Photoejection of electrons from pyrrole into an aqueous environment: Ab initio results on pyrrole-water clusters

Ab initio (RHF, CASSCF and CASPT2) calculations in the ground and lowest excited singlet states have been performed on pyrrole and pyrrole-water clusters. Full geometry optimization in the ¹πσ^* state, which is energetically accessible from the optically allowed ¹ππ^* state, reveals the flow of the electronic charge from pyrrole towards the water molecules, i.e., the formation of a charge transfer-to-solvent state. The computational results indicate that pyrrole-water clusters are good models for the investigation of the mechanistic details of the electron solvation process occurring upon ultraviolet photoexcitation of organic chromophores in liquid water.