Synthesis, Structure and Electric Property of a 3D Supramolecular CoII Coordination Complex①

SHEN Wei XIAO Xun-Wen YE Fen-Xi WANG Ming-Jun WEN Yi-Hng

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Synthesis, Structure and Electric Property of a 3D Supramolecular CoIICoordination Complex①

SHEN Weia, bXIAO Xun-Wena②YE Fen-XiaaWANG Ming-JunaWEN Yi-Hangc②

a(710064)b(315211)c(321004)

crystal structure, TTF, hydrogen bond, Co complex;

1 INTRODUCTION

Coordination polymer (CP) is one of the research hotspots in coordination chemistry due to its fasci- nating coordination architectures, properties and potential applications[1-3]. Recently, one of the exci- ting research progresses for CP materials is using functional molecules as linker ligands to construct materials with redox-active properties[4]. The incur- poration of redox-active ligands into coordination frameworks offers an effective strategy for the synthesis of redox controllable CP networks. And researchers pay much attention to design suitable organic ligands to construct new coordination polymers. Tetrathiafulvalene (TTF) and its deriva- tives have a sulfur-rich conjugated core and show two reversible oxidation states, which could act as an effective linker to construct new redox-active materials[5]. Many efforts have been made to modify the TTF molecule with functional group, especially on the pyridine-based TTF derivatives[6]. 2,6- Bis(4?-pyridyl)-tetrathiafulvalene, an extended con- jugated analogue of 4,4?-bipyridine, was used in coordination with transition-metal ions to create coordination polymers (CP) or MOF materials[7]. And a Cu+compound with an 8-fold interpenetra- tion dia-like structure showed redox-active and photoelectric properties were reported by Dai’ group[8]. In this work, a new hybird organic-inor- ganic material contains CoII, 4-py-TTF-4-py and H2O, capped by 4-(4-carboxyphenyl)diazenyl)ben- zoate ligand through extensive hydrogen-bonding interaction was reported. In addition, we also reported the electrical conducting property of 1, and a semiconducting behavior was observed in compound 1.

2 EXPERIMENTAL

All reagents were of analytical grade and used as received. The TTF compound 4-py-TTF-4-py L1 was synthesized according to the literature[7]. Electrical conductivity of 1 was measured on a single crystal in the temperature region of 150～294 K. Four gold electrodes (15?) were contacted with a gold paste in parallel with the largest plane of the crystals.

2.1 Synthesis of [Co(C16H10N2S4)2(H2O)4](C14H9N2O4)2 1

2.2 Structure determination

X-ray diffraction data were collected on an Agilent G8910A CCD diffractometer with a gra- phite Mo-radiation (= 0.71073 ?). The software of CrysAlisPro Agilent Technologies was used for collecting the frames of data, indexing the reflections, and determining the lattice constants, absorption correction and data reduction[9]. The structure was solved by direct methods and succes- sive Fourier difference synthesis (SHELXS-97)[10], and refined by full-matrix least-squares method on2(SHELXTL-2014)[11]. All non-hydrogen atoms were refined anisotropically. The pyridine ring of 4-py-TTF-4-py ligand was treated as a disordered group. Hydrogen atoms attached to carbon atoms were refined using the riding-model approximation (iso(H) = 1.2eq(C) and C–H = 0.93 ?). Hydrogen atoms attached to carboxylic oxygen atom and water H atoms were located and refined with distance restraints of O–H = 0.82(2) ? and H–H = 1.30(2) ?, with displacement parameters set at 1.2eq(Owater) or 1.5eq(Ocarboxylic). For 1, a total of 5181 reflections were collected in the range of 3.08≤≤25.50°, of which 3936 were independent. The final= 0.0411 and= 0.0810 (1/[2(F2) + (0.0352)2+ 0.1493], where= (F2+ 2F2)/3),= 1.006, (Δ/max= 0.002, (Δ)max= 0.338 and (Δ)min= –0.289 e·?-3. Selected bond lengths and bond angles of 1 are shown in Table 1.

