Efficient Photoinduced Charge Separation in a BODIPY-C-60 Dyad

Year: 2016

Authors: Iagatti A., Cupellini L., Biagiotti G., Caprasecca S., Fedeli S., Lapini A., Ussano E., Cicchi S., Foggi P., Marcaccio M., Mennucci B., Di Donato M.

Autors Affiliation: LENS European Lab Nonlinear Spectroscopy, Via N Carrara 1, I-50019 Sesto Fiorentino, Italy; INO CNR Ist Nazl Ottica, Largo Fermi 6, I-50125 Florence, Italy; Univ Pisa, Dipartimento Chim & Chim Ind, Via G Moruzzi 13, I-56124 Pisa, Italy; Univ Firenze, Dipartimento Chim Ugo Schiff, Via Lastruccia 13, I-50019 Sesto Fiorentino, Italy; Univ Bologna, Dipartimento Chim G Ciamician, Via Selmi 2, I-40126 Bologna, Italy; Univ Perugia, Dipartimento Chim, Via Elce Sotto 8, I-06100 Perugia, Italy.

Abstract: A donor acceptor dyad composed of a BF2-chelated dipyrromethene (BODIPY) and a C-60 fullerene has been newly synthesized and characterized. The two moieties are linked by direct addition of an azido substituted BODIPY on the C-60, producing an imino fullerene BODIPY adduct. The photoinduced charge transfer process in this system was studied by ultrafast transient absorption spectroscopy. Electron transfer toward the fullerene was found to occur selectively exciting both the BODIPY chromophore at 475 nm and the C-60 unit at 266 nm on a time scale of a few picoseconds, but the dynamics of charge separation was different in the two cases. Eletrochemical studies provided information on the redox potentials of the involved species and spectroelectrochemical measurements allowed to unambiguously assign the absorption band of the oxidized BODIPY moiety, which helped in the interpretation of the transient absorption spectra. The experimental studies were complemented by a theoretical analysis based on DFT computations of the excited state energies of the two components and their electronic couplings, which allowed identification of the charge transfer mechanism and rationalization of the different kinetic behavior observed by changing the excitation conditions.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY C

Volume: 120 (30)      Pages from: 16526  to: 16536

More Information: The authors gratefully acknowledge support from the Italian Ministero dell’Istruzione, Universita e Ricerca-MIUR program FIRB Futuro in Ricerca 2010 Grant RBFR10Y5VW to M.D.D. and program FIRB NANOSOLAR and Program FIRB Approcci nanotecnologici per la teragnostica dei tumori Grant RBAP11ETKA_002 to S. Cicchi. L.C., S. Caprasecca, and B.M. acknowledge the European Research Council (ERC) for financial support in the framework of the Starting Grant (Enlight-277755). M.D.D. wishes to acknowledge the contribution of Ente Cassa di Risparmio di Firenze. Laserlab Europe Contract No. 654148 and University of Bologna are also gratefully acknowledged.
KeyWords: Absorption spectroscopy; Charge transfer; Chromophores; Electron transport properties; Fullerenes; Redox reactions; Spectroelectrochemistry, Charge transfer mechanisms; Excitation conditions; Excited-state energy; Photoinduced charge separation; Photoinduced charge transfer; Spectroelectrochemical measurements; Transient absorption spectra; Ultrafast transient absorption spectroscopy, Excited states
DOI: 10.1021/acs.jpcc.6b05738

Citations: 26
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