/methanol (MeOH). [Co(DMF)2(H2O)4]·(BDC-Cl4)
nation revealed that the ligand BDC-Cl4 displays a reliable bridging (3) represents a two-dimensional (2D) metallosupramolecular network
tecton to construct diverse supramolecular architectures through coor- by hydrogen-bonded bridging between the aqua ligand of the mononu-
dinative bonds or secondary hydrogen-bonding interactions. The com- clear complex with the uncoordinated BDC-Cl4 solvates. The spectro-
plexes [Co(BDC-Cl4)(DMF)2(EtOH)2]n (1) and {[Co(BDC-Cl4)- scopic, thermal, and fluorescent properties of 1–3 were also investi-
(DMF)2(MeOH)2]·2DMF}n (2) demonstrate a one-dimensional (1D) gated.
and CoII [17b] ions. Noticeable changes in the structures can
Introduction
arise from subtle differences in experimental conditions. The
The development of synthetic chemistry brought a great vari-
cobalt ion has a hexacoordinate octahedral arrangement and
the combination of CoII and tetrachloroterephthalate involving
pyridine solvents is well explained in a recent report [17b].
Since a slightly change of the solvent media can significantly
tune the hydrogen-bonding arrays as well as coordination envi-
ronments, different architectures could be obtained by carrying
out the reaction in different solvents. As an ongoing explora-
tion of solvent effects, we consider tetrachloroterephthalate to
form complexes with the classical octahedral cobalt(II) ion by
employing the DMF entities as main solvent medium, because
DMF has been proved to be a versatile guest ligand with varia-
ble binding modes and which is undoubtedly a good partici-
pant of hydrogen bonds.
In this context, we describe herein the solvent-regulating
preparation, structural characterization, and thermal stabilities
of three CoII complexes with the ligand H2BDC-Cl4,
[Co(BDC-Cl4)(DMF)2(EtOH)2]n (1), {[Co(BDC-Cl4)(DMF)2-
(MeOH)2]·2DMF}n (2), and [Co(DMF)2(H2O)4]·(BDC-Cl4)
(3). The luminescent properties of these complexes were also
investigated.
ety of new predesigned polyfunctional ligands in coordination
chemistry and materials science with potential applications in
optics, magnetism, adsorption, ion exchange and catalysis [1–
6]. Equipped with robust and versatile coordination capability,
aromatic dicarboxylate and polycarboxylate compounds at-
tracted considerable attention in the preparation of coordina-
tion polymers and metallosupramolecular constructions with
diverse topologies and permanent porosities [7–10]. Among
them, benzene-1,4-dicarboxylic acid (H2BDC) represents a
popular module to build various open frameworks for solvents
inclusion and/or gas sorption [11–15]. However, correlated li-
gands with unfavorable substituents on the phenyl group were
investigated by only few documents, for instance the studies
on H2BDC analogues with bulky methyl or halogen groups
[11, 14, 16] as well as polymeric supramolecular assemblies
regulated by the solvent [16b]. The corresponding research is
directed in the aspect of crystal engineering to enhance thermal
and chemical stability of the resultant polymeric networks.
Recently, investigations on the solvent effects involved halo-
gen substituted BDC molecules, such as tetrachloroterephthalic
acid (H2BDC-Cl4) [16b, 17] and tetrabromoterephthalic acid
(H2BDC–Br4) [18]. H2BDC-Cl4 was firstly investigated con-
cerning its coordination chemistry and structural diversifica-
tion about transition metal ions, such as MnII [16b], CuII [17a]
Experimental Section
Materials and General Methods
All reagents and solvents for synthesis and analysis were commercially
available and used without further purification, with the exception of
the ligand H2BDC-Cl4, which was prepared according to the literature
procedure [19]. Infrared spectra were recorded with a Nicolet ESP 460
FT-IR spectrometer on KBr pellets in the range of 4000–600 cm–1.
Carbon, hydrogen and nitrogen analyses were performed with a PE-
* Prof. Q. Chen
Fax: +86-519-86330251
E-Mail: chenqunjpu@yahoo.com
[a] Key Laboratory of Fine Petrochemical Technology
Jiangsu Polytechnic University
Changzhou 213164, P. R. China
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Z.-H. Zhang, S.-C. Chen, H. Xu, M.-Y. He, Q. Chen
ARTICLE
2400II (Perkin–Elmer) elemental analyzer. Thermogravimetric (TGA)
experiments were carried out on a SDT-Q600 (ThermoElectron) DSC-
TGA analyzer from room temperature to 800 °C under nitrogen at a
heating rate of 10 °C·min–1. Luminescent spectra of 1–3 in the solid
state were recorded with a Varian Cary Eclipse spectrometer.
