Single crystal neutron diffraction study of a crystalline-state photoisomerization in a 3-cyanopropyl cobaloxime complex

Ohara, Takashi   ; Kiyanagi, Ryoji  ; Oikawa, Kenichi   ; Kawasaki, Takuro   ; Kaneko, Koji   ; Tamura, Itaru  ; Nakao, Akiko*; Hanashima, Takayasu*; Munakata, Koji*

Single crystal neutron structure analysis is a powerful tool to study crystalline-state reactions because of its ability to distinguish deuterium atoms from hydrogen atoms. When the hydrogen atoms in specific positions of the reactive group are exchanged with deuterium atoms and the crystalline-state reaction proceeds, the hydrogen/deuterium migration in the reaction is easily observed by the neutron diffraction analysis and consequently the reaction mechanism is estimated. We performed a neutron diffraction measurement of a partially deuterated cobaloxime complex by a TOF-Laue type diffractometer SENJU at J-PARC. The result of the structure refinement showed that the chiral H-C*-D methylene group in the compound has the racemic form. This indicates that the olefin formation and the racemization of the H-C*-D methylene group occurred after the 1-cyanopropyl group was formed by continuous photo-irradiation.