Study of novel fluorescent coumarin-3,4-dihydropyrimidin-2(1H)-ones dyads. Estimation of ground- and excited-state dipole moments from a solvatochromic shift

The photophysical properties (ground- and excited-state dipole moments, change in the dipole moment and fluorescence quantum yield) of three coumarin-3,4- dihydropyrimidin-2(1H)-ones dyads in different solvents are characterized. All the properties are solvent-dependent; e.g. dipole moments of the excited-state were higher than those of the ground-state and quantum yields of the molecules vary (9 to 22%) with the change in the solvent polarity.126