X-ray Crystallography
X-ray single crystal diffraction data collections for 1–3 were performed
with a Bruker Apex II CCD diffractometer at room temperature with
Mo-Kα radiation (λ = 0.71073 Å). A semiempirical absorption correc-
tion was applied (SADABS), and the program SAINT was used for
integration of the diffraction profiles [20]. All structures were solved
by direct methods using SHELXS and refined anisotropically for all
non-hydrogen atoms by full-matrix least-squares on F2 with SHELXL
[21]. In general, hydrogen atoms were located geometrically and al-
lowed to ride during the subsequent refinement. Starting positions of
the solvent hydrogen atoms were located in difference Fourier synthe-
ses, and then fixed geometrically with isotropic temperature factors.
Further crystallographic data and structural refinement parameters are
listed in Table 1. Selected bond lengths and angles are given in Ta-
ble 2.
Syntheses of the CoII Complexes
[Co(BDC-Cl4)(DMF)2(EtOH)2]n (1):
A mixture of H2BDC-Cl4
(30.4 mg, 0.10 mmol) and Co(OAc)2·4H2O (24.9 mg, 0.10 mmol) was
dissolved in DMF/EtOH (10 mL, 1:1) whilst stirring for ca. 30 min.
Afterwards, the resultant pink solution was filtered. Upon evaporation
of the filtrate under ambient conditions, pink prismatic crystals were
observed after one week in a yield of 72 % (43.1 mg, on the basis of
CoII acetate). Elemental analysis for C18H26Cl4CoN2O8: calcd. C
36.08; H 4.37; N 4.68 %; found: C 36.21; H 4.23; N 4.60 %. IR: ν =
˜
Table 2. Selected bond lengths /Å and angles /° for complexes 13.
3527 s, 3131 b, 1650 vs, 1603 s, 1495 w, 1413 s, 1384 s, 1334 vs,
1113 m, 1064 w, 836 m, 798 m, 678 s, 620 s cm–1.
Bonds
Angles
1
{[Co(BDC-Cl4)(DMF)2(MeOH)2]·2DMF}n (2): The procedure was
similar to that for 1 except that DMF/EtOH was replaced by DMF/
MeOH (10 mL, 1:1). Pink block-shaped single crystals of 2 resulted
after ten days in a 65 % yield (46.6 mg, on the basis of CoII acetate).
Elemental analysis for C22H36Cl4CoN4O10: calcd. C 36.84; H 5.06; N
Co1–O2
Co1–O3
Co1–O4
2
2.0824(11)
2.1002(13)
2.1242(12)
O2–Co1–O3
O2–Co1–O4
O3–Co1–O4
88.16(5)
87.75(5)
91.87(5)
Co1–O1
Co1–O4
Co1–O3
3
Co1–O3
Co1–O4
Co1–O5
2.0773(11)
2.0793(13)
2.1267(12)
O1–Co1–O4
O1–Co1–O3
O4–Co1–O3
91.29(5)
91.65(5)
90.69(5)
7.81 %; found: C 36.78; H 5.02; N 7.92 %. IR: ν = 3526 s, 3125 b,
˜
1650 vs, 1494 w, 1414 s, 1384 m, 1335 vs, 1251 w, 1114 m, 1063 w,
843 m, 798 m, 678 s, 619 s cm–1.
2.0257(12)
2.1291(12)
2.1480(12)
O3–Co1–O4
O3–Co1–O5
O4–Co1–O5
90.82(5)
88.45(5)
86.79(5)
[Co(DMF)2(H2O)4]·(BDC-Cl4) (3): The procedure was similar to that
for 1 except that DMF/EtOH was replaced by DMF/H2O (10 mL, 1:1),
which afforded pink block crystals of 3 in a 48 % yield (27.8 mg, on
the basis of CoII acetate). Elemental analysis for C14H22Cl4CoN2O10:
calcd. C 29.04; H 3.83; N 4.84 %; found: C 29.12; H 3.83; N 4.82 %. Crystallographic data (excluding structure factors) for the crystal struc-
IR: ν = 3527 s, 3130 b, 1650 vs, 1604 s, 1495 w, 1413 s, 1384 m, tures reported in this paper have been deposited with the Cambridge
˜
1334 vs, 1251 w, 1113 m, 1064 w, 836 m, 798 m, 678 s, 620 s cm–1.
