Abstract
The crystal structure of θ-(BEDT-TTF)2RbCo(SCN)4 in its insulating state below TMI (approximately 200 K) was investigated by X-ray diffraction experiments. The transfer integrals between the BEDT-TTF molecules were also calculated from the structural data, and the ionicities of BEDT-TTF molecules were estimated from the intramolecular bond length distribution. A large modulation of transfer integrals and charge disproportionation between BEDT-TTF molecules were found. The ratio of ionicities was 0 to +0.2:+0.8 to +1.0. These results were compared with thoes of the analogous salt θ-(BEDT-TTF)2RbZn(SCN)4.
