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

Year: 2018

Authors: Liu Y., Zhao J., Iagatti A., Bussotti L., Foggi P., Castellucci E., Di Donato M., Han K.-L.

Autors Affiliation: State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, 457 Zhongshan Road, Dalian, 116023, China; University of Chinese Academy of Sciences, Beijing, 100049, China; State Key Laboratory of Fine Chemicals, Dalian University of Technology, 2 Ling Gong Road, Dalian, 116024, China; LENS (European Laboratory for Non-Linear Spectroscopy), via N. Carrara, Sesto Fiorentino, 50019, Italy; Istituto Nazionale di Ottica Largo Enrico Fermi, Florence, I-50125, Italy; Dipartimento di Chimica, Universitá di Perugia, Via Elce di Sotto 8, Perugia, 06123, 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.


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: Absorption spectroscopy; Charge transfer; Chromophores; Dichloromethane; Dimers; Quantum theory, Charge recombinations; Charge-separated state; Experimental evidence; Femtosecond transient absorption spectroscopy; Inter-system crossings; Nanosecond time scale; Photophysical properties; Transient spectroscopy, Solvents
DOI: 10.1021/acs.jpcc.7b10213

Citations: 61
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