Effect of Solvent Polarizability on the Keto/Enol Equilibrium of Selected Bioactive Molecules from the 1,3,4-Thiadiazole Group with a 2,4-Hydroxyphenyl Function

Abstract

Three novel 1,3,4-tiadiazole-derived compounds with biological-activity, i.e., 4-(5-(methylamino)-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (MDFT), 4-(5-(phenylamino)-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (PhATB), and 4-(5-(4-chlorophenylamino)-1,3,4-thiadiazol-2-yl)benzene-1,3-diol (4-CIPhATB) were characterized with the use of several spectroscopic methods. Detailed UV-vis studies revealed keto/enol tautomerism of the examined compounds. The absorption spectra recorded in nonpolar solvents exhibited bands that were characteristic of keto tautomers, while in polar solvents the enol form is predominant. A number of spectra revealed the presence of both tautomeric forms in the solution. The keto/enol equilibria observed were both solvent- and temperature-dependent. The keto/enol equilibrium was also observed using FTIR spectroscopy. A detailed analysis of the spectroscopic data leads to a conclusion that the solvent-induced tautomerism of the selected compounds from the 1,3,4-thiadiazole group does not depend on the electric dipole moment of the solvent but more likely on its average electric polarizability. Additionally, a clear effect of the substituent present in the molecule on the tautomeric equilibrium in the selected 1,3,4-thiadiazole analogues was noted.

Characterization of membrane processed honey and the effect of ultrafiltration with diafiltration on subsequent spray drying

“…It is a rapid, reagent‐free, and cheap method of quantifying various foods and their components, i.e. : juice (Jha & Gunasekaran, ), oils, olive oil, and olive pulp (Kachel‐Jakubowska, Matwijczuk, & Gagoś, ; Matwijczuk et al, ; Yang et al, ), essential oils (Sousa et al, ), and honey saccharides (Anjos et al, ; Gok et al, ; Lichtenberg‐Kraag et al, ).…”

1,3,4-Thiadiazol derivative functionalized-Fe3O4@SiO2 nanocomposites as a fluorescent probe for detection of Hg2+ in water samples

“…The sensitivity of the probe was calculated by titration tests and it was shown that the limit of detection is 48.7 nm and the uorescence intensity diagram against Hg 2+ concentration showed a good linear relationship in the range of 0.1-0.5 mM. Theoretical calculations showed that the binding energies of S 37 , N 28 , and N 31 bonds with Hg 2+ ion has an order of S 37 > N 28 > N 31 . The presence of various active sites for coordination to mercury atoms makes this detector potential adsorbent for removing heavy metal atoms with high capacity.…”

“…has made it an attractive compound for biologists and chemists. The special structure of thiadiazole class of components enables keto/enol tautomerism which is the origin of uidity of biological membranes, 30,31 crystal polymorphism, solvatomorphism effects, and interactions in lipid membranes. 32,33 Moreover, the dual uorescence effect of 1,3,4-thiadiazole is an interesting phenomena which is very important in understanding protein interactions of this molecule in biological systems.…”

Magnetic response and its relation to the keto‐enol tautomerism of 3,3′‐(1,4‐phenylene)bis(pentane‐2,4‐dione): Experimental and theoretical insights

“…Keto‐enol tautomerism can be observed in 1,3‐diketo compounds and is characterized by an intramolecular proton transfer. [ 2 ] This phenomenon has attracted researchers' attention, as it allows predicting the physicochemical and biological properties of substances. [ 2,3 ] The robust chemical reactivity of this type of 1,3‐diketo compounds that show tautomerism allows them to be used in the synthesis of heterocyclic compounds or metal‐ligand coordination compounds.…”