Abstract:

Three new mixed-ligand cobalt(II) complexes [Na2Co(μ4-btec)(H2O)8]n (1), [Co2(μ2-btec)(bipy)2(H2O)6]·2H2O (2), and [Co2(μ2-btec)(phen)2(H2O)6]·2H2O (3) (H4btec = 1,2,4,5-benzenetetracarboxylic acid, bipy=2,2'-bipyridine, phen=1,10-phenanthroline) were synthesized using hydrothermal and microwave methods after which the products were characterized by single crystal X-ray diffraction. Complex (1) crystallizes in a monoclinic systemwith a C2/m space group, a=1.5690(2) nm, b=0.9550(1) nm, c=0.6102(2) nm, and β=92.78(3)°. Complex (2) belongs to a monoclinic systemand has a P21/n space group, a=1.2290(1) nm, b=0.7594(2) nm, c=1.7920(1) nm and β=100.07(2)°. Complex (3) belongs to a triclinic systemand has a P1 space group, a=0.7454(1) nm, b=1.1072(2) nm, c=1.2177(2) nm, α=108.41(3)°, β=101.94(3)°, and γ=109.03(3)°. All three complexes are bridged by the betc4- ligands to form 3 dimensional (D) (1) and binuclear (2and 3) structures. The betc4- ligands adopt μ4-η2η2η2η2, μ2-η1η1, and μ2-η1η1 coordinated modes in the three complexes, respectively. The hydrogen bonds allow complexes (2) and (3) to be further connected into 2D and 3D networks. The complexes were characterized by IR, UV-visible-near infrared (UV-Vis-NIR), and surface photovoltage spectroscopy (SPS). The SPS of the three complexes (1)-(3) indicate that they all exhibit positive surface photovoltage (SPV) responses from 300 to 600 nm. However, the intensity, position, and number of SPV responses are different, which may be attributed to the differences in their structures and coordination environment of the Co ions in the three complexes. The SPS results are consistent with associated UV-Vis-NIR spectrumresults.

Key words: Photoelectric property, Co(II) complex, Synthesis, Structure