Crystal Structure and Spectroscopic Properties of the CT Complex of Methyl Viologen Dication and o-Dimethoxybenzene Included in a Polycyano−Polycadmate Host and Electrostatic Effects on Its CT Absorption

Abstract

Using the polycyano−polycadmate host that is a negative-charged Cd cyanide complex with a framework structure built with Cd2+ ions and bridging cyanide ligands, we synthesized a clathrate including methyl viologen dication (MV2+) and o-dimethoxybenzene (ODMB) as guests. The color of the clathrate was reddish-brown, and its origin was considered to be a charge transfer (CT) interaction of a CT complex formed with MV2+ as an acceptor and ODMB as a donor in the host. The wavelength at the CT absorption maximum was largely red shifted as compared with that of the CT complex in an acetonitrile solution. The single-crystal X-ray diffraction analysis revealed a π−π stacking structure of the CT complex and a one-dimensional arrangement of the CT complexes in a channel-like cavity of the framework host. In the array of the CT complexes, MV2+ ions are adjacent to each other and their separation is short. The direction of the transition moment of the CT absorption determined from the structural information and the s...