Marine phytoplankton and bacteria emit reduced sulfur compounds into the atmosphere. Atmospheric oxidation in the presence of NOx leads to the formation of S-nitrosothiols (RSNOs). These RSNOs can subsequently photodissociate causing a production of NO. In collaboration with Dr. Nathan Kidwell’s laboratory at The College of William and Mary, we are studying the 355 nm photodissociation of nitrosothiophenol. Using velocity map imaging (VMI), the Kidwell lab measures the total kinetic energy released by the photodissociation, and found that S-nitrosothiophenol has two dissociation pathways which differ based on whether or not the thiophenoxy radical (PhS) is electronically excited. Both pathways are fast relative to the rotational period of nitrosotiophenol. We use multi-reference electronic structure approaches to map out the portion of the potential energy surfaces of nitrosothiophenol associated with this photodissociation. We show that the exit channel producing NO with low translational kinetic energy arises from the direct dissociation on the S2 bright state, which produces PhS*. The other exit channel occurs through the nitrosothiophenol undergoing intersystem crossing from S2 and T2, leading to ground state PhS and NO with high translational kinetic energy. We further show that this intersystem crossing occurs through the low-frequency C-S-N-O torsion.

Computational study of competing pathways in the photodissociation of nitrosothiophenol

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.