Luminescent properties of chalcone and its aminoderivatives

Excitation energies of singlet and triplet π π ⁎ and n π ⁎ transitions are calculated for chalcone and its aminoderivatives using quantum chemical approach. Solvent impact on the molecular geometry and excited state energies is investigated. Both universal (dipole-dipole) and specific (H-bond formation with C O group) interactions are taken into account. Dipole–dipole interactions are shown to stabilize the excited S π π ⁎ state in the systems studied in the same way as for others heteroaromatic luminophores. Specific interactions in protic solvents cause in addition significant geometry deformation to the non-planar structure of the chromophore. Large intramolecular spin–orbit coupling between the lowest singlet and triplet excited states in the latter case is revealed. It proves that intersystem crossing between these states should be the main channel of fluorescent quenching of 4-( N , N ′ - dimethylamino )-chalcone in protic solvents.