Excited State Processes in Non-Planar and Radical Elaborated Intramolecular Charge Transfer Complexes
Start Date
8-11-2017 8:30 AM
End Date
8-11-2017 12:30 PM
Abstract
Control of molecular excited state processes is important for understanding how to fully realize the potential of molecules in photonics and electronics fields. In order to obtain insight into spin and vibronic level control of excited state lifetimes, we have initiated a study of new diimine platinum(II) dichalcogenolenes that possess charge-separated dichalcogenolene → diimine excited states. Square planar (dichalcogenolene)Pt(diimine) complexes have garnered considerable interest due to their rich photochemical properties and their bright photoluminescence behavior. We have used a combination of electronic absorption and transient spectroscopies, spectroscopic calculations, and group theoretical arguments to understand the remarkable dependence of excited state lifetimes on the nature of the heteroatom donors of the dichalcogenolene ligand, and static distortions in the acceptor ligand that lower the symmetry of the complex and destroy planarity. Our results indicate that anisotropic covalency and low-symmetry distortions control spin orbit and vibronic spin orbit coupling, and these are the origin of enhanced T1→S0 intersystem crossing in these systems. The (dithiolene)Pt(biquinoline) system possesses a T1 → S0 lifetime that is nearly two orders of magnitude less than that observed for planar (dithiolene)Pt(bipyridine). This is due to a strong static distortion driven spin-orbit coupling contribution that can be used to evaluate vibronic spin orbit coupling contributions to the T1 → S0 lifetimes in other (dichalcogenolene)Pt(diimine) complexes. New molecular frameworks that employ persistent radicals coordinated to Pt have recently been synthesized. We discuss their unique electronic structures, which have been probed by spectroscopic and computations studies, in order to understand the excited state dynamics of radical elaborated chromophores.
Excited State Processes in Non-Planar and Radical Elaborated Intramolecular Charge Transfer Complexes
Control of molecular excited state processes is important for understanding how to fully realize the potential of molecules in photonics and electronics fields. In order to obtain insight into spin and vibronic level control of excited state lifetimes, we have initiated a study of new diimine platinum(II) dichalcogenolenes that possess charge-separated dichalcogenolene → diimine excited states. Square planar (dichalcogenolene)Pt(diimine) complexes have garnered considerable interest due to their rich photochemical properties and their bright photoluminescence behavior. We have used a combination of electronic absorption and transient spectroscopies, spectroscopic calculations, and group theoretical arguments to understand the remarkable dependence of excited state lifetimes on the nature of the heteroatom donors of the dichalcogenolene ligand, and static distortions in the acceptor ligand that lower the symmetry of the complex and destroy planarity. Our results indicate that anisotropic covalency and low-symmetry distortions control spin orbit and vibronic spin orbit coupling, and these are the origin of enhanced T1→S0 intersystem crossing in these systems. The (dithiolene)Pt(biquinoline) system possesses a T1 → S0 lifetime that is nearly two orders of magnitude less than that observed for planar (dithiolene)Pt(bipyridine). This is due to a strong static distortion driven spin-orbit coupling contribution that can be used to evaluate vibronic spin orbit coupling contributions to the T1 → S0 lifetimes in other (dichalcogenolene)Pt(diimine) complexes. New molecular frameworks that employ persistent radicals coordinated to Pt have recently been synthesized. We discuss their unique electronic structures, which have been probed by spectroscopic and computations studies, in order to understand the excited state dynamics of radical elaborated chromophores.
