We report a transient resonance Raman spectrum for the 2-fluorenylnitrenium ion obtained after photolysis of 2-azidofluorene. The 10 experimental Raman band frequencies of the transient spectrum show very good agreement with the computed frequencies from BPW91/cc-PVDZ density functional theory calculations for the 2-fluorenylnitrenium ion. Our results confirm the assignment of the approximately 460 nm transient absorption band formed after photolysis 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 character with significant delocalization of the charge over both phenyl rings of the fluorene moiety. We compare our results for the 2-fluoreneylnitrenium ion to those previously reported for several other arylnitrenium ions.

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We present a resonance Raman investigation of the lowest energy dipole-allowed absorption band of [Au 2 (dcpm) 2 ](ClO 4 ) 2 (dcpm ) bis(dicyclohexylphosphine)methane). The resonance Raman spectra provide the first experimental proof of the 5dσ* f 6pσ electronic transition in dinuclear gold(I)-phosphine compounds. A resonance Raman intensity analysis of the spectra allows estimation of the structural changes of the [dσ*pσ] excited states relative to the ground state.

We examine the chemical reaction of isodiiodomethane (CH 2 I-I) with cyclohexene using time-resolved resonance Raman spectroscopy. Our results indicate that CH 2 I-I reacts with cyclohexene to produce an iodine molecule leaving group on the 5-10 ns time scale which then almost immediately forms a I 2 :cyclohexene complex. This in conjunction with previous results from photochemistry experiments and recent density functional theory calculations indicates that isodiiodomethane is the methylene transfer agent mainly responsible for cyclopropanation of olefins when using ultraviolet photolysis of diiodomethane. We present a mechanism for photocyclopropanation that is consistent with both experimental and theoretical characterization of reaction intermediates and products formed after ultraviolet photolysis of diiodomethane in a condensed phase environment. We briefly discuss the differences and similarities in the behavior of the isodiiodomethane and the Simmons-Smith carbenoids toward cyclopropanation reactions with olefins.

Time-resolved resonance Raman spectra for triplet 4-methoxyphenyl nitrene and 4-ethoxyphenyl nitrene and their dimerization reaction to form azo dimer products in acetonitrile solution on the nanosecond time scale are reported. As the 4-methoxyphenyl nitrene and 4-ethoxyphenyl nitrene Raman bands decay, the Raman bands for the azo dimer products increase in intensity. The triplet 4-methoxyphenyl nitrene and 4-ethoxyphenyl nitrene species and their reaction to produce azo products are compared to a recent study of the 2-fluorenyl nitrene species and its reaction to form dehydroazepine ring-expansion products. The properties of the singlet and triplet arylnitrenes and their reaction mechanisms to form azo dimer and ring-expansion products are briefly discussed.