Three new mixed-ligand cobalt(II) complexes, [Co(μ4-btec)0.5(phen)(H2O)]n (1), [Co2(μ4-btec)- (bipy)2(H2O)2]n (2) and [Co2(μ2-btec)(phen)2(H2O)4] (3) (phen＝1,10-phenanthroline, bipy＝2,2’-bipyridine, H4btec＝1,2,4,5-benzenetetracarboxylic acid) have been hydrothermally synthesized and characterized by single crystal X-ray diffraction. Complex 1 crystallizes in the monoclinic system, with P2(1)/c space group, a＝1.03364(4) nm, b＝1.05089(4) nm, c＝1.34413(7) nm, β＝105.8610(16)°; complex 2 belongs to triclinic system, P-1 space group, with a＝0.75689(8) nm, b＝0.89882(7) nm, c＝1.06594(12) nm, α＝80.325(7)°, β＝73.092(5)°, γ＝77.077(3)°; and complex 3 also belongs to triclinic system, P-1 space group, with a＝0.64331(13) nm, b＝0.99762(14) nm, c＝1.19864(17) nm, α＝84.193(6)°, β＝76.246(3)°, γ＝85.304(4)°. These three complexes are all bridged by the betc4－ ligands to form 2D, 1D and dinuclear structures. But the coordination modes of the betc4－ respectively adopt μ4-η1η2η1η2, μ4-η1η1η1η1, and μ2-η1η1η1η1 in the three complexes. The existence of hydrogen bonds and π…π type interactions make the complexes further connected to three-dimensional networks. The complexes were characterized by IR, UV-Vis-NIR and surface photovoltage spectra (SPS). The SPS of complexes 1～3 indicate that they all exhibit positive surface photovoltage (SPV) responses in the range of 300～600 nm. However, the intensity, position and numbers of SPV responses are different. The distinctions can be mainly attributed to their structures and coordination environments of the Co ions in the three complexes. Their SPS spectra were found to be basically agreed with their UV-Vis-NIR.

Key words: Co(II) complex, synthesis, structure, photo-electric property