Crystallographic Data Center. Copies of the data can be obtained on
Table 1. Crystallographic data and structure refinement for complexes 1–3.
1
2
3
Formula
C18H26Cl4CoN2O8
599.14
C22H36Cl4CoN4O10
717.28
C14H22Cl4CoN2O10
579.07
Mr
Cryst system
Triclinic
Triclinic
Triclinic
¯
¯
¯
Space group
P1
P1
P1
Crystal size /mm
0.22 × 0.20 × 0.16
9.0573(11)
9.1021(11)
9.9793(12)
64.2770(10)
82.4490(10)
61.3530(10)
647.38(14)
1
0.24 × 0.22 × 0.18
8.4499(14)
9.1077(15)
11.4214(19)
90.705(2)
105.211(3)
107.235(2)
806.2(2)
0.25 × 0.22 × 0.17
5.7811(15)
8.587(2)
a /Å
b /Å
c /Å
12.087(3)
95.720(3)
102.039(3)
98.720(3)
574.7(3)
α /°
β /°
γ /°
V /Å3
Z
1
1
Dcalc /g·cm–3
1.537
1.477
1.673
μ /mm–1
1.119
0.918
1.263
F(000)
307
371
295
Reflections, collected/unique
Parameters
5074/2516
154
5825/2822
192
4995/2605
144
Rint
0.0208
0.0191
0.0279
Final R indices [I > 2σ(I)]
Goodness-of-fit on F2
Max. res. peak and hole /e·Å–3
R1 = 0.0268, wR2 = 0.0801
1.101
R1 = 0.0250, wR2 = 0.0767
1.049
R1 = 0.0273, wR2 = 0.0794
1.083
0.340 and –0.348
0.268 and –0.284
0.324 and –0.437
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 1629–1634

Cobalt(II) Complexes with Tetrachloroterephthalate
quoting the depository numbers CCDC-752035, -752036, and -752037
(1–3) (www.ccdc.cam.ac.uk/conts/retrieving.html or from the CCDC,
12 Union Road, Cambridge CB2 1EZ, UK; Fax: +44-1223-3360-33;
E-Mail: deposit@ccdc.cam.ac.uk).
Results and Discussion
Synthesis and General Characterizations
DMF was proven to be a reliable binding guest molecule
when coordinating to MnII and CuII ions [16b, 17]. Its coordi-
nation ability is better than that of MeOH, EtOH, and also the
aqua ligand in mixed solvent media. In this work, we initiate
the combination of cobalt(II) and tetrachloroterephthalate in
three different solvent mixtures, namely DMF/EtOH, DMF/
MeOH, and DMF/H2O (with each of the two components in
equivalent amount). Three resultant CoII complexes could be
isolated through the same procedure by alternating the starting
metal salts with Co(OAc)2, Co(ClO4)2, Co(NO3)2, and CoCl2
(confirmed by IR spectra and elemental analyses), which indi-
cates that in these systems the final products are independent
of the counteranions. In the IR spectra, the broad bands cen-
tered at ca. 3130 cm–1 indicate the O–H stretching of solvents.
The absence of characteristic absorption bands (at ca.
1720 cm–1) ofthe carboxyl moiety in 1–3 suggests complete
deprotonation. The difference between the νas(COO–) and
ν
sym(COO–) indicates the monodentate coordination mode of
each carboxylate group in 1 and 2.
