Mimicking Photosystem I with a Transmembrane Light Harvester and Energy Transfer‐Induced Photoreduction in Phospholipid Bilayers

Abstract

Photosystem I (PS I) is a transmembrane protein that assembles perpendicular to the membrane, and performs light harvesting, energy transfer, and electron transfer to a final, water‐soluble electron acceptor. We present here a supramolecular model of it formed by a bicationic oligofluorene 12+ bound to the bisanionic photoredox catalyst eosin Y (EY2−) in phospholipid bilayers. According to confocal microscopy, molecular modeling, and time dependent density functional theory calculations, 12+ prefers to align perpendicularly to the lipid bilayer. In presence of EY2−, a strong complex is formed (Ka=2.1±0.1×106 m−1), which upon excitation of 12+ leads to efficient energy transfer to EY2−. Follow‐up electron transfer from the excited state of EY2− to the water‐soluble electron donor EDTA was shown via UV–Vis absorption spectroscopy. Overall, controlled self‐assembly and photochemistry within the membrane provides an unprecedented yet simple synthetic functional mimic of PS I.

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“…c) Light-absorption by a transmembrane oligoaromatic chromophore, followed energy transfer to the acceptor, eosin Y and electron transfer at the membrane interface to water. Image reproduced from ref [25]…”