Solvent- and time-dependent fluorescence of photoacids based on pyranine

TL;DRAbstract

The process of excited-state proton transfer (ESPT) is frequently found in aromatic alcohols. Upon electronic excitation, the acidity of these molecules increases by 5-10 orders of magnitude. While being in the excited state, the proton can be transferred to a suitable acceptor unit due to the high photoacidity. In this thesis, the ESPT behavior of five new photoacids in different solvents as proton acceptor is investigated. The new molecules are based on the well-known pyranine photoacid, with electronic transitions in the visible part of the electromagnetic spectrum. Steady-state and time-resolved spectroscopy is used to characterize the new molecules and prove them as “super”-photoacids, which are capable of ESPT in organic solvents. The combination of steady-state measurements with a solvatochromic analysis showed that it is an intramolecular charge transfer on the photoacid side, which correlates best with the photoacidity of the molecule. The proton transfer rate constants could

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