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Excited State Dipole Moment Of New Indole Derivatives By Solvatochromic Shift Method

R.S.Kunabenchi, H.M.Suresh Kumar, S.V.Nishti, J.S.Biradar

The electronic absorption and fluorescence spectra of newly synthesized indole derivatives viz., 1) 5-methyl-3-phenyl–2–[4′–amino-s-triazolo- 3′-yl] indole-5′-hydrazide, (MPATIH) 2) 3-[5′-methyl-3′-phenylindol-2′- yl] -s-triazolo[3,4-b][1,3,4] thiadiazol-6(5H) -thione (MPITTT) and 3) 5-methyl-3-phenyl-2- [s-oxadiazol-2′-thione-5′-yl] indole (MPOTI) have been measured at 1×10-5 M concentration in various solvents at room temperature. The ground state dipole moment (μg) and first excited singlet state dipole moment (μe) have been estimated from solvatochromic shifts of absorption and fluorescence spectra as a function of the dielectric constant (D) and refractive index (n), and also by utilizing the microscopic solvent polarity parameter ( NT E ). These indole derivatives have shown greater dipole moment in the excited state than the ground state. The results indicate that the observed band in these compounds may be attributed to π→ π* transition.