Table 1. Selected Bond Lengths (?) and Bond Angles (°)

Symmetry code:i: 2–, –, –

Table 2. Hydrogen Bond Lengths (?) and Bond Angles (°)

Symmetry codes: (a) ?+2, ?+1, ?; (b),?1,; (c)+1,?1,; (d) ?, ?+1, ?+1; (e)?1,,; (f) ?+1, ?+1, ?+1

3 RESULTS AND DISCUSSION

3.1 Structure analysis

The asymmetric unit of the title complex contains one-half of the complex cation with the CoIIion located on an inversion center, and a 4-(4-carboxy- phenyl)diazenyl)benzoate counter anion. As shown in Fig. 1, the Co atom has a N2O4octahedral coordination. Four water O atoms in the equatorial plane around the CoIIion (Co–O = 2.0890(17) and 2.114(2) ?) form a slightly distorted square-planar arrangement, and the distorted octahedral geometry is formed by the two N atoms (Co–N = 2.146(2) ?) from two 4-py-TTF-4-py ligands. Thus the cobalt(II) ion is six-coordinated and has octahedral coor- dination geometry. The central plane A (Co(1), O(1), O(2), O(1)i, O(2)i) is planar and plane B (Co(1), N(1), C(1), C(2), C(3), C(4), C(5)) is almost planar with r.m.s deviation of 0.054(21) ?. And the dihedral angle between planes A and B is 86.75(9)°, indicating slight distortion of the octahedral coor- dination sphere around the Co(II) center. The TTF unit in the 4-py-TTF-4-py ligand adopts a boat conformation, as usually observed in the neutral TTF derivatives[12]. All bond lengths and bond angles in the TTF fragment are within the ranges for a neutral TTF molecule[13].

Fig. 1. Molecular structure of the title compound, showing atomic numbering scheme for non-C atoms. Displacement ellipsoids are drawn at the 50% probability level. Symmetry code: (i) 2–, –, –

In the crystal structure, the counter anion, 4-(4- carboxyphenyl)diazenyl)benzoate and one car- boxylate are linked by O–H···N hydrogen bonds with uncoordinated pyridine of 4-py-TTF-4-py ligand, and this O–H···N hydrogen bond is usually found supramolecular synthon in crystal enginee- ring involving a carboxylic acid and a pyridine system. And another deprotonation carboxylate is connected with two coordinated H2O by four O–H···O hydrogen bonds (Table 2), and formed a three-dimensional (3D) network (Fig. 2). These are short contacts (S2···S3 = 3.433(3) ?) in the cation layer to stabilize the crystal structure. Furthermore, the inter-ring···interations between the pyridine ring from 4-py-TTF-4-py ligands and the benzene ring from 4-(4-carboxyphenyl)diazenyl)benzoate (g···g = 3.384(4) ?) to stabilize the crystal structure .

3.2 Characterization of electrical conductivities

The electrical conductivity measured on the single crystals of 1 was 0.04 S·cm-1at room temperature. Upon cooling, the electrical resistivity increases slightly with temperature and then increases sharply below 180 K. Complex 1 exhibits semiconducting behavior in the temperature region measured and the activation energy was estimated to be 120 meV, as shown in Fig. 3. Very interes- tingly, even the TTF unit in 1 is in the neutral state, 1 shows high conductivity at room temperature without external manipulation. The abundant hydrogen bonds, short S···S contact and many atomic contacts between the layers result that compound 1 is highly conductive at room tempe- rature and shows a semiconducting behavior.

Fig. 2. View of the crystal packing along theaxis for the title compound, showing a 3D supramolecular network. The H atoms of aromiatic rings and disordered pyridine rings are omitted for clarity

Fig. 3. Temperature dependence of normalized resistivity (r/rrt) of 1

4 CONCLUSION

In summary, a new coordination compound has been synthesized under hydrothermal condition. It displays a three-dimensional supramolecular network by distinctive O–H···N hydrogen bonds, and stabilized by specific O–H···O hydrogen bonds. Furthermore, the inter-ring···interactions as well as S···S interactions stabilize the crystal structure. Moreover, compound 1 exhibits a semiconducting behavior and may be a good candidate to construct materials with redox-active properties.

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19 March 2018;

11 May 2018 (CCDC 1829537)

① This work was supported by the National Natural Science Foundation of China (21372136) and Ningbo Natural Science Foundation 2015A610126

E-mails: xunwenxiao@nbut.edu.cn and wyh@zjnu.edu.cn

10.14102/j.cnki.0254-5861.2011-2009