Theoretical studies of the photochemical dynamics of acetylacetone: Isomerzation, dissociation, and dehydration reactions

Abstract

The potential energy surfaces of the C-O cleavage, rotational isomerization, keto-enolic tautomerization, and dehydration reactions of acetylacetone in the lowest triplet and ground states have been determined using the complete active space self-consistent field and density functional theory methods. The main photochemical mechanism obtained indicates that the acetylacetone molecule in the S 2( 1ππ*) state can relax to the T 1( 3ππ*) state via the S 2-S 1 vibronic interaction and an S 1/T 1/T 2 intersection. The C-O fission pathway is the predominant dissociation process in the T 1( 3ππ *) state. Rotational isomerization reactions proceed difficultly in the ground state but very easily in the T 1( 3ππ*) state. Keto-enolic tautomerization takes place with little probability for acetylacetone in the gas phase. © 2006 American Chemical Society.