Descriptions of Crystal Structures for Complexes 1–3
[Co(BDC-Cl4)(DMF)2(EtOH)2]n (1) and {[Co(BDC-
Cl4)(DMF)2(MeOH)2]·2DMF}n (2)
Figure 1. (a) Polymeric chain motif of 1 with the asymmetric unit and
CoII coordination environment labeled. Symmetry code: i, –x, –y+1, –
X-ray diffraction analysis revealed that both complexes 1
and 2 crystallize in the triclinic space group P1 with analogous z+1. (b) Polymeric chain motif of 2 with the asymmetric unit and CoII
¯
coordination environment labeled. Symmetry code: i, –x+1, –y+2, –
1D polymeric coordination chain motifs (Figure 1 and Fig-
ure 2). The basic coordination frameworks of them are similar,
z+2. (c) Perspective view of the host/guest system in 2 with DMF
guest molecules highlighted in dark grey.
except that the coordinated guest molecules are DMF/ethanol
in complex 1 and DMF/methanol in complex 2. Different sizes
and shapes of binding alcohol molecules lead to the fact that
there are no free guests in 1 but lattice DMF molecules in 2.
the bis-monodentate BDC-Cl4 spacer into a linear chain run-
¯
In the asymmetric unit of 1, each CoII atom is located at an ning along the [111] direction with adjacent Co···Co separation
inversion center [at (0,1/2,1/2)] and coordinated by six oxygen of 11.416(1) Å. Intramolecular hydrogen-bonding interaction
atoms coming from a pair of carboxylate groups of two centro- was formed between the uncoordinated carboxylate atom O1
symmetric BDC-Cl4 ligands, two DMF, and two ethanol guest and the ligated EtOH molecule (O4–H4···O1i, H4···O1i, and
molecules (Figure 1a). The coordination sphere around CoII O4···O1i distances of 1.81 and 2.626(2) Å, respectively; angle
could be appropriately illustrated as a nearly ideal octahedron, of 161°; symmetry code: i = –x, –y+1, –z+1, see Table 3).
with Co–O bond lengths in the range 2.0824(11) to Additionally, no further hydrogen-bonding interactions were
2.1242(12) Å. In each centrosymmetric BDC-Cl4 molecule, found in the crystal packing of 1.
the rotation angle (φrot) between the tetrachlorinated phenyl
As for compound 2, the asymmetric unit contains one CoII
ring and the carboxylate group is 86.0(2)°; it adopts a nearly ion lying on an inversion center [at (1/2,1,1)], one centrosym-
perpendicular fashion due to the steric effect, which is similar metric BDC-Cl4 ligand, one coordinated DMF molecule and
to the one of other carboxylate compounds with polychlorin- one coordinated methanol molecule, as well as one DMF guest
ated backbone [16b, 22]. As expected, the bond length of car- molecule. A similar hexacoordinate arrangement of the CoII
boxylate C1–O2 [1.256(2) Å] is slightly longer than that of atom also revealed nearly ideal octahedral coordination. Within
C1–O1 [1.233(2) Å] because of its monodentate coordination the BDC-Cl4 ligand, the carboxylate groups deviate from the
mode. As illustrated in Figure 1a, the CoII ions are linked by Cl4-substituted phenyl ring with a dihedral angle of 82.7(5)°,
Z. Anorg. Allg. Chem. 2010, 1629–1634
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Z.-H. Zhang, S.-C. Chen, H. Xu, M.-Y. He, Q. Chen
ARTICLE
[Co(DMF)2(H2O)4]·(BDC-Cl4) (3)
The molecular structure of 3, which is shown in Figure 2a,
is made up of a discrete [Co(DMF)2(H2O)4]2+ cationic unit and
a BDC-Cl4 anion. Two DMF and four aqua molecules surround
the CoII ion to form a nearly ideal octahedron with the metal
ion lying on an inversion center at (1/2,1/2,1) and the Co–O
bond lengths are in the range 2.0257(12)–2.1480(12) Å. In this
case, the uncomplexed tetrachloroterephthalate with the inver-
sion center at (1,1/2,1/2) is fully deprotonated for charge bal-
ance. Additionally, it acts as a secondary acceptor to the cati-
onic complex unit with participation in multiple O–H···O
interactions, which lead to an extended 2D supramolecular ar-
ray. As indicated in Figure 2b, each [Co(DMF)2(H2O)4]2+ moi-
ety generates a pair of Owater–H···Ocarboxylate contacting with
two neighboring tetrachloroterephthalate anions to afford a 1D
hydrogen-bond tape, including a R22(8) hydrogen-bonding pat-
tern [O4–H4A···O1 and O3–H3A···O2i, (symmetry code: i =
–x + 1, –y + 1, –z + 2)] [24]. As a result, adjacent Co···Co
separation within each 1D supramolecular array is
14.421(2) Å, which is significantly longer that the values in
complexes 1 and 2. Another two hydrogen-bonded interactions
(O3–H3B···O1ii and O4–H4B···O5ii, symmetry code: ii = –x +
2, –y + 1, –z + 2), forming a hydrogen-bonding model of R33(8)
graphic set by the combination of O4–H4A···O1 bond [24],
join the neighboring 1D motif into a (4,4) topologic supramo-
lecular net if the cationic units are considered as nodes and the
anionic units are considered as linkers. No significant evident
shows there are other weak interactions, such as hydrogen-
bonding and aromatic interactions, between adjacent layers.
