Christopher A. Zoto, M. Ucak-Astarlioglu, R. Connors
Feb 5, 2016
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0
Influential Citations
13
Citations
Journal
Journal of Molecular Structure
Abstract
Abstract Photochemical studies of (2E,5E)-2,5-bis(4-dimethylaminobenzylidene)-cyclopentanone ( I ) have been carried out. Compound I has been shown to sensitize the production of singlet oxygen ( 1 O 2 ) in deuterated toluene (C 7 D 8 ), chloroform (CDCl 3 ), and methanol (CD 3 OD). Tetramethylethylene (TME) was used as the indicator for 1 O 2 production. Photobleaching of solutions of the dye was observed, which led to an investigation of the chemical reactivity of I with 1 O 2 . Based on 1 H NMR, UV–Visible absorption spectroscopy, and HPLC/MS experimental data, it is proposed that the self-sensitized photooxidation of I with 1 O 2 yields 4-dimethylaminobenzaldehyde and (E)-3-(4-dimethylaminobenzylidene)-1,2-cyclopentadione as products. Photooxidation of I was not detected in CH 3 OH but was found in CD 3 OD. The absence of photooxidation in CH 3 OH is attributed to the short lifetime of singlet oxygen in this solvent (τ Δ = 9.5 μs), compared to its lifetime in CD 3 OD (τ Δ = 270 μs). UV–Visible absorption spectra of irradiated solutions of I in deoxygenated solvents demonstrate that (E,E) → (E,Z) photoisomerization of the dye takes place under these conditions.