A COMPARATIVE-STUDY OF THE ENERGETICS, STRUCTURES, AND MECHANISMS OF THE HCN[--]HNC AND LICN[--]LINC ISOMERIZATIONS

The potential energy surfaces of the HCN<->HNC and LiCN<->LiNC isomeri zation processes were determined by ab initio theory using fully optim ized triple-zeta double polarization types of basis sets. Both the MP2 corrections and the QCISD level of calculations were performed to cor rect for the electron correlation. Results show that electron correlat ion has a considerable influence on the energetics and structures. Ana lysis of the intramolecular bond rearrangement processes reveals that, in both cases, H (or Li+) migrates in an almost elliptic path in the plane of the molecule. In HCN<->HNC, the migrating hydrogen interacts with the in-plane pi,pi orbitals of CN, leading to a decrease in the C-N bond order. In LiCN<->LiNC, Li+ does not interact with the corresp onding pi,pi orbitals of CN.