A Panchromatic Supramolecular Fullerene-Based Donor–Acceptor Assembly Derived from a Peripherally Substituted Bodipy–Zinc Phthalocyanine Dyad

Authors


  • Bodipy=4,4-difluoro-4-bora-3a,4a-diaza-s-indacene.

Abstract

A panchromatic 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene –zinc phthalocyanine conjugate (Bodipy–ZnPc) 1 was synthesized starting from phthalocyanine aldehyde 4, via dipyrromethane 3 and dipyrromethene 2. Conjugate 1 represents the first example in which a Bodipy unit is tethered to the peripheral position of a phthalocyanine core. Electrochemical and optical measurements provided evidence for strong electronic interactions between the Bodipy and ZnPc constituents in the ground state of 1. When conjugate 1 is subjected to photoexcitation in the spectral region corresponding to the Bodipy absorption, the strong fluorescence characteristic of the latter subunit is effectively quenched (i.e., ≥97 %). Excitation spectral analysis confirmed that the photoexcited Bodipy and the tethered ZnPc subunits interact and that intraconjugate singlet energy transfer occurs with an efficiency of ca. 25 %. Treatment of conjugate 1 with N-pyridylfulleropyrrolidine (8), an electron-acceptor system containing a nitrogen ligand, gives rise to the novel electron donor–acceptor hybrid 18 through ligation to the ZnPc center. Irradiation of the resulting supramolecular ensemble within the visible range leads to a charge-separated Bodipy–ZnPc.+–C60.− radical-ion-pair state, through a sequence of excited-state and charge transfers, characterized by a remarkably long lifetime of 39.9 ns in toluene.

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