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Solvent Tuning Excited State Structural Dynamics in a Novel Bianthryl.

Palas RoyFaisal Al-KahtaniAndrew N CammidgeStephen R Meech
Published in: The journal of physical chemistry letters (2023)
Symmetry breaking charge separation (SBCS) is central to photochemical energy conversion. The widely studied 9,9-bianthryl (9,9'BA) is the prototype, but the role of bianthryl structure is hardly investigated. Here we investigate excited state structural dynamics in a bianthryl of reduced symmetry, 1,9-bianthryl (1,9'BA), through ultrafast electronic and vibrational spectroscopy. Resonance selective Raman in polar solvents reveals a Franck-Condon state mode that disappears concomitant with the rise of ring breathing modes of radical species. Solvent-dependent dynamics show that CS is driven by solvent orientational motion, as in 9,9'BA. In nonpolar solvents the excited state undergoes multistep structural relaxation, including subpicosecond Franck-Condon state decay and biexponential diffusion-controlled structural evolution to a distorted slightly polar state. These data suggest two possible routes to SBCS; the established solvent driven pathway in rapidly relaxing polar solvents and, in slowly relaxing media, initial intramolecular reorganization to a polar structure which drives solvent orientational relaxation.
Keyphrases
  • ionic liquid
  • energy transfer
  • single molecule
  • solar cells
  • magnetic resonance imaging
  • electronic health record
  • raman spectroscopy
  • density functional theory
  • deep learning
  • electron transfer