Electron and energy transfer in a porphyrin–oxoporphyrinogen–fullerene triad, ZnP–OxP–C₆₀

Chahal, Mandeep K.; Gobeze, Habtom B.; Webre, Whitney A.; Karr, Paul A.; Payne, Daniel T.; Ariga, Katsuhiko; D’Souza, Francis and Hill, Jonathan P. (2020). Electron and energy transfer in a porphyrin–oxoporphyrinogen–fullerene triad, ZnP–OxP–C₆₀. Physical Chemistry Chemical Physics, 22(25) pp. 14356–14363.

DOI: https://doi.org/10.1039/d0cp02696d

Abstract

A multichromophoric triad, ZnP–OxP–C₆₀ containing porphyrin (ZnTPP hereafter ZnP), oxoporphyrinogen (OxP) and fullerene (C₆₀) has been synthesized to probe the intramolecular dynamics of its electron and energy transfer in relation to the presence of the closely linked electron deficient OxP–C₆₀ ‘special pair’, constructed as a mimic of the naturally occurring photosynthetic antenna-reaction center. The DFT optimized structure of the triad reveals the relative spatial remoteness of the ZnP entity with proximal OxP/C₆₀ entities. Free-energetics of different energy and electron transfer events were estimated using spectral, computational and electrochemical studies, according to the Rehm–Weller approach. Femtosecond transient absorption spectral studies revealed energy transfer from ¹ZnP* to OxP to yield ZnP–¹OxP*–C₆₀, and electron transfer to yield ZnP˙⁺–OxP–C₆₀˙⁻ and/or ZnP–OxP˙⁺–C₆₀˙⁻ charge seperated states. That is, the ZnP entity in the triad operates as both antenna and electron donor to generate relatively long-lived charge separated states thus mimicking the early photoevents of natural photosynthesis.

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