Triplet Excited State of BODIPY Accessed by Charge Recombination and Its Application in Triplet-Triplet Annihilation Upconversion

Year: 2017

Authors: Chen K., Yang W., Wang Z., Iagatti A., Bussotti L., Foggi P., Ji W., Zhao J., Di Donato M.

Autors Affiliation: Dalian Univ Technol, State Key Lab Fine Chem, Sch Chem Engn, E-208 West Campus,2 Ling Gong Rd, Dalian 116024, Peoples R China; LENS, Via N Carrara 1, I-50019 Sesto Fiorentino, Italy; Ist Nazl Ott Largo Enr, INO, Fermi 6, I-50125 Florence, Italy; Univ Perugia, Dipartimento Chim, Via Elce Sotto 8, I-06123 Perugia, Italy; Dalian Univ Technol, Sch Chem, E-208 West Campus,2 Ling Gong Rd, Dalian 116024, Peoples R China.

Abstract: The triplet excited state properties of two BODIPY phenothiazine dyads (BDP-1 and BDP-2) with different lengths of linker and orientations of the components were studied. The triplet state formation of BODIPY chromophore was achieved via photoinduced electron transfer (PET) and charge recombination (CR). BDP-1 has a longer linker between the phenothiazine and the BODIPY chromophore than BDP-2. Moreover, the two chromophores in BDP-2 assume a more orthogonal geometry both at the ground and in the first excited state (87 degrees) than that of BDP-1 (34-40 degrees). The fluorescence of the BODIPY moiety was significantly quenched in the dyads. The charge separation (CS) and CR dynamics of the dyads were studied with femtosecond transient absorption spectroscopy (k(CS) = 2.2 X 10(11) s(-1) and 2 X 10(12) s(-1) for BDP-1 and BDP-2, respectively; k(CR) = 4.5 X 10(10) and 1.5 X 10(11) s(-1) for BDP-1 and BDP-2, respectively; in acetonitrile). Formation of the triplet excited state of the BODIPY moiety was observed for both dyads upon photoexcitation, and the triplet state quantum yield depends on both the linker length and the orientation of the chromophores. Triplet state quantum yields are 13.4 and 97.5% and lifetimes are 13 and 116 mu s for BDP-1 and BDP-2, respectively. The spin-orbit charge transfer (SO-CT) mechanism is proposed to be responsible for the efficient triplet state formation. The dyads were used for triplet-triplet annihilation (TTA) upconversion, showing an upconversion quantum yield up to 3.2%.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY A

Volume: 121 (40)      Pages from: 7550  to: 7564

More Information: We thank the NSFC (21473020, 21673031, 21273028, 21421005, and 21603021), Program for Changjiang Scholars and Innovative Research Team in University [IRT_13R06], and the Fundamental Research Funds for the Central Universities (DUT16TD25, DUT15ZD224, DUT2016TB12) for financial support.
KeyWords: Absorption spectroscopy; Charge transfer; Chromophores; Insecticides; Quantum theory; Quantum yield, Charge recombinations; Charge separations; Excited-state properties; Femtosecond transient absorption spectroscopy; First excited state; Orthogonal geometry; Photo-induced electron transfer; Triplet-triplet annihilation, Excited states
DOI: 10.1021/acs.jpca.7b07623

Citations: 96
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