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A series of small donor-acceptor (D-A) systems based on quinoline derivatives bearing a fluorenyl motif were synthesized through Ru-catalyzed reactions. Their photophysical, electrochemical, and structural properties were investigated deeply. The photoluminescence spectra of most of the compounds were characterized by an intense band at λ ≈ 400 nm, whereas a redshifted band occurred at λ = 560 nm if the substituent of the quinoline was changed to the strongly electron-withdrawing NO2 group. Most of the synthesized compounds exhibited appealing luminescence and electrical properties, which might make them useful materials for photovoltaics. Preliminary electrical conductivity measurements of indium tin oxide/compound/Al devices showed that the current is enhanced as the applied voltage increases and, therefore, proved the semiconducting properties of the investigated compounds. Moreover, one of the synthesized compound was tested as a component of the active layer in a bulk heterojunction (BHJ) solar cell, and a power conversion efficiency (PCE) of 0.25 % was obtained. [ABSTRACT FROM AUTHOR]

New quinolines bearing a 2,2′-bithiophene motif have been prepared through Ru- and In-catalyzed reactions as well as by Suzuki cross-coupling reactions. The novel quinolines have been characterized by using EI-HRMS and NMR spectroscopy. Additionally, the molecular structures of the novel quinolines were confirmed by X-ray crystallography. The photophysical and electrochemical properties of all quinoline derivatives were investigated by using absorption and luminescence spectroscopy and cyclic voltammetry. The main intense absorption bands associated with the quinoline derivatives were located between 350 and 450 nm. Intense blue-green and orange-red fluorescence, moderate Stokes shifts, and microsecond lifetimes were observed. Quinolines containing one bithiophene moiety underwent oxidation leading to dimerization, whereas bis(bithiophenyl)-substituted quinoline underwent polymerization. All the studied quinolines showed multistep reversible reduction, with 6-nitro-4-phenylquinoline being the easiest to reduce. The study of novel quinoline derivatives indicates a strong correlation between their electrochemical and spectroscopic properties and the character of the substituent (electron-donating or electron-withdrawing) in the quinoline ring. [ABSTRACT FROM AUTHOR]