The CASSCF Study Of Trans-formanilide And Trans-formanilide.Ar

Trans-formanilide is one of the simplest aromatic amides and provides a model of the peptide bond. In order to investigate the sensitivity of molecules which are subject to changes in their environment, CASSCF calculations of the S0, S1, D0 states of the trans-formanilide and trans-formanilide. Ar have been performed using Dunning' s cc-PVDZ basis set. The conclusions are as following.1. The optimized structure of trans-formanilide was turned out that that the Ar is on the top of the side chain and is likely to interact significantly with the side chain.2. The excess positive charge was found to be located on the amide side chain in the D0 state of the two molecules. Some structural changes occur in D0←S0 which mainly correspond to displacements along the in-plane bending and side-chain stretching coordinates.3. Ar atom has few effects on the S0 state of the monomer, but has the significant effects on the S1, D0 states.4. The interaction of the D0 state is stronger than that of the S0 and S1 states, because of the shorter distance and smaller A rotational constant.5. The calculated intermolecular vibrational frequencies are in good agreement with the observed results for trans-formanilide. Ar complex.