J. Phys. IV France 114 (2004) 553
Molecular conductors containing photoreactive speciesT. Naito1, 1, 2, 1, 3, 1 and T. Inabe2
1 Division of Innovative Research, Creative Research Initiative "Sousei" (CRIS), Hokkaido University, Kita 20, Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0020, Japan
2 Division of Chemistry, Graduate School of Science, Hokkaido University, Kita 10, Nishi 8, Kita-ku, Sapporo, Hokkaido 060-0810, Japan
3 Department of Molecular Assemblies, Institute for Molecular Science (IMS), Nishigonaka 38, Myodaiji, Okazaki, Aichi 444-8585, Japan
In order to examine the possibility of (persistent) carrier doping to molecular crystals by light exposure, some different types of molecular crystals containing photoreactive species are synthesized and characterized. The [ Ru(bpy) 3] 2+ cation (bpy = 2,2'-bipyridyl) yielded two different new complexes with [ Ni(dmit) 2] - radical species, both of which were structurally characterized and turned out to be band insulators. Methy viologen (MV) has been found to yield a new phase of the complex with [ Ni(dmit) 2] -, MV[ Ni(dmit) 2] 2. The temperature dependences of electrical resistivity (decreasing with lowering temperature down to 1.0 K) and magnetic susceptibility (Pauli paramagnetism from 300 K to 1.8 K with a hysteresis below 100 K) clearly indicate that this phase is metallic. The thermoelectric power exhibited 0 VK -1 from 300 K-4.2 K. This phase turned out to be metastable, and the crystals gradually turned into insulating ones. The effects of UV-VIS light exposure to the conducting and magnetic properties of Ag(DMe-DCNQI) 2 have been studied, and clear differences between the exposed and the pristine crystals were observed. The ESR signal at 3.7 K suggested that the exposed sample should include the Ag(0) species. Key words. Photoreaction - doping - conductivity.
© EDP Sciences 2004