Abstract
To investigate the role of the excited triplet state in the deactivation process of 5-hydroxyflavone (5HF), the photophysical process of 5HF was studied by transient absorption, phosphorescence spectroscopies, and semiempirical calculations. The triplet–triplet absorption (T–T) spectra of 5HF and 5-methoxyflavone (5MF) were observed upon direct and triplet-sensitized excitation. The T–T spectrum of 5HF ( λ max=350 nm, τ T=2.8 μs) was different from that of 5MF ( λ max=360 nm, τ T=6.8 μs). Estimations of the triplet energies of 5HF and 5MF by quenching experiments, phosphorescence, and semiempirical (PM3/CI4) calculation revealed that 5HF underwent an intramolecular hydrogen atom transfer and formed the tautomer in the excited triplet state. The triplet energy of the normal form of 5HF was 260 kJ mol −1, while that of the tautomer form (5HF′) was 197 kJ mol −1. The triplet energy of 5MF, the model compound of the normal form of 5HF, was 261 kJ mol −1. The PM3/CI4 calculation supported the experimental observations and suggested that the most stable conformer in the triplet state of 5HF is the tautomer form.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: Journal of Photochemistry and Photobiology A: Chemistry
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
