Molecular orbitals provide a natural language to interpret chemistry in the context of wave function. Especially, the information of multi-electronic wave functions of molecules and solids is condensed to a set of one-electron orbitals. Since the vibronic interaction involves only one-electron operator, molecular orbitals are the best tools to study this interaction and its consequent effects. In this presentation, I will talk about our recent works on vibronic interactionn: (1) deriving Hamiltonian formalism for Jahn-Teller and pseudo-Jahn-Teller problems; (2) designing singlet fission chromophores; (3) investigating singlet fission mechanism; (4) simulating photoelectron spectrum. All these models are constructed based on molecular orbitals. For instance, shown in the figure are the E3'' unoccupied orbitals and the e1' normal modes of the cycloheptatrienyl cation, and the fitted parameters for the E3'' × e1' Jahn-Teller problem. They are in perfect agreement with the derived expansion formula. For designing singlet fission chromophores, molecular orbitals help us identify molecules with clear diradical character, which are good candidates for singlet fission. For studying singlet fission mechanism, we fine tune the frontier orbitals of chromophore units and linkers to enhance fission mechanism. For the simulation of the photo-detachment spectrum, the frontier molecular orbitals of the anion explain the pseudo-Jahn-Teller nature of the spectrum.

Our vibronic coupling studies based on molecular orbitals: Formalism, spectrum, and materials

ACS Fall 2021

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