Room-temperature thermally induced relaxation effect in a two-dimensional cyano-bridged Cu-Mo bimetal assembly and thermodynamic analysis of the relaxation process

Abstract

We observed a photo-switching effect in CuII(1,4,8,11- tetraazacyclodecane)2MoIV(CN)8·10H 2O by irradiation with 410-nm light around room temperature using infrared spectroscopy. This photo-switching is caused by the photo-induced charge transfer from MoIV to CuII. The photo-induced phase thermally relaxed to the initial phase with a half-life time of 2.7 × 101, 6.9 × 101, and 1.7 × 102 s at 293, 283, and 273 K, respectively. The relaxation process was analyzed using Hausers equation, k k0exp-(Ea Ea γ) kBT, where k is the rate constant of relaxation, k0 is the frequency factor, Ea is the activation energy, Ea is the additional activation energy due to the cooperativity, and γ is the fraction of the photo-induced phase. k0, Ea, and E a were evaluated as 1.28 × 107 ± 2.6 s -1, 4002 ± 188 cm-1, and 546 ± 318 cm -1, respectively. The value of Ea is much larger than that of the relaxation process for the typical light-induced spin crossover effect (Ea ≈ 1000 cm-1). Room-temperature photo-switching is an important issue in the field of optical functional materials. The present system is useful for the demonstration of high-temperature photo-switching material. © 2013 © 2013 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution 3.0 Unported License. © 2013 Authors.