Abstract

AbstractOne or multiple chlorophyll a molecules are employed in the reaction center of photosystem II′s main electron donor (defined as P680). We have a poor understanding of how the reaction center facilitates water oxidation in photosystem II and the roles that mono‐ and/or multimeric chlorophyll groups play when P680 oxidizes a neighboring tyrosine in order to drive water oxidation at the oxygen evolving complex. We have prepared a dimeric MgII‐porphyrin complex [Mg2(BTPP)] (1, H4‐BTPP=1,2‐bis‐(10,15,20‐triphenylporphyrin‐5‐yl)‐benzene) as a structural and functional mimic of the dimeric core of P680. 1 was oxidized by one‐electron to the corresponding π‐cation radical complex 2. The radical cation was characterized by UV/Vis‐NIR, FT‐IR, and EPR spectroscopic techniques. 2 was shown to be reactive towards phenols to give the corresponding phenoxyl radicals, mimicking the reactivity of the P680 cation radical which oxidizes tyrosine to tyrosyl radical. Critically, the dimeric π‐cation radical showed markedly higher rates of proton coupled electron transfer oxidation (PCET) of phenols when compared to its monomeric counterpart [Mg(TPP)] (TPP=5,10,15,20‐tetraphenylporphyrin). Our findings demonstrate that MgII‐porphyrin complexes are reliable mimics of photosynthetic PCET processes and suggest that photosynthetic reaction centers with multiple π‐conjugated complexes likely lower the barrier to PCET oxidation by π‐cation radical species.

Talk to us

Join us for a 30 min session where you can share your feedback and ask us any queries you have

Schedule a call

Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.