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VOL. 10, ISSUE 2 (2026)
Synthesis of Mn (II) & Fe (II) metal complexes containing polyphosphonic acid ligands
Authors
Bipin Bahadur Saxena, Vipin Kumar Singh, S S Khirwar, Devendra Kumar Singh
Abstract
The synthesis, structural characterization, and property evaluation of
novel Manganese (II) and Iron (II) metal complexes using polyphosphonic acid
ligands are presented in this study. Crystallographic bulk substances and
individual crystals suitable for XRD were effectively isolated via benchtop
solution precipitation and Teflon-lined hydrothermal methods, respectively. The
synthesis of the Iron (II) derivatives was carried out under a strict anaerobic
nitrogen atmosphere to prevent the atmospheric oxidation of the phosphonate
arms without causing metal-hydroxide precipitation. Complexation was verified
by FT-IR spectroscopy, which revealed modifications in the ν(N-H) and ν (O-H)
regions as well as a distinctive shift of the v(P=O) stretching bands to lower
wavenumbers (30–50 cm⁻¹). TGA made a distinction between directly coordinated
water molecules (stable up to 150–250°C) and weakly bound lattice water
molecules (lost at 50–120°C). According to magnetic susceptibility
measurements, both metal centers exhibit collective ferromagnetic exchange
interactions at low temperatures mediated by the bridging phosphonate oxygen
pathways, adopting a high-spin configuration at room temperature (μeff
~5.92μB for Mn²⁺ and ~4.90μB for Fe2+).
Additionally, structural investigation showed that large, dense supramolecular
hydrogen-bonding networks are formed by uncoordinated phosphonate hydroxyl and
amine groups. The promise of these complexes as functional materials for
solid-state proton conductivity and molecular magnetic applications is
highlighted by their extended networks, which solidify the crystal matrices
into 2D layers or 3D frameworks.
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Pages:126-132
How to cite this article:
Bipin Bahadur Saxena, Vipin Kumar Singh, S S Khirwar, Devendra Kumar Singh "Synthesis of Mn (II) & Fe (II) metal complexes containing polyphosphonic acid ligands". International Journal of Chemistry Studies, Vol 10, Issue 2, 2026, Pages 126-132
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