title: 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.
authors.affiliation: Department of Biophysics, University of Life Sciences in Lublin , Akademicka 13, 20-950 Lublin, Poland.
authors.forename: Arkadiusz
authors.identifier: http://orcid.org/0000-0003-2630-120X
authors.initials: A
authors.lastname: Matwijczuk
authors.affiliation: Department of Analytical Chemistry (C1), Faculty of Chemical Engineering and Technology, Krakow University of Technology , Warszawska 24, 31-155 Krakow, Poland.
authors.forename: Dariusz
authors.initials: D
authors.lastname: Karcz
authors.affiliation: Department of Biophysics, University of Life Sciences in Lublin , Akademicka 13, 20-950 Lublin, Poland.
authors.forename: Radosław
authors.initials: R
authors.lastname: Walkowiak
authors.affiliation: Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University , Gronostajowa 7, 30-387 Kraków, Poland.
authors.forename: Justyna
authors.initials: J
authors.lastname: Furso
authors.affiliation: Department of Physics, University of Life Sciences in Lublin , Akademicka 13, 20-950 Lublin, Poland.
authors.forename: Bożena
authors.initials: B
authors.lastname: Gładyszewska
authors.affiliation: Department of Analytical Chemistry (C1), Faculty of Chemical Engineering and Technology, Krakow University of Technology , Warszawska 24, 31-155 Krakow, Poland.
authors.forename: Sławomir
authors.initials: S
authors.lastname: Wybraniec
authors.affiliation: Institute of Industrial Organic Chemistry , Annopol 6, 03-236 Warsaw, Poland.|Department of Chemistry, University of Life Sciences in Lublin , 20-950 Lublin, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Niewiadomy
authors.affiliation: Aleksander Jabłoński Institute of Physics, Nicolaus Copernicus University , 87-100 Toruń, Poland.
authors.forename: Grzegorz P
authors.initials: GP
authors.lastname: Karwasz
authors.affiliation: Department of Cell Biology, Institute of Biology, Maria Curie-Skłodowska University , 20-033 Lublin, Poland.
authors.forename: Mariusz
authors.initials: M
authors.lastname: Gagoś