Super Photoacids

Tolbert LM, Solntsev KM (2002) Excited-state proton transfer from constrained systems to super photoacids to superfast proton transfer. Acc Chem Res 35 19-27... 

Since the excited-state pKf of the GFP chromophore is less than zero already in the protein, then this chromophore, by analogy with the hydroxycamptothecin outlined above, also falls into the category of biological super photoacids. Isolated synthetic GFP and its derivatives do not fluoresce outside the y9-barrel at room temperature due to very effective internal conversion related to isomerization along the double bond [59-63]. Deep understanding of the photophysics of these dyes as well as synthesis of their fluorescence derivatives capable of ESPT are our immediate goals. We anticipate further studies in biological proton transfer will be facilitated by these powerful new photophysical tools. 

When the photoacid generator, triphenylsulfonium hexafluoroantimonate, is exposed to radiation, it decomposes to release the super acid, hexafluoroantimonic acid, in the resist film. While this photochemical reaction can occur at room temperature, the acid-catalyzed deprotection of the pendant r-butyl group of the resist polymer occurs at reasonable rates only at elevated temperature. It is therefore necessary to heat the resist film to an appropriate temperature (postexposure bake) to provide the energy that is required for the acid-catalyzed deprotection of the r-butyl group of the ester, which in turn, affords the base-soluble norbomene carboxylic acid unit isobutylene volatilizes. The extent of deprotection at constant temperature is... 

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