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Publication - Professor Andrew Orr-Ewing

    Intermolecular Hydrogen Bonding Controlled Intersystem Crossing Rates of Benzophenone

    Citation

    Venkatraman, RK, Kayal, S, Barak, A, Orr-Ewing, AJ & Umapathy, S, 2018, ‘Intermolecular Hydrogen Bonding Controlled Intersystem Crossing Rates of Benzophenone’. Journal of Physical Chemistry Letters, vol 9., pp. 1642-1648

    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.

    Full details in the University publications repository