Feature article

Yuji Ohashi

[Yuji Ohashi]Yuji Ohashi was born in Fukui, Japan in 1941 and studied chemistry at the University of Tokyo. After graduating in 1964 he pursued his interest in crystallography under the supervision of Yoshihiko Saito. He became a research associate at the Tokyo Institute of Technology in 1968 and he received his DSc degree from the University of Tokyo based on the structural studies of reaction intermediates.

In 1977 he found that a chiral alkyl group of a cobaloxime complex was racemized on exposure to visible light with retention of the single crystal form. The inversion process of the chiral group was observed directly from changes in the electron density maps during intermediate stages of the reaction. Such a reaction was called crystalline-state reaction to distinguish it from the usual solid state reactions. Not only small alkyl groups but also bulky groups bonded to the cobalt atom were found to isomerize in the crystalline-state on exposure to visible light. A variety of crystals other than cobaloxime complexes also showed a crystallinestate reaction. Recently a variety of unstable species such as radical pairs, triplet carbenes and triplet nitrenes were analyzed by X-rays, since the photo-produced unstable species were kept in the crystal with retention of the crystalline lattice at low temperatures. Moreover, the photo-excited state of the diplatinum complexes was analyzed by X-rays, irradiating the crystal with UV light at low temperatures.

In order to obtain the intensity data more quickly, a new diffractometer with an imaging-plate detector, R-AXIS RAPID, was developed in collaboration with Rigaku. Moreover, a new photon-counting detector, MSGC, is now being developed in collaboration with Prof. Tanimori of Kyoto Univ. in order to collect an entire dataset within one second.

He has been honored by the Crystallographic Society of Japan (1983), the Chemical Society of Japan (2002) and by Harushige Inoue from JST (2002). He has served the scientific community as the Chair of Organic Crystal Committee of the Chemical Society of Japan (2001-2002), Chair of the Japanese National Committee for Crystallography (1994-1997), President of the Crystallographic Society of Japan (1998-1999), President of the Asian Crystallographic Association (1999-2002) and as a member of the IUCr Executive Committee(2002-2005).