Photoisomerization in a platinum-amido pincer complex: An excited-state reaction pathway controlled by localized ligand photochemistry

Computational investigations of the electronic spectroscopy and photochemical isomerization in the complex (bis(8-quinolinyl)amido)PtMe ₂I are presented. Time-dependent density functional theory, in conjunction with the polarizable continuum solvent model, reproduce the experimental spectra for the mer and fac isomers well. The nature of the initially populated states for the mer isomer are pp* in nature and localized on the BQA ligand. Geometry optimization shows that the system relaxes in the excited manifold to a fac-like geometry in the S₁ electronic state. Complete active space self-consistent field (CASSCF) calculations show that there exists a sloped conical intersection that connects the excited- and ground-state fac species, allowing for radiationless deactivation in fac-like geometries. © 2010 American Chemical Society.