Picosecond time-resolved infrared study of 2-aminopurine ionisation in solution

Abstract

Two photon ionisation of 2-aminopurine (2AP) has been monitored following 267 nm irradiation in neutral and acidic aqueous solutions using picosecond time-resolved infrared spectroscopy (ps-TRIR). The transient infrared spectra obtained in neutral and acidic conditions show significant differences that are consistent with the formation of different species, namely the 2AP radical cation, 2AP+•, in acidic conditions and the uncharged radical, 2AP•(-H+), in neutral conditions. The ps-TRIR data indicate that deprotonation of 2AP+• in neutral solution takes place within <2 ps following photoionisation. DFT calculations (EDF1/6-31+G*) were used to support the assignment of the intermediates observed in these spectroscopic experiments.