Synthesis, structure and surface photovoltage of a series of NiII coordination polymers

Three novel Ni-II coordination polymers [Ni-2(HCOO)(4-)(H2O)(4)](n) (1), [Na2Ni(btec)(H2O)(8)](n), (2; H(4)btec = 1,2,4,5-benzenetetracarboxylic acid) and [{Ni(pdc)(H2O)(2)}center dot H2O](n) (3; H(2)pdc = pyridine-2,5-dicarboxylic acid) have been hydrothermally synthesized and their structures determined by single-crystal X-ray diffraction. The formate groups in complex 1 bridge the Ni-II ions to form a infinite 3D structure. Complex 2 also possesses a infinite 3D structure and the coordination environment of the Ni-II ion is a perfect octahedron. Complex 3 is a 2D infinite coordination polymer. The surface photovoltage spectra of complexes 1-3 indicate that they all show three positive surface photovoltage (SPV) responses in the range of 300-800 nm and all show p-type semiconductor characteristics. Although the intensities of the SPV responses are obviously different, this can mainly be attributed to the difference of their structures. The field-induced surface photovoltage spectra (FISPS) of complexes 1-3 confirm their p-type semiconductor characteristics. ((c) Wiley-VCH Verlag GmbH & Co. KGdA, 69451 Weinheim, Germany, 2006)