Electrochemical Synthesis, Crystal Structure, and Photomagnetic Properties of a Three-Dimensional Cyano-Bridged Copper−Molybdenum Complex

A single crystal of CsI2CuII7[MoIV(CN)8]4·6H2O was electrochemically prepared on a Pt wire
electrode with a constant potential of +500 mV vs Ag/AgCl electrode. X-ray single-crystal structural analysis
showed that this compound consists of a three-dimensional cyano-bridged Cu−Mo bimetallic assembly
with a tetragonal structure of I4/mmm. The coordination geometry of MoIV is bicapped trigonal prism, and
that of CuII is five-coordinate of square pyramidal or four-coordinate of square planar. This compound was
also prepared as a 0.2−3.0 μm thick film on a SnO2-coated glass in the same electrochemical manner.
When the sample, which shows paramagnetism due to CuII (S = 1/2), was irradiated with 450−500 nm
light at 5 K, spontaneous magnetization with a Curie temperature of 23 K was observed. This photoinduced
change was recovered by a thermal treatment. In the infrared (IR) and electron spin resonance (ESR)
spectra after light irradiation, variations in the stretching IR peak of CN bridged to MoIV and the paramagnetic
ESR peak of CuII were observed, respectively. The data indicate that this photomagnetism is caused by
the electron transfer from MoIV to CuII and the ferromagnetic ordering between CuII (S = 1/2) and MoV (S
= 1/2).