Photochromism and Molecular Configuration of 2, 3-Epoxy-2, 3-dihydro-2, 3-diphenyl-1H-indenone Study by Resonance Raman and IR Spectroscopy

Abstract

The photoactivated red species produced by UV irradiation of 2, 3-epoxy-2, 3-dihydro-2, 3-phenyl-1H-indenone (DPIO) has been studied by resonance Raman and IR spectroscopy. Taman bands at 1737 cm^-1 (IR band at 1730 cm^-1) and 1210 cm^-1 (IR band at 1210 cm^-1)f DPIO, which are assigned to the C=O stretch and epoxy ring-breathe, respectively, isappear upon irradiation with UV light, and instead, new bands at 1567 cm^-1 (IR bandt 1570 cm^-1) and 1256 cm^-1 (IR band at 1260 cm^-1) are observed. The spectral change is aterpreted in terms of valence tautomerisation as being due to heterolytic cleavage of the C-C bond of the epoxy ring to form zwitterionic 2, 3-diphenyl-2-benzopyrylium-4-olate (DBPO). the bands at 1567 and 1256 cm^-1 are attributed to the conjugated C-0- stretch and he pyrylium ring-breathe (main contribution from the conjugated C=O+-C symmertric tretch), respectively.