Excited states dissociation dynamics of indole-x-carboxaldehyde (x = 4, 5, 6, 7): Theoretical and experimental study

Abstract

Excited state dissociation dynamics of indole-x-carboxaldehyde (x = 4, 5, 6, 7) has been investigated by ab initio calculations and photodissociation in a molecular beam at 193 nm using multimass ion imaging techniques. It was found that dissociation processes strongly depends on the position of HCO functional group. Fast component of H atom elimination in the photofragment translational energy distribution suggesting that dissociation occurs in a repulsive excited state, is quite intense for all isomers excluding indole-7-carboxaldehyde, which H atom elimination channel is almost quenched. However, this is the only isomer having intramolecular hydrogen bonding between NH and HCO groups. Ab initio calculations of the excited states potential energy surfaces (PES) demonstrate that the additional low lying conical intersection between S1 and S0 states is expected for the isomer with intramolecular hydrogen bond, which provides fast radiationless relaxation into the S0 state without loss of the H atom.