Photobehavior and Nonlinear Optical Properties of Push-Pull, Symmetrical, and Highly Fluorescent Benzothiadiazole Derivatives

Year: 2016

Authors: Ricci F., Elisei F., Foggi P., Marrocchi A., Spalletti A., Carlotti B.

Autors Affiliation: Univ Perugia, Dept Chem Biol & Biotechnol, Via Elce Sotto 8, I-06123 Perugia, Italy; Univ Perugia, CEMIN, Via Elce Sotto 8, I-06123 Perugia, Italy; LENS, Via Nello Carrara 1, I-50019 Florence, Italy; INO CNR, Largo Fermi 6, I-50125 Florence, Italy.

Abstract: Three quadrupolar D-pi-A-pi-D compounds, bearing alkoxy phenyls as mild electron donors and a benzothiadiazole (A), two benzothiadiazoles (B), or a benzothiadiazole linked to two thiophenes (C) as the acceptor units, are collectively the object of this study. They proved to be efficient yellow/orange/red fluorophores, respectively, with fluorescence being their preferred deactivation pathway. These systems exhibited positive fluorosolvatochromism and a noticeable decrease of the fluorescence quantum yield in the most polar solvent (with the quenching following the trend B > A > C). These findings point to an intramolecular charge transfer (ICT) nature of the emitting state, whose photoinduced dynamics was investigated by femtosecond-resolved transient absorption and fluorescence upconversion. Remarkable values of hyperpolarizability were estimated by the solvatochromic method. The significant two-photon absorption cross sections measured for A-C (whose trend nicely parallels that of ICT efficiency), coupled. with the intense emission, make them promising for applications as environment-sensitive probes in two-photon excited fluorescence imaging.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY C

Volume: 120 (41)      Pages from: 23726  to: 23739

More Information: We acknowledge support from the Italian Ministero per l’Universita e la Ricerca Scientifica e Tecnologica, MIUR (Rome, Italy) under the FIRB Futuro in Ricerca 2013, no. RBFR13PSB6. Dr. Rebecca Flamini is kindly acknowledged for previous experimental work and useful discussions that inspired this work.
KeyWords: Charge transfer; Fluorescence; Fluorophores; Nonlinear optics; Optical properties; Photons; Two photon processes, Benzothiadiazole derivatives; Fluorescence quantum yield; Fluorescence upconversion; Intramolecular charge transfers; Non-linear optical properties; Solvatochromic methods; Two-photon absorption cross section; Two-photon excited fluorescence, C (programming language)
DOI: 10.1021/acs.jpcc.6b07290

Citations: 60
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