Síntese e caracterização estrutural de polímeros de coordenação de Sn(II) com ligantes carboxilatos

Abstract

Sn(II) coordination polymers (CPs) with carboxylate ligands represent a promising class of materials due to the unique combination of structural versatility and the stereochemical influence of the Sn(II) 5s² lone pair. This work aimed to synthesize and characterize new Sn(II) CPs, investigating how different carboxylic acids influence the dimensionality, geometry, and stability of the resulting networks. Hydrothermal routes were employed, using SnSO₄ and four distinct ligands: H₄MHNC, H₂IDC, H₂bpydc-5,5’, and H₂bpydc-6,6’. The materials were characterized by powder X-ray diffraction (PXRD), three-dimensional electron diffraction (3D-ED), Fourier-transform infrared spectroscopy (FTIR), and thermogravimetric/differential scanning calorimetry (TGA/DSC). The results revealed the formation of diverse structures, including one-, two-, and three-dimensional polymers, as well as the occurrence of disphenoidal and unusual penta-coordinated geometries for Sn(II). In some cases, partial oxidation of tin to Sn(IV) was observed, highlighting the challenge of stabilizing this cation under hydrothermal conditions. Thermal analysis indicated significant compound stability up to intermediate temperatures. It can be concluded that the nature and geometry of the ligands were decisive for the formation of the observed topologies and for the stability of the obtained CPs. This work broadens the understanding of Sn(II) coordination chemistry, evidencing both its structural diversity and the synthetic challenges involved, while also pointing to potential applications in catalysis and the development of new functional materials.