engleski

Comparative study of the photodynamics of malonaldehyde and acetylacetone

In this computational study we explore the photodynamics of malonaldehyde and compare it to that of the homologous acetylacetone. Upon photoexcitation to the bright S2(ππ*) state malonaldehyde relaxes to the S1(nπ*)state on an ultrashort time scale. Once in the S1(nπ*) state the population of malonaldehyde splits. Part of the population undergoes internal conversion to the ground state by deplanarization of the H- chelate ring, while the other part crosses to the triplet manifold. The comparison with acetylacetone reveals a substantial increase of the internal conversion pathways, from less than 20% in acetylacetone to 40% in malonaldehyde. We show that the substitution of the aliphatic hydrogens by the methyl groups reduces the accessibility of the S1/S0 conical intersection seam in acetylacetone. The system then crosses to the triplet manifold and homolytic C–CH3 bond cleavage takes place.

malonaldehyde ; photochemistry

nije evidentirano