Electronic transitions and ESIPT kinetics of the thienyl-3-hydroxychromone nucleobase surrogate in DNA duplexes: a DFT/MD-TDDFT study.

The fluorescent nucleobase surrogate M (2-thienyl-3-hydroxychromone fluorophore) when imbedded in DNA opposite an abasic site exhibits a two colour response highly sensitive to environment changes and base composition. Its two colour emission originates from an excited state intramolecular proton transfer (ESIPT), which converts the excited normal N* form into its T* tautomer. To get deeper insight on the spectroscopic properties of M in DNA duplexes, quantum chemical calculations were performed on M stacked with different base pairs in model trimers extracted from MD simulations.