Acta Crystallographica Section B

Structural Science

Volume 58, Part 2 (April 2002)

research papers

Acta Cryst. (2002). B58, 227-232 [ doi:10.1107/S0108768101019346 ]

Modified photoreactivity due to mixed crystal formation. I. Three mixed crystals between isostructural cobaloxime complexes

C. Vithana, H. Uekusa, A. Sekine and Y. Ohashi

Abstract: Three crystals of 2-cyanoethyl cobaloxime complexes with 3-chloropyridine, 3-bromopyridine and 3-methylpyridine as axial base ligands are isostructural to one another. Three mixed crystals were formed between the pairs: (3-bromopyridine)(2-cyanoethyl)cobaloxime-(2-cyanoethyl)(3-methylpyridine)cobaloxime(0.45/0.55);(3-chloropyridine)(2-cyanoethyl)cobaloxime-(2-cyanoethyl)(3bromopyridine)cobaloxime (0.61/0.39); (3-chloropyridine)(2-cyanoethyl)cobaloxime-(2-cyanoethyl)(3-methylpyridine)cobaloxime (0.44/0.56). The X-ray crystal structure analysis revealed that the mixed compounds are also isostructural to the component crystals. It was found from the change in IR spectra that the 2-cyanoethyl groups in the three mixed crystals isomerized to 1-cyanoethyl groups on exposure to a xenon lamp, as observed for the 2-cyanoethyl groups in the component crystals. Rate constants for the three mixed and three component crystals, measured under the same conditions, are approximately the same, as the reaction cavities for the 2-cyanoethyl groups in the six crystals have almost the same size. For the mixed crystal between 3-chloropyridine and 3-methylpyridine complexes, the isomerization proceeded with retention of the single-crystal form. The conformation and configuration of the 1-cyanoethyl group that was produced were well explained by the shape of the reaction cavity before irradiation.


	Structure factor file (CIF format) (223.6 kbytes) Contains datablock Mix-I

	Structure factor file (CIF format) (222.8 kbytes) Contains datablock Mix-II

	Structure factor file (CIF format) (224.4 kbytes) Contains datablock Mix-IIprime

	Structure factor file (CIF format) (224.9 kbytes) Contains datablock Mix-III

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