Hydrogen bond effect on the photophysical properties of 2-ureido-4[1H]-pyrimidinone quadruple hydrogen bonded systems

Abstract

In this work, spectroscopic techniques and quantum chemistry calculations were used to investigate the photophysical properties of 2-ureido-4[1H]-pyrimidinone (UPy) systems in two different solvents of DMSO and DCM. The investigations were carried out on the three UPy systems (AnUP, NaUP and UPNa) with two different choromophores (i.e., anthracene and naphthalene) located at the head and the tail part of the UPy module. In DCM the UPy systems exist as the Keto-2 form that self assembles into a dimer through quadruple H-B arrays AADD–DDAA (solute–solute hydrogen bonds). In DMSO the UPy systems exist in the Keto-1 form which then forms a hydrogen bond complex with the solvent through solute–solvent interaction. The differences in excited state hydrogen bond dynamics and in configuration dynamical processes, account for the measured different fluorescence lifetimes and fluorescence quantum yields (FQY, Φ_F) of the UPy systems studied in this work.