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Controlling electron and energy transfer paths by selective excitation in a zinc porphyrin–BODIPY–C60 multi-modular triad

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Abstract

A multi-modular donor–acceptor triad composed of zinc porphyrin, BF2-chelated dipyrromethene (BODIPY), and C60 was newly synthesized, with the BODIPY entity at the central position. Using absorbance and emission spectral, electrochemical redox, and computational optimization results, energy level diagrams for the ZnP–BODIPY dyad and ZnP–BODIPY–C60 triad were constructed to envision the different photochemical events upon selective excitation of the BODIPY and ZnP entities. By transient absorption spectral studies covering a wide femtosecond-to-millisecond time scale, evidence for the different photochemical events and their kinetic information was secured. Efficient singlet–singlet energy transfer from 1BODIPY* to ZnP with a rate constant kENT = 1.7 × 1010 s−1 in toluene was observed in the case of the ZnP–BODIPY dyad. Interestingly, in the case of the ZnP–BODIPY–C60 triad, the selective excitation of ZnP resulted in electron transfer leading to the formation of the ZnP˙+–BODIPY–C60˙ charge-separated state. Owing to the distal separation of the radical cation and radical anion species (edge-to-edge distance of 18.7 Å), the radical ion-pair persisted for microseconds. By contrast, the selective excitation of BODIPY resulted in an ultrafast energy transfer to yield ZnP–BODIPY–1C60* as the major product. The 1C60* populated the low-lying 3C60* via intersystem crossing prior to returning to the ground state. The present study successfully demonstrates the importance of supramolecular geometry and selection of excitation wavelength in regulating the different photoprocesses.

Graphical abstract: Controlling electron and energy transfer paths by selective excitation in a zinc porphyrin–BODIPY–C60 multi-modular triad

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Publication details

The article was received on 07 Sep 2017, accepted on 13 Oct 2017 and first published on 18 Oct 2017


Article type: Paper
DOI: 10.1039/C7NR06687B
Citation: Nanoscale, 2017, Advance Article
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    Controlling electron and energy transfer paths by selective excitation in a zinc porphyrin–BODIPY–C60 multi-modular triad

    C. O. Obondi, G. N. Lim, P. Martinez, V. Swamy and F. D'Souza, Nanoscale, 2017, Advance Article , DOI: 10.1039/C7NR06687B

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