A Revisit to the Orthogonal Bodipy Dimers: Experimental Evidence for the Symmetry Breaking Charge Transfer-Induced Intersystem Crossing

Year: 2018

Authors: Liu Y., Zhao JZ., Iagatti A., Bussotti L., Foggi P., Castellucci E., Di Donato M., Han KL.

Autors Affiliation: Chinese Acad Sci, Dalian Inst Chem Phys, State Key Lab Mol React Dynam, 457 Zhongshan Rd, Dalian 116023, Peoples R China; Univ Chinese Acad Sci, Beijing 100049, Peoples R China; Dalian Univ Technol, Sch Chem Engn, State Key Lab Fine Chem, E-208 West Campus,2 Ling Gong Rd, Dalian 116024, Peoples R China; LENS European Lab Nonlinear Spect, Via N Carrara 1, I-50019 Sesto Fiorentino, Italy; INO, Largo Enrico Fermi 6, I-50125 Florence, Italy; Univ Perugia, Dipartimento Chim, Via Elce Sotto 8, I-06123 Perugia, Italy.

Abstract: A series of Bodipy dimers with orthogonal conformation were prepared. The photophysical properties were studied with steady-state and time-resolved transient spectroscopies. We found the triplet-state quantum yield is highly dependent on the solvent polarity in the orthogonally linked symmetric Bodipy dimers, and the intersystem crossing (ISC) is efficient in solvents with moderate polarity. The photoinduced symmetry-breaking charge transfer (SBCT) in polar solvents was confirmed by femtosecond transient absorption spectroscopy, with the charge separation (CS) kinetics on the order of a few picoseconds and the charge recombination (CR) process occurring on the nanosecond time scale in dichloromethane. These observations are supported by the calculation of the charge separated state (CSS) energy levels, which are high in nonpolar solvents, and lower in polar solvents, thus the CR-induced ISC has the largest driven force in solvents with moderate polarity. These results clarify the mechanism of SOCT-ISC in the orthogonally symmetric Bodipy dimers. The acquired information, relating molecular structure and ISC property, will be useful for devising new strategies to induce ISC in heavy atom-free organic chromophores.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY C

Volume: 122 (5)      Pages from: 2502  to: 2511

More Information: We thank the NSFC (21473020, 21673031, 21273028, 21421005, 21761142005, and 21603021), the Fundamental Research Funds for the Central Universities (DUT16TD25, DUT15ZD224, DUT2016TB12) for financial support.
KeyWords: Singlet Oxygen Generation; Excited Triplet-state; Photoinduced Electron-transfer; Halogen-free Photosensitizers; Visible-light; Photodynamic Therapy; Energy-transfer; Up-conversion; Systems; Enhancement
DOI: 10.1021/acs.jpcc.7b10213

Citations: 87
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