A TD-DFT study on the excited-state hydrogen-bonding interactions in the 2-(2-thienyl)-3-hydroxy-4(1H)-quinolone-(H2O)3 cluster

► Hydrogen bonds CO⋯H1O1 in 3HQT monomer and HB-II, HB-III and HB-IV in 3HQT-(H2O)3 cluster are strengthened in state S1. ► Compared with that in 3HQT monomer, hydrogen bond CO⋯H1O1 in 3HQT-(H2O)3 cluster is weakened in both states S0 and S1. ► The two emission bands observed at the short wavelength in experiments are assigned by the TD-DFT calculations.