Application of ultrasound to the synthesis of a new nanostructured Mn(II) supramolecular compound: A precursor for γ-Mn2O3 nanoparticles

• Nanostructures of [Mn(hpydcH2)2(H2O)4] were synthesized using a sonochemical technique.
• Using X-ray crystallography, a novel mode of coordination was revealed for the hpydcH3 ligand.
• The γ-Mn2O3, a rare form of manganese (III) oxide, was prepared in nanoscale.

A new nanostructured Mn(II) supramolecular compound [Mn(hpydcH2)2(H2O)4] (1) (hpydcH3 = 4-hydroxy-2,6-pyridinedicarboxylic acid) has been synthesized using a sonochemical process. The structure of compound 1 was determined by single crystal X-ray diffraction and it was revealed that each hpydcH2− anionic ligand has been coordinated to Mn(II) ion in a novel monodentate fashion leaving another functional carboxylic acid group intact. Compound 1 was also characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRPD), FT-IR spectroscopy and elemental analysis. Thermal stability of compound 1 was studied by thermal gravimetric (TG) analysis and compared to that of its crystalline analogue. Subsequently, the role of concentration of the initial reactants on the size of nanostructures of compound 1, has been investigated. Compound 1 was proved to be a precursor for γ-Mn2O3 nanoparticles.