Crystalline-state reaction of cobaloxime complexes by x-ray exposure. 13. A stepwise structure analysis of the concerted process of racemization

Dynamic motion and various reaction paths of cobaloxime complexes in crystalline-state photoreaction

“…The crystal with 3-mpy, 13, as an axial base ligand was also racemized by X-ray exposure, but the process does not belong to any mode of racemization [51]. Figure 21 shows the changes of cell dimensions with exposure time at 293 and 343 K. The space group is P2 1 2 1 2 1 .…”

“…Change of cell dimensions with exposure time for a crystal of 13 at 293 and 343 K. The intensity data were collected at I-VI stages at 293 K and at I 0 to III 0 stages at 343 K. Reproduced from Ohashi et al[51] with permission from the American Chemical Society. Structures of the R-1-ce groups at the stage VI, viewed normal to the cobaloxime plane for: (a) A and (b) B molecules.…”

“…Structures of the R-1-ce groups at the stage VI, viewed normal to the cobaloxime plane for: (a) A and (b) B molecules. Reproduced from Ohashi et al[51] with permission from the American Chemical Society.…”

The generation and behavior of biradical intermediates in crystalline media

“…Our own work [13] has identified several specific non-bonded interactions between the reacting molecule and its nearest lattice neighbors that seem to control the course of certain solid state photorearrangement reactions. Finally, Ohashi et al [14], have reported a particularly intriguing case where the reaction cavity has actually been mapped out in detail using crystal structure data. This concerns the X-ray-induced racemization of a number of optically active cobaloxime complexes.…”

Crystalline-state reaction of cobaloxime complexes by X-ray exposure. 15. Different reactivity between two crystallographically independent molecules

“…In the previous paper, we reported a new type of racemization which belonged to none of the above three classes (Ohashi, Tomotake, Uchida & Sasada, 1986). The crystal, in which the ligand 3-methylpyridine occupies an axial base position, R-ce-3mepy, contains two molecules, A and B, in the P212~2, cell.…”