Research output: Contribution to journal › Article › peer-review
Competition of singlet and triplet recombination of radical pairs in photoreactions of carboxy benzophenones and aromatic amino acids. / Morozova, Olga B.; Sherin, Peter S.; Yurkovskaya, Alexandra V.
In: Physical Chemistry Chemical Physics, Vol. 21, No. 4, 28.01.2019, p. 2017-2028.Research output: Contribution to journal › Article › peer-review
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TY - JOUR
T1 - Competition of singlet and triplet recombination of radical pairs in photoreactions of carboxy benzophenones and aromatic amino acids
AU - Morozova, Olga B.
AU - Sherin, Peter S.
AU - Yurkovskaya, Alexandra V.
PY - 2019/1/28
Y1 - 2019/1/28
N2 - Time-resolved chemically induced dynamic nuclear polarization (CIDNP) and transient absorption (TA) were applied to reveal the branching ratio of the singlet and triplet recombination channels in the reaction of short-lived radicals of carboxy benzophenones and the aromatic amino acids histidine, tryptophan, and tyrosine in neutral aqueous solution. It was established that the share of triplet recombination increases with increasing number of carboxylic groups: no triplet recombination was found for 4-carboxy benzophenone, whereas ∼13% of radicals of 4,4′-dicarboxy benzophenone (DCBP) and ∼27% of radicals of 3,3′,4,4′-tetracarboxy benzophenone (TCBP) react with histidine radicals from the triplet state of radical pairs. The main idea is that the protonated (π,π∗) triplet state of TCBP or DCBP is populated via back electron transfer from the ketyl radical of TCBP or DCBP to the radical of the amino acid. The protonated triplet state of the ketone decays with the formation of a metastable hydroxylated product, which is detected by TA. Taking into account triplet recombination provides excellent coincidence between experimental data and the simulated CIDNP kinetics.
AB - Time-resolved chemically induced dynamic nuclear polarization (CIDNP) and transient absorption (TA) were applied to reveal the branching ratio of the singlet and triplet recombination channels in the reaction of short-lived radicals of carboxy benzophenones and the aromatic amino acids histidine, tryptophan, and tyrosine in neutral aqueous solution. It was established that the share of triplet recombination increases with increasing number of carboxylic groups: no triplet recombination was found for 4-carboxy benzophenone, whereas ∼13% of radicals of 4,4′-dicarboxy benzophenone (DCBP) and ∼27% of radicals of 3,3′,4,4′-tetracarboxy benzophenone (TCBP) react with histidine radicals from the triplet state of radical pairs. The main idea is that the protonated (π,π∗) triplet state of TCBP or DCBP is populated via back electron transfer from the ketyl radical of TCBP or DCBP to the radical of the amino acid. The protonated triplet state of the ketone decays with the formation of a metastable hydroxylated product, which is detected by TA. Taking into account triplet recombination provides excellent coincidence between experimental data and the simulated CIDNP kinetics.
KW - TIME-RESOLVED CIDNP
KW - LASER FLASH-PHOTOLYSIS
KW - 3,3',4,4'-BENZOPHENONE TETRACARBOXYLIC ACID
KW - ELECTRON-TRANSFER
KW - AQUEOUS-SOLUTION
KW - ION PAIRS
KW - KINETICS
KW - TYROSINE
KW - PHOTOOXIDATION
KW - 2,2'-DIPYRIDYL
UR - http://www.scopus.com/inward/record.url?scp=85060393611&partnerID=8YFLogxK
U2 - 10.1039/c8cp06760k
DO - 10.1039/c8cp06760k
M3 - Article
C2 - 30633277
AN - SCOPUS:85060393611
VL - 21
SP - 2017
EP - 2028
JO - Physical Chemistry Chemical Physics
JF - Physical Chemistry Chemical Physics
SN - 1463-9076
IS - 4
ER -
ID: 18486064