MELAMINIUM DIHYDROGENPYROPHOSPHATE: SYNTHESIS, CRYSTAL PACKING, HIRSHFELD SURFACE ANALYSIS, AND REACTIVITY MAPPING: A COMBINED EXPERIMENTAL AND THEORETICAL STUDY

Abstract

This work presents the synthesis and multifaceted characterization of melaminium dihydrogenpyrophosphate, a novel organic-inorganic hybrid material showcasing the significant potential of nitrogen-rich heterocycles in crystal engineering and materials science. The melaminium cation, a robust heterocyclic building block, facilitates the formation of a stable three-dimensional architecture, as determined by single crystal X-ray diffraction (triclinic, space group P1‾‾). This framework is stabilized by an extensive network of strong hydrogen bonds and van der Waals forces, a finding corroborated by Hirshfeld surface analysis. Complementary density functional theory (DFT) calculations (B3LYP/lanl2dz) in aqueous solution showed excellent agreement with experimental structural data and revealed a remarkably narrow HOMO–LUMO energy gap (0.30 eV), indicative of high chemical reactivity. Molecular electrostatic potential (MEP) and electron localization function (ELF) analyses provided a detailed map of the charge distribution, identifying key reactive sites. Promising pharmacological properties were predicted through in silico studies, demonstrating high probabilities (Pa >0.7) for anticancer, antiangiogenic, and anti-inflammatory activities. Notably, molecular docking simulations against the TIE-2 receptor, a key target in tumor angiogenesis, revealed a superior binding affinity for MDP (–14.1 kcal/mol) compared to the known inhibitor rebastinib (–10.7 kcal/mol), underscoring its strong potential as a therapeutic agent. This study highlights the pivotal role of heterocyclic chemistry in designing functional hybrid materials with tailored structural, electronic, and biological properties.