Theoretical, Spectroscopic and Crystal Structure Investigation of a Novel Selenomolybdate (NH4)4[Se2Mo5O21]·3H2O

The current investigation undertakes the synthesis, crystal structure, spectroscopic, thermal analyses and theoretical calculations of a new 3 D Strandberg-type polyoxometalate-based inorganic (NH4)4[Se2Mo5O21]·3H2O (denoted as ASH). Structural data obtained by single crystal X-ray diffraction revealed that the titled compound crystallizes in orthorhombic system with Pbcn space group, having parameters a = 15.0927(2) Å, b = 13.3633(1) Å, c = 23.8204(3) Å and Z = 8. Molecular structure and spectroscopic analysis were performed using experimental techniques like X-ray diffraction, infrared spectrum, UV–visible spectroscopy and thermogravimetric analysis. Hirshfeld surface analysis was performed to study the intermolecular interactions. The structural arrangement is mainly made by a system of H-bonds. All Strandberg clusters anions [Se2Mo5O21]4– are connected to each other through water molecules and the ammonium groups NH4+ to build a 3D (3 dimensional) supramolecular framework. Theoretical calculations were performed using PM3 semi-empirical model and several properties were studied.