Ab initio and perturbation treatment studies in different dielectric media

Using ab initio method and perturbation treatment of the Onsager model we have studied the geometrical and spectroscopic changes due to the reaction field in several carbonyl compounds including succinimide, N-chlorophthalimide, and phthalic anhydride. A very good agreement is observed between the results of the ab initio method and those of the perturbation treatment. It is found that the carbonyl bonds in the molecules investigated elongate and red-shifted CO stretching modes result. Moreover, based on the solvent-induced vibrational Stark effect, the magnitude of the difference dipole moment and the difference polarizability for N–H stretching mode in succinimide are evaluated to be 0.0157 and 0.608 a.u., respectively.