Study of the electronic structure and spectra of diphenylcarbene conformers in their ground state and lower excited states

The triplet-triplet fluorescence of perprotonated and perdeuterated diphenylcarbene (DPC-h 10 and -d 10 ) in n-hexane at 4.2-25 K are both composed of a sharp spectrum and a broad blue-shifted one. They are attributed to two different conformers, the sharp spectrum corresponding to DPC in a quasi-planar geometry. The excitation spectra of both emissions consist of broad bands with a large Stokes shift. A detailed CS-INDO CI investigation (configuration interaction based on an intermediate neglect differential overlap method adapted to conformation and spectroscopy problems) is performed for three different geometries of DPC having C 2υ , C 2 , and C 1 symmetries