Synthesis, crystal structure and surface photo-electric property of a series of Co(II) coordination polymers and supramolecules

Four new Co(II) coordination complexes, [Co(o-phta)(pz)2]n 1, [Co(PTA)2(Imh)2]·(HPTA)·H2O 2, {[Co(pdc)2(H2O)]·(ppz)·2H2O}n 3, [K2Co2(ox)(btec)(CH3OH)2]n 4, (H2phta = o-phthalic acid, pz = pyrazole, HPTA = p-toluic acid, ppz = piperazine, Imh = imidazole, H2pdc = pyridine-2,5-dicarboxylic acid, H2(ox) = oxalic acid, H4btec = 1,2,4,5-benzenetetracarboxylic acid), were hydrothermally synthesized and characterized by X-ray single crystal diffraction, IR, UV–Vis absorption spectrum, TG analysis and elemental analysis. The surface photovoltage properties of the four Co(II) complexes were investigated by the surface photovoltage spectroscopy (SPS). The structural analyses indicate that complexes 1 and 3 are 1D coordination polymers and complex 2 is a mononuclear molecular complex. Complexes 1, 2 and 3 are connected into 2D supramolecules by hydrogen bonds, respectively. Complex 4 is a coordination polymer with 3D structure, exhibiting a 4-nodal(4,5,6,12)-connected topology with a Schläfli symbol of (410)2(424·632·810)(45·6)2(49·65·8). The results of SPS show the four complexes exhibit obvious photovoltaic responses in 300–800 nm, which indicates they all possess photo-electric conversion properties. By the comparative analysis of the SPS, it is found that structure of the complex, species of ligand and coordination micro-environment of the Co(II) ion affect the SPS. The relationships between SPS and UV–Vis absorption spectra are discussed.