Ewa Olender

Synthesis, photophysics and electrochemistry of novel, nitrogen-containing heterocyclic derivatives

A series of new π-conjugated donor (thienyl – T) and acceptor (A) oligomers were prepared by Stille coupling reaction. The T–A oligomers consisting of thiophene/bithiophene as donors and 1,2,4-triazine as an acceptor were prepared to investigate their photophysical and electrochemical properties. These compounds were spectroscopically confirmed to be highly conjugated. These UV-vis data show that the number and position of the thiophene considerably affect the width of the HOMO–LUMO gap and the rigidity of the conjugated system. Compounds A2TA, A3TA, A4TA show photoluminescence in a range 466–543 nm.

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.

Ethyl 2-(3-methyl-5-sulfanyl­idene-4,5-dihydro-1H-1,2,4-triazol-4-yl)acetate

The title compound, C7H11N3O2S, exists in the 5-thioxo tautomeric form. The 1,2,4-triazoline ring is essentially planar, with a maximum deviation of 0.010 (2) Å for the substituted N atom. The ethyl acetate substituent is almost planar, with a maximum deviation of 0.061 (4) Å for the methylene C atom of the ethoxy group. The angle between the mean plane of this substituent and the mean plane of the 1,2,4-triazoline ring is 89.74 (8)°. In the crystal, molecules are linked by a combination of N—H⋯S, C—H⋯N and C—H⋯O hydrogen bonds into chains parallel to [100].

A convenient synthesis of 5,5'-bi-1,2,4-triazines via direct S-arylation and its application in the synthesis of 2,2'-bipyridines

Abstract Nucleophilic displacement of chlorides in 3,3′-dichloro-5,5′-bi-1,2,4-triazine with benzenethiolate or 2-pyridinethiolate anion afforded the corresponding symmetrical disulfide of 5,5′-bi-1,2,4-triazine in high yields. These products were transformed into 6,6′-bis(phenylthio)-2,2′-bipyridines and 6,6′-bis(2-pyridylthio)-2,2′-bipyridines by using Diels-Alder reactions. All compounds were fully characterized by spectroscopic methods and the X-ray diffraction analysis.