Photochemistry of matrix-isolated 3-chloro-1,2-benzisoxazole: Generation and characterization of 2-cyanophenoxyl radical and other reactive intermediates

Abstract

Photochemistry of 3-chloro-1,2-benzisoxazole 1 in N2 and Ar matrices at 10 K leads to N-chloro-ketenimine 3 and 2-cyanophenyl-hypochlorite 4. The reaction kinetics and the observed photoisomerization of 3 to 4 indicate that ketenimine 3, possibly formed via an elusive vinylnitrene VN, is an intermediate in the formation of hypochlorite 4. A new pathway involving the formation of 2-cyanophenoxyl radical 5, which was captured only in Ar matrix, was also observed. Radical 5 is possibly formed via photodetachment of Cl atom from 1 (or VN) and might explain the formation of 3-chloro-6-oxocyclohexa-1,4-dienecarbonitrile 2 in N2 and Ar matrices. All the species were characterized by IR spectroscopy and theoretical calculations. The computed geometric and electronic structure of radical 5 is discussed. Overall, the results provided further insight into the mechanism of the photochemistry of 1,2-benzisoxazoles and allowed characterization of new interesting reactive intermediates.