Ergin Yalçın

Synthesis, spectroscopic properties, and antimicrobial activity of some new 5-phenylazo-6-aminouracil-vanadyl complexes

Six complexes, [VO(L1-H)2] · 5H2O (1), [VO(OH)(L2,3−H)(H2O)] · H2O (2,3), [VO(OH)(L4,5−H)(H2O)] · H2O (4,5), [VO(OH)(L6−H)(H2O)] · H2O (6), were prepared by reacting different derivatives of 5-phenylazo-6-aminouracil ligands with VOSO4 · 5H2O. The infrared and 1H NMR spectra of the complexes have been assigned. Thermogravimetric analyses (TG, DTG) were also carried out. The data agree quite well with the proposed structures and show that the complexes were finally decomposed to the corresponding divanadium pentoxide. The ligands and their vanadyl complexes were screened for antimicrobial activities by the agar-well diffusion technique using DMSO as solvent. The minimum inhibitory concentration (MIC) values for 1–4 and 6 were calculated at 30°C for 24–48 h. The activity data show that the complexes are more potent antimicrobials than the parent ligands.

Phenylazoindole dyes – Part I: The syntheses, characterizations, crystal structures, quantum chemical calculations and antimicrobial properties

In this study, the synthesis of four new phenylazo indole dyes (dye 1-4) were carried out by diazotization of 4-aminoacetophenone and coupling with various 2- and 1,2-disubstituted indole derivatives. The dyes were characterized by UV-vis, FT-IR, (1)H NMR, HRMS and X-ray single crystal diffraction methods. Azo-hydrazone tautomeric bahavior of the dyes in different solvents (DMSO, methanol, acetic acid and chloroform) was investigated by using (1)H NMR and UV-vis results. The experimental results were compared with the corresponding calculated values. The results of experimental data and theoretical calculations showed that the azo tautomer is more stable than hydrazone tautomer. In addition to this, the antimicrobial activity of the dyes was also evaluated.

Efficient one-pot three-component method for the synthesis of highly fluorescent coumarin-containing 3,5-disubstituted-2,6-dicyanoaniline derivatives under microwave irradiation

ABSTRACT A simple and concise approach to the synthesis of coumarin-containing highly fluorescent asymmetric/symmetric 3,5-diaryl/heteroaryl-2,6-dicyanoaniline derivatives are reported. The compounds were synthesized through base catalyzed three-component one-pot synthesis reaction of 2-(1-(7-(diethylamino)-2-oxo-2H-chromen-3-yl)ethylidene)malononitrile, aliphatic, aromatic/heteroaromatic aldehydes, and malononitrile in solvent-free reaction medium, catalyzed by piperidine under microwave irradiation method. The reaction gave the novel, highly fluorescent coumarin-containing 3,5-disubstituted-2,6-dicyanoaniline derivatives in good yields at 300 W, 80 °C in 2 min. This method provides several advantages; such as shorter reaction time, environmental friendliness, simple workup procedure, lower energy consumption and, generally, good yields with high purity. In addition, the synthesized compounds are fluorescently active dyes even in day light, except for compounds including nitro substituent, and show maximum absorption wavelengths (λabs.max) in the visible region in DMSO at room temperature. Thermal properties of all the synthesized compounds were also evaluated with thermal gravimetric analysis for usability as optic dye. Optical and thermal screening studies of the compounds showed that the dyes have excellent photophysical and thermal stability properties. GRAPHICAL ABSTRACT

Investigation of binding properties of dicationic styrylimidazo[1,2-a]pyridinium dyes to human serum albumin by spectroscopic techniques

The binding interaction between two dicationic styrylimidazo[1,2-a]pyridinium dyes and human serum albumin (HSA) was investigated at physiological conditions using fluorescence, UV-vis absorption, and circular dichroism (CD) spectroscopies. Analysis of the fluorescence titration data at different temperatures suggested that the fluorescence quenching mechanism of HSA by these dyes was static. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that hydrogen bonding and van der Waals forces played a major role in the formation of the dye-HSA complex. Binding distances (r) between dyes and HSA were calculated according to Försters non-radiative energy transfer theory. Studies of conformational changes of HSA using CD measurements indicate that the α-helical content of the protein decreased upon binding of the dyes. Copyright

5,6-Diphenyl-pyrazine-2,3-dicarbonitrile.

In the title compound, C18H10N4, the pyrazine ring is oriented at dihedral angles of 48.08 (7) and 44.80 (7)° with respect to the phenyl rings, while the dihedral angle between the phenyl rings is 49.47 (7)°. In the crystal structure, weak π–π contacts between pyrazine and phenyl rings [centroid–centroid distance = 3.813 (1) Å] may stabilize the structure.