Synthesis, characterization, spectroscopy and biological activity of 4-((3-formyl-4-hydroxyphenyl)azo)-1-alkylpyridinium salts

Abstract

The reaction of 2-hydroxy-5-(pyridine-4-yldiazenyl)benzaldehyde with n-alkyl bromides generated five novel azo pyridinium salts in good to excellent yields. The 1 H and 13 C NMR and UV-Vis absorption spectra indicated several tautomers for the new compounds. The NMR, UV-Vis absorption spectra and quantum chemical calculations show that the azo pyridinium salts have a new resonant structure compared to the corresponding azo precursor. Antibacterial activity was studied by disc diffusion and MIC methods. Diphenylpicrylhydrazyl (DPPH) assay was used to determine the antioxidant properties. The effects of carbon chain length on antimicrobial activity were also investigated. The results showed that existence of alkyl groups is crucial for the antibacterial properties. The new compound with decyl group displayed the best antibacterial activity. prepared and purified according to the method reported in the literature. 19 Melting points were measured on an Electrothermal 9200 apparatus. Mass spectra were recorded on an Agilent MS Model 5973. FT-IR spectra were recorded on a Shimadzu 8400S spectrometer using KBr disc. The electronic absorption spectra were recorded with a Shimadzu 1650 spectrophotometer. 1 H and 13 C NMR spectra were recorded in DMSO-d 6 as the solvent on the Bruker DRX-300 MHz and 400 MHz Advance spectrometers.

Preparation of reactive amphoteric polyurethane with multialdehyde groups and its use as a retanning agent for chrome‐free tanned leather

“…We speculate that this might have been due to the implantation of DDBA into the AAPU molecule, where the conjugation effect existed between the carbonyl (CO) and benzene ring; this prompted the transition of n electrons in CO to the π* orbit on the benzene ring. Therefore, a UV absorption peak was generated at 262 nm, and this result was similar to those reported in the literature …”

Synthesis, characterization and in vitro biological screening of 4-hydroxy naphthalen-1-yl, naphtho[1,2-b]furan, benzo[h]chromene and 5,6-dihydropyridazine derivatives containing sulfonamide moiety

“…NMR Spectra were recorded on a Bruker spectrophotometer (Bruker, Karlsruhe, Germany). 1 H spectrum was run at 400 MHz in deuterated dimethylsulfoxide (DMSO-d6). Chemical shifts are expresses in values (ppm) relative to TMS as an internal standard.…”

“…The infrared spectra of compounds 3a-e showed the presence of absorption band at 3357-3448 cm -1 which is characteristic of the hydroxyl group beside two absorptions bands for azo and sulfone groups. The representative 1 HNMR spectrum of compound 3a (DMSO-d6) shown 7.1, 7.75, 8.35, 8.80 (4d, 4H, naphtho-H), 7.47, 7.58 (2m, 2H, naphtho-H), 7.94, 8.24 (2d, 4H, AB-system), 8.10 (s, 2H, NH2 exchangeable with D2O), 12.36 (br, 1H, OH exchangeable with D2O). The molecular ion peak of compound 3c was observed at m/z 410 (42.83%) corresponding to the molecular formula C19H14N4O3S2, and the base peak was found in the spectrum at m/z 65.…”

“…Substituted azobenzene have attracted considerable attention based on their various physical and chemical properties, such as bright colors, good stability, low flammability, and rapid, reversible photo-isomerization [1][2][3][4] . Aromatic azo compounds are widely used in the chemical industry as dyes, pigments 5,6 , food additives 7, indicators 3 , radical reaction initiators 8 and therapeutic agents 9,10 .…”