The Electronically Excited-States of 2-Phenylindole

Journal article, 1991

The light absorption of 2-phenylindole (2PI) in the UV region (210-350 nm) is investigated by means of linear dichroism in stretched polyethylene film and fluorescence polarization anisotropy in a propylene glycol glass. Experimentally, 2PI is found to have five distinct electronic transitions located above 200 nm for which the transition moments are determined. The conclusions are supported by quantum chemical calculations and the origin of the so-called composite band is discussed. Comparison with the absorption spectrum of the fluorescent DNA binding probe DAPI is also made and 2PI is found to be an appropriate model system for the electronic transitions of DAPI.