Photochemistry of 1,5-Cyclooctadiene Platinum Complexes for Photoassisted Chemical Vapor Deposition

Quantum yields for disappearance of (COD)­PtMe2 (1a) and (COD)­PtMeCl (1b) were determined at 334 nm in C6D6 solvent. Chain reactions initiated by formation of a methyl radical were proposed to be the cause of quantum yields higher than unity (Φ = 5.52 ± 0.40 for 1a) when the reaction mixtures included C4F9I. The chain reactions were suppressed in the presence of the radical trap 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), which resulted in measured disappearance quantum yields of Φ = 0.037 ± 0.003 for (COD)­PtMe2 and Φ = 0.44 ± 0.02 for (COD)­PtMeCl at 334 nm. Weak luminescence was observed for 1a and 1b, and it was determined that emissive decay is not competitive with Pt–CH3 bond homolysis. DFT studies enabled assignment of both SBLCT and MLCT transitions in the UV/vis spectra of 1a, while 1b only exhibits MLCT transitions. These effects can be attributed to the symmetry of the molecule and its electronic structure.