8-Mercaptoquinoline as a Ligand for Enhancing the Photocatalytic Activity of Pt(II) Coordination Complexes: Reactions and Mechanistic Insights

A family of quinoline–platinum(II) complexes as efficient photocatalysts is presented. Their key characteristic is their easy preparation by coordination of the readily available 8-hydroxy- or 8-thio-quinoline ligands, which are well known for their strong chelating ability to different metal ions. In the different photochemical transformations investigated, such as cross-dehydrogenative coupling, oxidation of arylboronic acids, and asymmetric alkylation of aldehydes, 8-mercaptoquinoline–Pt(II) complex proved to be the most general catalyst. Moreover, quenching experiments showed that, contrary to related methods reported in the literature, these complexes followed an oxidative quenching mechanism in all transformations studied. Besides, simulations performed with high-level ab initio methods of the complexes have helped to understand their photocatalytic activity.