Crystal structure, photomagnetic and dielectric properties of a cyanido-bridged Cu-Mo assembly film

A film of a cyanido-bridged Cu-Mo assembly CuII2[MoIV(CN)8]center dot 8H2O (CuMo-film) was electrochemically synthesized. Unlike analogs with a formula of MII2[MoIV(CN)8]center dot zH2O (M = Mn, Fe, Co), which show tetragonal crystal structures, the CuMo-film shows a monoclinic structure in the C2/m space group with cell parameters of a = 17.2461 angstrom, b = 11.1681 angstrom, c =11.2618 angstrom, beta = 125.1089 degrees, and V = 1774.44 angstrom 3. Extended X-ray absorption fine structure analysis traced the bond distances around the Cu site as 1.93-2.30 angstrom for Cu-N and 2.01-2.40 angstrom for Cu-O. CuMo-film exhibits photo-switchable magnetization with TC = 18 K and dielectric relaxation related to the hydrogen bond network. The change of activation energy (Ea) of the dielectric relaxation around 157 K (from Ea = 49.9 kJ mol-1 to Ea = 27.3 kJ mol-1 on cooling) suggests that the development of the hydrogen bond network occurs below 157 K.