title: Benzimidazolylquinoxalines: novel fluorophores with tuneable sensitivity to solvent effects.
abstract: We report on the photophysical properties, conjugation, conformational behavior, intra- and intermolecular hydrogen bonds (HBs) of a series of novel fluorophores, consisting of 3-arylquinoxaline and benzimidazole moieties linked by a single CC bond. Computations employing density functional theory (DFT) reveal that conjugation between these moieties stabilizes syn-conformers with two HB centers located on the same side of the molecule. Anti-conformers form stronger intermolecular HBs with DMSO and DMF than syn-conformers, and this influences the energy gap between syn- and anti-forms, especially upon excitation of the molecules to the S1state. Substituents introduced in various positions of the molecules modify their conformational behavior, and mutual disposition of excited singlet states relative to the ground states. Various substitution patterns produce very different effects on relative quantum yield of luminescence: from a moderate increase in polar DMSO and DMF relative to 1,2-dichloroethane solutions to complete quenching of emission which is observable in polar media. The observed behavior is understood with the aid of DFT and time-dependent DFT calculations. The tuneability of the spectroscopic range of the luminescence and especially of its sensitivity to environmental effects allows rational design of the novel fluorophores of this family for various applications.
authors.affiliation: A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, Arbuzov str. 8, 420088 Kazan, Russia. katsyuba@iopc.ru skatsyuba@yahoo.com.
authors.forename: Timur I
authors.initials: TI
authors.lastname: Burganov
authors.affiliation: A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, Arbuzov str. 8, 420088 Kazan, Russia. katsyuba@iopc.ru skatsyuba@yahoo.com.
authors.forename: Nataliya A
authors.initials: NA
authors.lastname: Zhukova
authors.affiliation: A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, Arbuzov str. 8, 420088 Kazan, Russia. katsyuba@iopc.ru skatsyuba@yahoo.com.
authors.forename: Vakhid A
authors.initials: VA
authors.lastname: Mamedov
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie der Universität Bonn, Beringstr. 4, 53115 Bonn, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Bannwarth
authors.affiliation: Mulliken Center for Theoretical Chemistry, Institut für Physikalische und Theoretische Chemie der Universität Bonn, Beringstr. 4, 53115 Bonn, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Grimme
authors.affiliation: A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Centre of the Russian Academy of Sciences, Arbuzov str. 8, 420088 Kazan, Russia. katsyuba@iopc.ru skatsyuba@yahoo.com.
authors.forename: Sergey A
authors.identifier: http://orcid.org/0000-0001-9196-9308
authors.initials: SA
authors.lastname: Katsyuba