Cd (II)–M (II) hetero-nuclear coordination polymers: Synthesis, structure and photo-electric properties (M = Fe, Co, Cd)

Three Cd (II)–M (II) hetero-nuclear coordination polymers, [FeCd2(Hcit)2(H2O)2]n (1), [CoCd2(BTC)2(H2O)4]n (2) and [Cd3(Hcit)2(H2O)2]n (3) (H4cit = citric acid, H3BTC = 1,3,5-benzenetricarboxyl acid), were synthesized through hydrothermal method. They were characterized through elemental analysis, IR spectra, UV–Vis absorption spectra, X-ray powder diffraction, single-crystal X-ray diffraction and surface photovoltage spectra (SPS). Structural analysis indicates that 1 and 3 possess 2D structures, which are further connected to 3D structures by hydrogen bonds. 2 is a 3D Cd–Co coordination polymer bridged by BTC3− groups. The SPS show that 1 and 2 present positive photovoltage response in 300–550 nm, but the photovoltage response of 3 appears in 300–400 nm. It is indicated that the limits of SPS response bands of polymers 1 and 2 are wider than those of 3 because of introduction of the other transition metal ions. There is a good corresponding relationship between SPS and UV–Vis absorption spectra.