Synthesis, photophysics and electrochemical properties of 1,1′-(2,2′-bithiophene-5,5′-diyl)bis(cycloalkeno[c]pyridine) as a result of the Diels-Alder reaction of 3-(2-thienyl)-1,2,4-triazine

Two π-conjugated thienylenecycloalkeno[c]pyridine (A-D)₂ (cyclopentane, 1, and cycloheptane, 2, units when n = 1 and 3, respectively) compounds were prepared using a palladium C-C coupling reaction. The π-π∗ absorption peak of compound 1 was observed at the longer wavelength of 392 nm than that of compound 2, which was observed at 364 nm. UV-Vis data reflect the interaction between the thiophene ring (donor - D) and cycloalkeno[c]pyridine (acceptor - A) units. These compounds show photoluminescence (PL) in the range of 466-470 nm and give quantum yields, Φ, of 15%. Furthermore, intermediates 5 and 6 are characterized by their shorter absorption peaks (304 and 292 nm, respectively). The electrochemical parameters of compounds 1 and 2 were characterized using cyclic voltammetry (CV) measurements and theoretical calculations at the DFT/B3LYP/6-311++G(d,p) level.