A theoretical study of the CX2N radicals (X = F, Cl, Br): the effect of halogen substitution on structure, isomerization, and energetics.

Structural isomers of the CX(2)N radicals, where X = F, Cl, and Br, have been investigated at high level of theory, i.e., using the coupled-cluster method in conjunction with correlation-consistent basis sets ranging in size from triple- to sextuple-zeta. Extrapolation to the complete basis-set limit as well as core-correlation effects and inclusion of higher excitations in the cluster operator have been considered for accurately evaluating geometries and energies. The effect of halogen substitution on molecular structure, isomer stability, and dissociation energy is addressed; in particular, only the F(2)CN, Cl(2)CN, Br(2)CN, and F(2)NC radicals of C(2V) symmetry are predicted to be stable with respect to dissociation.