Ground state and excited state dipole moments of 6,8-diphenylimidazo[1,2-α]pyrazine determined from solvatochromic shifts of absorption and fluorescence spectra

Electronic absorption and dual fluorescence spectra of 6,8-diphenylimidazo[1,2-α]pyrazine (68DIP) was recorded in various solvents with different polarity at room temperature. The ground state (μg) and the excited state (μg) dipole moments of 68DIP were estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (ɛ) and refractive index (n  ). The results show that the value of excited state dipole moment in SE: μeSE=2.8772 D and twisted intramolecular charge transfer (TICT) excited equilibrated state dipole moment value of μeLE=2.9744 D was found. The solvent dependent spectral shifts in absorption and fluorescence spectra were analyzed by the polarizability–polarity and Kamlet–Taft parameters.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Electronic absorption and dual fluorescence spectra of 6,8-diphenylimidazo[1,2-α]pyrazine (68DIP) was investigated in various solvents with different polarity at room temperature. ► The values of excited state dipole moment and twisted intramolecular charge transfer (TICT) excited equilibrated state dipole moment were determined. ► Fluorescence intensities ratio LE/SE evidences that LE band is not of excimer origin.