Synthesis and spectroscopic properties of new azo dyes derived from 3-ethylthio-5-cyanomethyl-4-phenyl-1,2,4-triazole

Synthesis and antimicrobial activity of aryldiazenyl/arylhydrazono pyrazoles

We report the design, synthesis, and in vitro antimicrobial evaluation of functionalized pyrazoles containing a hydrazono/diazenyl moiety. Among these newly synthesized derivatives, 4-[2-(4-chlorophenyl)hydrazono]-5-methyl-2-[2-(naphthalen-2-yloxy)acetyl]-2,4-dihydro-3 H-pyrazol-3-one is a promising antimicrobial agent against Staphylococcus aureus (minimum inhibitory concentration 0.19 μg mL−1). Structure–activity relationship studies reveal that the electronic environment on the distal phenyl ring has a considerable effect on the antimicrobial potential of the hybrid analogues. Molecular docking studies into the active site of S. aureus dihydrofolate reductase also prove the usefulness of hybridizing a pyrazole moiety with azo and hydrazo groups in the design of new antimicrobial agents.

Classifications, properties, recent synthesis and applications of azo dyes

In this work, we have presented a very detailed review of the different classification of azo dyes as a function of the number of azo groups and the appropriate functional groups. Then we pointed out some chemical properties of these dyes such as reactivity, isomerization and tautomerism and listed. In the following, we have summarized some recent syntheses of azo dyes and the mechanism of azo dye/polymer conjugation. Finally, we indicate the principle of Gewald's reaction and its application to the synthesis of new azo dyes.

Study of interaction between ionic liquids and orange G in aqueous solution with UV-vis spectroscopy and conductivity meter

The interactions between Orange G (OG) with three kinds of ionic liquid surfactants (C₁₀mimBF₄, C₁₂mimBF₄, C₁₆mimBF₄) and CTAB were studied with UV-Vis spectra and conductivity measurements. The systematic changes in UV-Vis spectra with an increase of carbon-chain length may be observed in presence of OG. They correspond to CMC of every system, respectively, and the CMCs of four systems have exhibit the decrease of CMCs compared to pure surfactant. The binding constants are calculated from the results of conductivity measurements in the order of C₁₆mimBF₄>CTAB>C₁₂mimBF₄>C₁₀mimBF₄. Furthermore, system behaviors presented significant association of complex formation and micelles formation, i.e. the change in UV-Vis spectra before and after the formation of micelles in mixed systems. In addition, Fourier-transform infrared (FT-IR) spectroscopy and ¹H NMR analysis further confirmed that the complexes are formed by hydrogen bond and van der Waal force. These findings could provide scientific guidance for extraction and separation of dyes.

Red Emitting Monoazo Disperse Dyes with Phenyl(1H-benzoimidazol-5-yl) Methanone as Inbuilt Photostabilizing Unit: Synthesis, Spectroscopic, Dyeing and DFT Studies

Synthesis of three novel phenyl(1H-benzoimidazol-5-yl)methanone based fluorescent monoazo disperse dyes and their characterization by spectroscopic methods (¹H NMR, ¹³C NMR, IR and MS) are presented. Insertion of phenyl(1H-benzoimidazol-5-yl)methanone moiety bring about induced fluorescence properties and enhanced photostability as compared to the previously reported analogues (CI Solvent Yellow 14, 4-diethylamino-2-hydroxy-1-diazobenzene and 7-(diethylamino)-4-hydroxy-3-(phenyldiazenyl)-2H-chromen-2-one). Synthesized phenyl(1H-benzoimidazol-5-yl)methanone based dyes exhibited red-shifted absorption maxima (497-516 nm), high molar extinction coefficients and are emitting in the far-red region (565-627 nm). Moreover, naphthalene-comprising dyes showed negative solvatochromism while N,N-diethylamine comprising dyes showed positive solvatochromism and are in good agreement with solvent polarity graphs and the computed energy levels of highest occupied and lowest unoccupied molecular orbitals. Synthesised dyes have better photostability (light fastness) and sublimation fastness on dyed polyester and nylon compared to reported analogues. DFT calculated energies, electrophilicity index and Frontier Molecular Orbitals (FMO's) enabled to evaluate the stabilities of azo and hydrazone forms of the dyes.