Figure 2. (a) Molecular structure of 3 with the asymmetric unit and
CoII coordination environment labeled. Symmetry code: i, –x + 1, –y
+ 1, –z + 2. (b) Hydrogen-bonding layer of 3 along the ac plane.
Table 3. Possible hydrogen-bonding arrangements in the crystal struc-
tures of 1–3.
D–H···A
D···A /Å H···A /Å D–H···A /° Symmetry code
Structural Comparison of the Supramolecular Networks on
the Basis of Different Coordinated Guests
O4–H4···O1
2.626(2) 1.81
161
167
153
157
173
170
167
140
–x, –y+1, –z+1
O3–H3A···O2 2.615(2) 1.81
In virtue of solvent-tuning strategy, three CoII complexes
with different binding guest molecules were synthesized and
crystallographically characterized. Complexes 1 and 2 adopt a
1D linear coordination motif, whereas complex 3 is a mononu-
clear complex and represents furthermore, a metallosupramo-
lecular assembly with 2D hydrogen-bonding network through
the recognition between anionic acids and discrete CoII solv-
ates is formed. As for previously reported manganese(II) coor-
C5–H5···O5
3.404(2) 2.55
C6–H6A···O5 3.427(3) 2.52
O3–H3A···O2 2.602(2) 1.79
O3–H3B···O1 2.710(2) 1.90
O4–H4A···O1 2.675(2) 1.87
O4–H4B···O5 3.007(2) 2.33
–x+1, –y+1, –z+2
–x+2, –y+1, –z+2
–x+2, –y+1, –z+2
because of the steric effect that affords monodentate coordina- dination polymers, the ligand H2BDC-Cl4 ligand exhibits dif-
tion modes. The final 1D coordination motif joined by bis- ferent binding modes and allows further engineering of the
monodentate BDC-Cl4 spacers runs along the crystallographic dimensionality of the coordination networks with variable aux-
[001] direction with the adjoining Co···Co distance of iliary solvent co-ligands. In the cases of copper(II) coordina-
11.422(2) Å (Figure 1b). Intramolecular O3–H3A···O2 (Ta- tion polymers, the arrangement of the CuII atom with varying
ble 3) interaction was found between the uncoordinated car- coordination mode (from four to six) because of Jahn–Teller
boxylate atom and the ligated MeOH molecule to stabilize the effect, is responsible for the structural diversification besides
resultant coordination structure, as the O4–H4···O1 bond in the the influence of binding-guests. In this work, the CoII coordi-
complex 1. These coordination chains align parallel along a nation modes always represent a typical octahedron. The sol-
axis, leaving 251.1 Å3 interchain space (31.1 % of the unit cell vent systems vary from DMF/EtOH (in 1), DMF/MeOH (in 2)
volume) to accommodate DMF guest molecules (Figure 1c) to DMF/H2O (in 3), and each participating solvent can work
[23] Notably, the DMF guest moieties are anchored to the co- as a binding guest molecule. The BDC-Cl4 anion forms two
ordination chain through hydrogen-bonding to the coordinated coordination polymers, 1 and 2, respectively, with nearly simi-
DMF molecules through C5–H5···O5 and C6–H6A···O5 bonds lar recognition patterns by only varying the alcohol solvent
(Table 3).
factor. Different sizes of the alcohol molecules cause no free
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Cobalt(II) Complexes with Tetrachloroterephthalate
guests in 1 but the inclusion of DMF molecules in 2. Unlikely, range 90 to 220 °C with a peak at 123 °C, which was followed
the assemblies of 1 and 2 are totally dissimilar compared with by a series of weight losses of uncoordinated BDC-Cl4 moie-
a previous reported CoII polymer Co(BDC)(DMF) (BDC = ter- ties and coordinated water ligands that did not end until heat-
ephthalate) [25], which was also obtained from a mixed DMF/ ing to 800 °C.
