Transient resonance Raman and density functional theory investigation of the 2-fluorenylnitrenium ion

We report a transient resonance Raman spectrum for the 2-fluorenylnitrenium ion obtained after photolysis of 2-azidofluorene. The 10 experimental Rama n band frequencies of the transient spectrum show very good agreement with the computed frequencies from BPW91/cc-PVDZ density functional theory calcu lations for the 2-fluorenylnitrenium ion. Our results confirm the assignmen t of the similar to 460 nm transient absorption band formed after photolysi s of 2-azidofluorene in water/acetonitrile or water solution to the singlet ground electronic state 2-fluorenylnitrenium ion. Our study indicates the 2-fluorenylnitrenium has a large degree of iminocyclohexadienyl cation char acter with significant delocalization of the charge over both phenyl rings of the fluorene moiety. We compare our results for the 2-fluoreneylnitreniu m ion to those previously reported for several other arylnitrenium ions.