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An experimental and theoretical study of the molecular structure of an organic arsenate templated by 4-aminopyridine, with the general formula (C5H7N2)(C5H8N2)[AsO4]·H2O ((4-APH)(4-APH2)[AsO4]·H2O), is presented. The optimized geometry, vibrational frequencies and various thermodynamic parameters of the title compound calculated using DFT methods are in agreement with the experimental values. The theoretical calculations were performed using density functional theory (DFT) method at B3LYP/6-311 + + G(d,p) basis set levels. A detailed interpretation of the IR and Raman spectra were reported. The thermodynamic functions (heat capacity, entropy, and enthalpy) from spectroscopic data by statistical methods were obtained for the range of temperature 100–1000 K. The molecular orbital calculations such as Natural Bond Orbitals (NBOs), AIM approach, HOMO-LUMO energy gap, Molecular electrostatic potential (MEP), NLO characteristic and Hirshfeld surface analysis were performed with the same DFT level. Electronic stability of the compound arising from hyper conjugative interactions and charge delocalization were investigated based on the natural bond orbital (NBO) analysis. The molecular docking simulation results showed an excellent agreement with the experimental findings and satisfactory support the antiviral effects, the druggability and pharmacokinetic properties of the compound.

A new mononuclear cobalt hybrid material (C6H9N2)2[CoCl4] was prepared using slow evaporation technique at room temperature. The X-ray diffraction analysis revealed that the compound crystallizes in the centrosymmetric space group P-1 of the triclinic system. In the crystal structure, the atomic arrangement is described as an alternation of 0-Dimensional organic and inorganic stacks; these stacks are connected via hydrogen bonds. The supramolecular architecture is stabilized by intermolecular interactions such as π···π stacks and halogen···halogen interactions. Hirshfeld surfaces and the breakdown of the fingerprint plots were determined to quantify the intermolecular contacts present in the crystal lattice. The thermal decomposition was studied by DSC and TGA techniques. The optical band gap energy suggests the semiconductor nature of the complex. The in-vitro biological activities show that the compound is a promising antioxidant agent.

Two polymorphs of the new complex (C13H22N)2[CoBr4] have been prepared. The crystal structures of the polymorphs were determined by X-ray crystallography. Polymorph I belongs to the triclinic system, space group P-1 (No 2), while polymorph II adopts the monoclinic space group P21/c (No 14). The crystal packing is guided by C H···Br hydrogen bonds; these interactions contribute to the overall stabilization of the structures as they connect anions and cations together into a three-dimensional network. The polymorphs present different structure-properties relationships. Hirshfeld surfaces analysis contributes to the identification of the primary intermolecular contacts that guide the packing diagram. The thermal decomposition was studied by DSC, VT-PXRD, TDA and TGA techniques. The optical band gap energy suggests the semiconductor nature of the polymorphs. Temperature dependent magnetic susceptibility measurements in the temperature range of 1.8–310 K reveal that the polymorphs exhibit very weak antiferromagnetic interactions or contributions from single ion anisotropy.

Three complexes with the general formula (C 6 H 9 N 2 ) 2 [M II Br 4 ] with M II = Cu (1), Co (2) and Zn (3) have been grown by the slow evaporation method at room temperature. These compounds were subjected to the following characterization techniques: single crystal X-ray diffraction, thermal analysis (ATG-TD), In situ X-ray powder diffraction and temperature dependent magnetic susceptibility measurements. The crystals of (C 6 H 9 N 2 ) 2 [CuBr 4 ] belong to the triclinic P 1 ¯ space group, whereas (C 6 H 9 N 2 ) 2 [CoBr 4 ] and (C 6 H 9 N 2 ) 2 [ZnBr 4 ] crystallize in the orthorhombic system with the Pbcn space group. Molecular structures of the three coordination compounds consist of [MBr 4 ] 2- anions and 2-amino-6-methylpyridinium cations linked together via non-covalent interactions including hydrogen bonding, π···π stacking and halogen···halogen interactions which lead to three-dimensional supramolecular architecture. The thermal decomposition of the copper compound reveals the slow crystallization of CuBr at 130 °C. Both compounds 1 and 2 exhibit weak antiferromagnetic interactions.