EtOH solvent system. The complex mentioned above has a
doubly bridging oxygen bound DMF ligand and a bis-bidentate
BDC ligand, thus the final 3D net of the structure has sra
Luminescent Properties
topology. In the case of complex 3, the BDC-Cl4 anion does
not coordinate to CoII ions but gives a metallosupramolecular
aggregate. The reaction of the unsubstituted BDC ligand and
CoII ions in DMF/H2O yielded a similar 1D polymeric chain
like those found in compounds 1 and 2 [26].
Hybrid inorganic–organic frameworks have received atten-
tion as materials capable of excellent photoluminescent proper-
ties since the complexation of organic ligands and metal ions
may induce the enhancement, shift, and quench of the photolu-
minescence compared to those exhibited by the free organic
ligands. In this work, the luminescent properties of complexes
1–3 in the solid state were investigated at room temperature.
The emission spectra of complexes 1 and 2, as well as the
sodium salt of H2BDC-Cl4, under excitation of ca. 340 nm are
shown in Figure 4. For complex 3, the initial luminescence of
Na2BDC-Cl4 was quenched after metal complexation as result
of multiple water ligands and vigorous hydrogen-bonding in-
teraction between water and aromatic molecules. One strong
and one weak emission peak at 478 and 517 nm, respectively,
were observed in the emission spectrum of Na2BDC-Cl4 in
the solid state. Significantly, complexes 1 and 2 have similar
emission maxima of 489 and 500 nm, respectively. The emis-
sion spectra show little red-shift and shape-dissimilar com-
pared with that of free BDC-Cl4 ligand, but they are in agree-
ment with those of the previously reported CuII-BDC-Cl4
polymers [17a].
Thermal Stability
To investigate thermal stabilities of complexes 1–3, Thermo-
gravimetric measurements were carried out from room temper-
ature to 800 °C. The corresponding curves are depicted in Fig-
ure 3. The TG curve of 1 shows that the first two weight losses
from 80 to 200 °C were assigned to be the removal of coordi-
nated DMF molecules (calcd. 24.4 %; found 25.6 %) at 86 and
101 °C. The following weight loss in the temperature range of
144 to 360 °C indicates the decomposition of vague compo-
nents with a peak at 338 °C. Afterwards, slow pyrolysis of the
residual fragment continued from 360 °C and did not end even
when heated to 800 °C. For the TG plot of 2, the weight loss
of 20.7 %, which occurred from 60 to 200 °C with a peak at
82 °C, clearly corresponds to the release of DMF solvents
(calcd. 20.4 %). Afterwards, a sharp weight loss was observed
in the temperature range of 250–375 °C with a peak at 344 °C,
which indicates collapse of the remaining framework. Similar
sluggish weight loss as that of 1 took place from 360 °C and
did not end at 800 °C.
Figure 4. Solid-state emission and excitation (inset) spectra of 1 and
2 at room temperature.
Figure 3. TG curves of 1–3.
Conclusions
We designed and characterized three novel cobalt coordina-
Surprisingly, in the case of complex 3, the release of coordi-
nated DMF subunits happened earlier than the loss of uncoor-
dinated BDC-Cl4 molecules, probably because of the robust tion compounds based on the deliberate choice of BDC-Cl4
hydrogen bonds between coordinated water molecules and ligand and diverse solvents. All complexes have an octahedral
BDC-Cl4 moieties. The corresponding weight loss of DMF arrangement at the CoII atom. The BDC-Cl4 molecule serves
(calcd. 25.2 %; found 25.3 %) occurred in the temperature as a bis-monodentate ligand to bridge adjacent metal atoms
Z. Anorg. Allg. Chem. 2010, 1629–1634
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Z.-H. Zhang, S.-C. Chen, H. Xu, M.-Y. He, Q. Chen
ARTICLE
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Acknowledgement
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We gratefully acknowledge Jiangsu Province Outstanding Science and
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the financial support. Our special thanks go to Prof. Jianping Lang
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Received: December 20, 2009
Published Online: March 31, 2010
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© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Z. Anorg. Allg. Chem. 2010, 1629–1634