The Nearly Degenerate Triplet Electronic Ground State Isomers of Lithium Nitroxide

Abstract

The triplet electronic ground state potential energy surface of lithium nitroxide has been systematically investigated using convergent quantum mechanical methods. Equilibrium structures and physical properties for five stationary points (three minima and two transition states) have been determined employing highly correlated coupled cluster theory with four correlation-consistent polarized-valence (cc-pVXZ and aug-cc-pVXZ, X = T and Q) and two core correlation-consistent polarized-valence (cc-pCVXZ, X = T and Q) basis sets. The global minimum, roughly L-shaped Li-O-N, is predicted to lie 6.5 kcal mol-1 below the linear LiON minimum and 2.4 kcal mol-1 below the linear LiON minimum. The barrier to isomerization from the global minimum to LiON was found to be 7.4 kcal mol-1 and with regard to LiNO 6.9 kcal mol-1. The dissociation energies, D0, with respect to Li + NO, have been predicted for all minima and for the global minimum was found to be 34.9 kcal mol-1.