Benzophenone, the parent of the diarylketone family, is a versatile compound commonly used as a UV blocker. It may also trigger triplet-based DNA photosensitization. Therefore, benzophenone is involved in DNA photodamage induction. In the absence of experimentally resolved structure, the mechanism of DNA damage production remains elusive. Employing a hybrid quantum mechanics/molecular mechanics approach, here we address the spin transfer mechanism between this drug and proximal thymine, that is, the DNA nucleobase most prone to suffer triplet damages.

An implementation of real-time time-dependent Hartree–Fock (RT-TDHF) and current density functional theory (RT-TDCDFT) for molecules in strong uniform magnetic fields is presented. In contrast to earlier implementations, the present work enables the use of the RT-TDCDFT formalism, which explicitly includes field-dependent terms in the exchange–correlation functional. A range of current-dependent exchange–correlation functionals based on the TPSS functional are considered, including a range-separated variant, which is particularly suitable for application to excited state calculations. The performance of a wide range of propagator algorithms for real-time methods is investigated in this context. A recently proposed molecular orbital pair decomposition analysis allows for assignment of electronic transitions, providing detailed information about which molecular orbitals are involved in each excitation. The application of these methods is demonstrated for the electronic absorption spectra of N 2 and H 2 O both in the absence and in the presence of a magnetic field. The dependence of electronic spectra on the magnetic field strength and its orientation relative to the molecule is studied. The complex evolution of the absorption spectra with magnetic field is rationalized using the molecular orbital pair decomposition analysis, which provides crucial insight in strong fields where the spectra are radically different from their zero-field counterparts.

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We report a computational investigation of the hydrogen abstraction (H-abstraction) induced by triplet benzophenone ((3)BP) on thymine nucleobase and backbone sugar. The chemical process is studied using both high level multiconfigurational perturbation and density functional theory. Both methods show good agreement in predicting small kinetic barriers. Furthermore the behavior of benzophenone in DNA is simulated using molecular dynamics and hybrid quantum mechanics/molecular mechanics methods. The accessibility of benzophenone to the labile hydrogens within B-DNA is demonstrated, as well as the driving force for this reaction. We evidence a strong dependence of the H-abstraction with the non-covalent BP-DNA interaction mode, and a reaction that is less favorable when embedded in DNA than for the isolated system.