New sulfonic derivatives of quercetin as complexing reagents: synthesis, spectral, and thermal characterization

Abstract

The synthesis conditions of quercetin-8-sulfonic acid and sodium salt of sulfonated quercetin were determined. The molecular formulae of obtained compounds are: C 15 H 10 O 10 SÁ4H 2 O and C 15 H 9 O 10 SNaÁ4H 2 O. On the basis of spectral methods UV-Vis, IR, and 1 H NMR it was stated that the sulfonation of quercetin occurs at 8-C position of the A ring. The complexing properties of Na-QSA-8 were confirmed by synthesis of a solid complex with Fe(II) ions. The NaQSA-8 formed a complex with Fe(II) ions at pH 5 with the metal excess (c M :c L = 7:1). The chelation site was analyzed using spectroscopy methods. It was found that chelation of the metal ions occurs at the 4C=O, 3-OH and 3 0 -OH, and 4 0 -OH sites of the molecule NaQSA-8. Thermal decomposition of the compounds was carried out in air and nitrogen gas carries. The TG-FTIR-MS technique was employed to study decomposition pathway. The dehydration process was discussed in relation to of the nature of water contained in the compounds.

Gallic Acid and Quercetin as Intelligent and Active Ingredients in Poly(vinyl alcohol) Films for Food Packaging

“…Aromatic ring stretch bands for C=C were detected at 1610, 1561, and 1520 cm −1 . The signal for ν(C-O) can be found at 1462 cm −1 [37], other bands associated with the vibrations of C-O bonds appear also at 1132 cm −1 (C-OH stretching). The in-plane bending band of C-H in aromatic hydrocarbon was detectable at 1318 cm −1 , and out-of-plane bending bands were evident at 930, 822, 678, and 603 cm −1 .…”

Spectroscopic, thermogravimetric and biological studies of Na(I), Ni(II) and Zn(II) complexes of quercetin

“…According to the literature data, other metal complexes of quercetin showed similar thermal behavior. The thermogravimetric analysis of the sodium(I) salt and Fe(II) complex of sulfonic derivative of quercetin revealed that these compounds underwent one step dehydration in the temperature range 20-150°C for sodium salt (loss of four water molecules) and 20-160°C for the iron complex (loss of 12 molecules of water) [32]. The increase of temperature in the range of 150-560°C caused the decomposition of the anhydrous compounds.…”

Synthesis, spectral and thermal study of La(III), Nd(III), Sm(III), Eu(III), Gd(III) and Tb(III) complexes with mefenamic acid

“…Low values of dehydration enthalpies indicate that the water molecules are weakly bonded to the ligand and probably participate in the formation of hydrogen bond with mefenamate ligand. Hence, the obtained lanthanide compounds contain only crystallization water molecules [49,50]. After dehydration step, the resulting anhydrous compounds are stable up to about 350°C.…”