Chemical Physics Letters, Vol.714, 160-165, 2019
Photoinduced reversible isomerization of 9H-fluorene into 1H-fluorene by means of hydrogen-atom migration and the lowest electronically excited triplet state studied by matrix-isolation FTIR spectroscopy
Photoinduced reversible intramolecular hydrogen-atom migration between 9H-fluorene and 1H-fluorene isolated in an Ar matrix is found by FTIR spectroscopy with an aid of DFT calculation. The forward isomerization from 9H-fluorene to 1H-fluorene occurs upon UV irradiation (lambda >= 295 nm), while the backward isomerization occurs lambda >= 320 nm light irradiation. The less stable isomer, 1H-fluorene, is identified by comparison of the measured IR spectrum with the corresponding simulated spectral pattern obtained at the B3LYP/6-31 + + G(d, p) level. In addition, an IR spectrum of 9H-fluorene in the T-1 state is measured during UV irradiation (lambda >= 275 nm).