A simple zinc-porphyrin-NDI dyad system generates a light energy to proton potential across a lipid membrane

We report a simple donor-acceptor dyad system capable of acting as an artificial mimic of the photosynthetic apparatus by transporting electrons across a lipid bilayer resulting in the conversion of light energy to a proton potential. The active dyad described here consists of a zinc-porphyrin as a donor and NDI as an acceptor, connected through a dithiophene spacer. Incorporation of the dyad into a lipid bilayer, followed by excitation of the zinc-porphyrin, resulted in charge separation to create a reduction potential near the inner surface and an oxidation potential near the outer surface. This led to transmembrane electron transfer where quinone was converted into hydroquinone inside the vesicle by accepting protons from the HPTS dye, creating a pH gradient. This phenomenon was supported by use of a control molecule without an appropriate spacer and electrochemical and photophysical measurements further support the existence of charge separated states and formation of stable radicals.