Lamellar and Supramolecular Feature of New Tutton’s Salts Incorporating 2-Amino-4-Methylpyrimidine: Thermal Stability, Optic Study, Antioxidant and Antimicrobial Activities

The slow evaporation reaction of 2-amino-4-methylpyrimidine and transition metal cation (MII = Fe and Ni) in the presence of sulfuric acid H2SO4 affords two novel double sulfate salts with similar general formula (C5H8N3)2[MII(H2O)6](SO4)2·2H2O (MII = Fe and Ni) abbreviated FePRM and NiPRM, respectively. Their structures have been determined by single-crystal X-ray diffraction analyses and further characterized by Infra-Red (IR) spectra, thermogravimetric analysis—differential scanning calorimetry (TG-DSC) and variable temperature powder X-ray diffraction (VT-PXRD) measurements. Structural characterization shows that the interplay of N–H···O, O–H···O and π···π interactions between lattice and coordinated water and ligands significantly contribute to the crystal packing leading to the formation and strengthening of three dimensional supramolecular assembly. Then, the structure exhibits lamellar topology where the interlayer distances are 13.065(4) and 13.138 (5) A for FePRM and NiPRM, respectively. Hirshfeld surface analysis employing 3D molecular surface contours and 2D fingerprint plots have been used to analyze the intermolecular interactions present in the crystals. The optical properties were characterized by UV–visible spectroscopy and the calculated band gap was estimated to be 3.91 and 4.08 eV for FePRM and NiPRM, respectively. In addition, the biological activities of the complexes were investigated through the scavenging effect on DPPH radicals, reducing and phosphonolybdonum assay as antioxidant activities.