Open Access Received: 02 June 2026   |   Accepted: 28 August 2026   |   Published: 07 September 2026

SYNTHESIS, COORDINATION STRUCTURE AND PHYSICOCHEMICAL PROPERTIES OF Fe(II)/Fe(III)–Zn(II) HETERONUCLEAR POLYGALACTURONATE COMPLEXES

Madina T. Xanabatova, Mokhira M. Nurmatova

Fergana State University, Fergana, Uzbekistan

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Abstract. Iron deficiency remains one of the most widespread nutritional disorders globally, leading to impaired oxygen transport, reduced physical work capacity, and systemic physiological dysfunction. Conventional low-molecular-weight iron supplements often present significant pharmacological limitations, including low bioavailability, rapid oxidation of bioactive Fe(II), poor gastrointestinal tolerance, and uncontrolled ion release. To overcome these challenges, natural polymeric ligands such as polygalacturonic acid (PGA) are used as macromolecular carriers. In this work, we report the synthesis, structural organization, and physicochemical characterization of novel heteronuclear Fe(II)/Fe(III)–Zn(II) polygalacturonate complexes. Synthesized via controlled interaction in aqueous media under regulated pH and molar ratios, these macromolecular systems combine iron and zinc ions within a single pectin-derived matrix. Fourier-transform infrared spectroscopy (FTIR) confirmed the direct coordination of carboxylate groups (COO-) with Fe and Zn centers, evidenced by characteristic shifts in asymmetric and symmetric stretching vibrations. X-ray diffraction (XRD) and thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) demonstrated that heteronuclear cross-linking alters the macromolecular ordering and significantly increases thermal stability compared to native PGA. Inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray photoelectron spectroscopy (XPS) revealed controlled stoichiometry and stabilized Fe(II)/Fe(III) oxidation states within the coordination network. The integration of Fe and Zn within a polygalacturonate framework provides controlled solubility and metal-release kinetics under physiologically relevant conditions, indicating their potential applicability in biomedical and nutraceutical formulations.

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Key words. Polygalacturonic acid; Heteronuclear complexes; Iron deficiency; Zinc coordination; Biopolymers; Thermal stability; Passivation and controlled release


DOI: 10.66640/UJP-2026-5-00015

*Corresponding author: Madina T. Xanabatova, Fergana State University, Fergana, Uzbekistan

Citation: Madina T. Xanabatova, Mokhira M. Nurmatova, SYNTHESIS, COORDINATION STRUCTURE AND PHYSICOCHEMICAL PROPERTIES OF Fe(II)/Fe(III)–Zn(II) HETERONUCLEAR POLYGALACTURONATE COMPLEXES. Uzbekistan Journal of Polymers, Vol. 5(3) 2026: pp.22-35. DOI: 10.66640/UJP-2026-5-00015

©2026 Uzbekistan Journal of Polymers