Excited-state hydrogen bonding and deprotonation of esculetin in solution: A DFT/TDDFT study

► A DFT/TDDFT method was used to study the electronic spectral properties of different deprotonated forms of esculetin. ► The minor absorption and fluorescence bands observed at longer wavelengths in experiments were assigned. ► The relationship between electronic spectral shifts and excited-state hydrogen bonding changes was clarified.