BODIPY(Boron-dipyrromethene) based chromophores can be used as organic-based triplet photosensitizers for various applications. As triplet photosensitizers, the formation of the triplet state is critical and understanding how to modulate the formation of the triplet state is essential to further develop BODIPY-based photosensitizers for solar energy conversion and photodynamic therapy. In our work, we have investigated the ability of halogen bonding, a directional non-covalent solvent interaction, to alter the ultrafast photophysics of 2,6-diiodo-BODIPY (BODIPY-2I) by applying ultrafast white-light pump-probe spectroscopy (WLPP). We performed solvent dependent pump-probe studies of BODIPY-2I dissolved in varying pyridine-based halogen bonding solvents. Applying a global and target analysis to WLPP spectra we find that halogen bonding facilitates the formation of the triplet state by increasing the ISC rate constant of BODIPY-2I by 36%. We interpret the results in terms of the Marcus expression for ISC and the results of TD-DFT calculations. The TD-DFT calculations indicate that halogen bonding acts to alter both the spin-orbit coupling term and the relative energetics of the singlet and triplet states.

Ultrafast spectroscopy reveals halogen bonding promotes intersystem-crossing in iodo-BODIPY chromophores

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.