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Intermolecular Hydrogen Bonding Controlled Intersystem Crossing Rates of Benzophenone

Research output: Contribution to journalArticle

Original languageEnglish
Pages (from-to)1642-1648
Number of pages7
JournalJournal of Physical Chemistry Letters
Volume9
Issue number7
Early online date14 Mar 2018
DOIs
DateAccepted/In press - 14 Mar 2018
DateE-pub ahead of print - 14 Mar 2018
DatePublished (current) - 5 Apr 2018

Abstract

Solvation plays a critical role in various physicochemical and biological processes. Here, the rate of intersystem crossing (ISC) of benzophenone from its S1(nπ∗) state to its triplet manifold of states is shown to be modified by hydrogen-bonding interactions with protic solvent molecules. We selectively photoexcite benzophenone with its carbonyl group either solvent coordinated or uncoordinated by tuning the excitation wavelength to the band center (λ = 340 nm) or the long-wavelength edge (λ = 380 nm) of its π∗ ↔ n absorption band. A combination of ultrafast absorption and Raman spectroscopy shows that the hydrogen-bonding interaction increases the time constant for ISC from <200 fs to 1.7 ± 0.2 ps for benzophenone in CH3OH. The spectroscopic evidence suggests that the preferred pathway for ISC is from the S1(nπ∗) to the T2(ππ∗) state, with the rate of internal conversion from T2(ππ∗) to T1(nπ∗) controlled by solvent quenching of excess vibrational energy.

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    Rights statement: This is the author accepted manuscript (AAM). The final published version (version of record) is available online via ACS publications at https://pubs.acs.org/doi/10.1021/acs.jpclett.8b00345. Please refer to any applicable terms of use of the publisher.

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