Experimental determination of ground and excited state dipole moments of N, N-bis (2, 5-di-tert-butylphenyl)-3, 4:9, 10-perylenebis (dicarboximide) (DBPI) a photostable laser dye.

In the present work, the absorption, emission spectra and dipole moments(μ(g), μ(e)) of N, N-bis (2, 5-di-tert-butylphenyl)-3, 4:9, 10- perylenebis (dicarboximide) (DBPI) have been studied in solvents of various polarities at room temperature. Using the methods of solvatochromism, the difference between the first excited singlet state (μ(e)) and ground state (μ(g)) dipole moments was estimated from Lippert - Mataga,, Bakhshiev, Kawski - Chamma - Viallet equations. The change in dipole moment (Δμ) was also calculated using the variation of the Stokes shift with microscopic solvent polarity parameter (E(T)(N)). It was observed that the value of excited singlet state dipole moment is higher (3.53 Debye) than the ground state one (1.92Debye), showing that the excited state of DBPI is more polar than the ground state.