Bodipy-squaraine triads: Preparation and study of the intramolecular energy transfer, charge separation and intersystem crossing

Year: 2017

Authors: Dong Y., Iagatti A., Foggi P., Zhao J., Mazzone G., Xu K., Ji W., Di Donato M., Russo N.

Autors Affiliation: 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; Univ Firenze, Dipartimento Chim Ugo Shiff, Via Lastruccia 3-13, I-50019 Sesto Fiorentino, Italy; Ist Nazl Ottica, Largo Enrico Fermi 6, I-50125 Florence, Italy; Univ Perugia, Dipartimento Chim, Via Elce Sotto 8, I-06123 Perugia, Italy; ICCOM CNR, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Italy; Univ Calabria, Dipartimento Chim & Tecnol Chim, I-87036 Arcavacata Di Rende, Italy.

Abstract: Two triads (BDP-SQ and Styryl-BDP-SQ) were prepared with Bodipy, styrylBodipy and Squaraine (SQ) units. SQ shows unexpected efficient intersystem crossing (ISC. phi(T) = 50%), which is attributed to S-1 -> T-1 transition. In the two triads, the Forster Resonance Energy Transfer (FRET) direction, as well as the spatial localization of the T-1 state, was judiciously tuned. The cascade photophysical properties of the triads were studied with steady-state and time -resolved optical spectroscopies, as well as with electrochemical characterization and theoretical computations. We show that triplet state was produced in triad BDP-SQ upon photoexcitation, but in Styryl-BDP-SQ the fast FRET and the charge separation (CS) processes compete with the ISC of the SQ unit, and no triplet state was formed upon photoexcitation. The singlet energy transfer kinetics were found to be 1.6 and 0.6 ps, respectively and are solvent polarity dependent. Charge transfer was confirmed with ultrafast transient absorption spectroscopy.

Journal/Review: DYES AND PIGMENTS

Volume: 147      Pages from: 560  to: 572

More Information: We thank the NSFC (21473020, 21673031, 21273028, 21421005 and 21603021), Program for Changjiang Scholars and Innovative Research Team in University [IRT_13R06], the Fundamental Research Funds for the Central Universities (DUT16TD25, DUT15ZD224, DUT2016TB12) for financial support. This project has received funding from the European Union´s Horizon 2020 research and innovation programme under grant agreement No 654148 Laserlab-Europe (Laserlab-Europe, H2020 EC-GA 654148).
KeyWords: Absorption spectroscopy; Charge transfer; Energy transfer; Photoexcitation; Solvents, Charge recombinations; Charge separations; FRET; Inter-system crossings; Triplet state, Separation, Absorption; Charge Transfer; Spectroscopy
DOI: 10.1016/j.dyepig.2017.08.028

Citations: 11
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