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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Intersystem crossing via higher triplet states in hypericin
Sharan Babu1, Anshuman Bera1, Sivaranjana Reddy Vennapusa1
1School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram, Maruthamala PO, Vithura, Thiruvananthapuram, Kerala, 695551, India. siva@iisertvm.ac.in.
Abstract:
The hypericin molecule is a naturally occurring photosensitizer. The T1 formation after the photoexcitation of this molecule is studied using dynamics simulations. Both the S1-T3 and S2-T6 intersystem crossing pathways are active at the Franck-Condon point. The rate of the S1-T2 intersystem crossing increases from 105 s-1 to 107 s-1 upon the elongation of the intramolecular proton-transfer coordinate. Further, twist angles originate from the peri-site methyl groups and bay-region hydroxyl groups promote a dominant intersystem crossing via S1-T2, S1-T3 and S2-T4 pathways, with the maximum rate reaching up to 108 s-1. Wavepacket simulations reveal the rapid decay of higher-lying triplet states, leading to ultrafast T1 formation.
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