Study of dipole moments of some coumarin derivatives

•Dipole moments for 6HMC and 6MMC are estimated from theoretical and experimental method.•The change in dipole moment estimated experimentally are much less than other family member of coumarin derivatives.•Two different functional group leads to less change in dipole moment comparative to other coumarin derivatives.

In this paper we report the dipole moments of two coumarin derivatives viz 6-methoxy-4-methyl coumarin (6MMC) and 6-hydroxy-4-methyl coumarin (6HMC). Solvatochromic shift in absorption and emission spectra as a function of different solvent polarity parameter has been analyzed. With the help of this, ground and first excited state dipole moments of two coumarin derivatives have been calculated. Dipole moments are also estimated theoretically. The first excited state dipole moment of both the coumarin derivatives is higher than the ground state dipole moment indicating a substantial redistribution of π-electron density in the excited state.