Role of non-covalent interactions in the supramolecular architectures of Co(II), Cu(II), Zn(II), and Cd (II) based complexes with heterofunctional ligand (2-amino, 5-nitrobenzoic acid): Comparative experimental and Hirshfeld surface calculations

Four novel monomeric metal complexes based on heterofunctional ligand (2-amino, 5-nitro benzoic acid (L1H)), namely {[Co(L1)₂.(H₂O)₄].4H₂O} (I), [Cu(L1)₂.(H₂O)₂] (II), [Zn(L1)₂.(H₂O)₂] (III), and [Cd(L1)₂.(H₂O)₂] (IV), have been synthesized under hydrothermal conditions. The crystal structures of monomeric complexes have been determined by single-crystal X-ray diffraction analysis and further characterized by elemental analyses, Infrared (IR) spectra, and thermogravimetric analysis (TGA). Among all these complexes, hydrogen bonding is the most important part in crystal structure explanation, along with the coordination mode of binding. All these complexes are stabilized collectively by covalent, and intermolecular hydrogen bonding interactions. The results demonstrated that the coordinated and lattice water molecules are useful for the stabilization of crystal structure. Focusing on this organic ligand (L1H), which has carboxylate, nitro, and amino functional groups that are exclusively able to form dative bonds as well as H-bonds in such a way that the hydrogen-bonding arrays can control 1D, 2D, and 3D structures. The Hirshfeld surface calculations revealed that the closest contacts of the complexes are dominated by H···H, H···O, N···H, CH···π and π···π (CC) interactions. The complexation of L1H with transition metals leads to the decrease of O···H, CH···π, and π···π interactions while increasing HH, and CO contacts.