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

Phenylazoindole dyes 3: Determination of azo-hydrazone tautomers of new phenylazoindole dyes in solution and solid state

“…However, the stability of the azo tautomer slightly increases from DMSO to chloroform with decreasing dielectric constant. The energy analyses for stabilities of the dyes show that the azo form is more stable than the hydrazone form both in gas phase and solution [17]. In our continuation study, the electronic spectra of the compounds in azo and hydrazone forms were also obtained in the framework of TD-DFT calculations with B3LYP using 6-311+g(d,p) basis set to support the assignment of absorption bands for azo and hydrazone forms.…”

“…Among the different methods, UV-vis and NMR spectroscopy are still the best methods for qualitative studies of tautomeric behavior in solutions. Also, the useful system for determination of the azo-hydrazone tautomerism is to use model compounds [16][17][18][19][20][21][22]36].…”

“…In our earlier studies, we have synthesized and determined the tautomeric behaviors of a number of aryl/heteroarylazo indole dyes in solution and solid state [16][17][18][19][20][21][22] Fig. 1.…”

Azobenzene as Antimicrobial Molecules

“…Organic molecules used in combination with azo moiety include heterocycles such as pyrimidines [ 52 ], indoles [ 53 ], pyrazoles [ 54 ], triazoles, benzothiazoles, and thiazoles, which have shown good antimicrobial activity. In recent years, interest in azo dyes has increased more and more due to the possibility of synthesizing derivatives of antibiotic drugs by binding with azobenzene molecules, which are more potent than originator drugs.…”

Synthesis, Characterization, Absorption and Fastness Properties of Novel Monoazo Dyes Derived from 1-Phenyl-3-amino-4-(2-thiazolilazo)pyrazol-5-one

“…The synthesized new dyes may exist in five possible tautomeric forms, i.e., keto-azo (T 1 and T 5 ), keto-hydrazo (T 2 and T 4 ) and enol-azo (T 3 ). According to the calculation results in the literature, 17,[35][36][37][38][39][40] the most stable tautomeric form is keto-hydrazo form (T 2 ) for hetarylazopyrazolone dyes. This conclusion may occur from the intramolecular O−H bond.…”