Systematics of the electronic spectra of some substituted and bridged indole derivatives

Abstract

Abstract Many indole derivatives possess desirable scintillation qualities, such as high quantum yield and short decay time. The fluorescence and absorption spectra, fluorescence decay time, quantum yield, the width of each spectrum, and Stokes loss of 14 substituted and bridged analogues of indole in nonpolar (cyclohexane) and polar (ethanol) solutions have been measured. Fluorescence spectra are shifted more toward the red, values of Stokes loss are larger, the molar extinction coefficients are smaller, and the natural fluorescence lifetimes and decay times are longer in ethanol than in cyclohexane solution. In the derivatives of 2-phenyl indoles, the fluorescence transition appears to be allowed and long-axis polarized.