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Time‐Resolved Resonance Raman Spectroscopy and Density Functional Study of 2‐Fluorenylnitrene and Its Dehydroazepine Products
Author(s) -
Ong Shing Yau,
Zhu Peizhi,
Poon Yuen Fan,
Leung King Hung,
Fang WeiHai,
Phillips David Lee
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020503)8:9<2163::aid-chem2163>3.0.co;2-c
Subject(s) - raman spectroscopy , singlet state , resonance (particle physics) , resonance raman spectroscopy , chemistry , protonation , photochemistry , photodissociation , spectroscopy , density functional theory , ion , ion laser , excited state , computational chemistry , atomic physics , physics , organic chemistry , optics , quantum mechanics
We report time‐resolved resonance Raman spectra for 2‐fluorenylnitrene and its dehydroazepine products acquired after photolysis of 2‐fluorenylnitrene in acetonitrile. The experimental Raman band frequencies exhibit good agreement with the calculated vibrational frequencies from UBPW91/cc‐PVDZ density functional calculations for the singlet and triplet states of the 2‐fluorenylnitrene as well as BPW91/cc‐PVDZ calculations for the two dehydroazepine ring‐expansion product species. The decay of the 2‐fluorenylnitrene Raman signal and the appearance of the dehydroazepine products suggest the presence of an intermediate species (probably an azirine) that does not absorb very much at the 416 nm probe wavelength used in the time‐resolved resonance Raman experiments. Comparison of the singlet 2‐fluorenylnitrene species with the singlet 2‐fluorenylnitrenium ion species indicates that protonation of the nitrene to give the nitrenium ion leads to a significant enhancement of the cyclohexadienyl character of the phenyl rings without much change of the C−N bond length.