Electronic spectroscopy of the β-carboline derivatives nitronorharmanes, nitroharmanes, nitroharmines and chloroharmines in homogeneous media and in solid matrix

Abstract

Electronic spectra (absorption, fluorescence and phosphorescence emission spectra) of nitro-β- carboline derivatives (nitronorharmanes, nitroharmanes and nitroharmines) in acetonitrile and in methanol solution at 298 K and in solid matrix at 77 K have been recorded and compared with those of the corresponding β-carbolines and chloroharmine derivatives. The electronic absorption spectra of triplet transients of these β-carbolines, the triplet lifetime, τT, and the intersystem crossing quantum yield, φisc, were measured by Laser Flash Photolysis at 298 K. The dynamic properties of the lowest excited singlet and triplet states (τf, τp, φf and φp) have been measured in the same experimental conditions. From these data, the radiative and radiationless rate constants (k o f , kisc and kic) were derived. The intramolecular spin - orbital coupling effect on the spectroscopic data and photophysical rate constant were also analyzed.