Two new coordination compounds of Mn(II) and Cu(II) viz. [Mn(bz)2(Hdmpz)2(H2O)] (1) and [Cu(crot)2(Hdmpz)2] (2) (where, bz = benzoate, crot = crotonate, Hdmpz = 3, 5-dimethyl pyrazole) have been synthesized and characterized using single crystal X-ray diffraction technique, FT-IR, electronic spectroscopy, TGA and elemental analyses. Compounds 1 and 2 crystallize as mono-nuclear coordination compounds of Hdmpz based penta-coordinated Mn(II) and hexa-coordinated Cu(II) respectively containing distorted trigonal bipyramidal and distorted octahedral geome-tries. Crystal structure analysis of compound 1 reveals the presence C‒H⋯π and π-stacking in-teractions along with O‒H⋯O, N‒H⋯O and C‒H⋯O H-bonding interactions which stabilizes the layered assembly of the compound. Similarly, the presence of hydrogen bonding along with π-stacking interactions stabilizes the crystal structure of compound 2. We have carried out theo-retical investigations to analyze π⋯π H-bonding and antiparallel CH···π non-covalent interac-tions observed in the compounds. DFT calculations were performed to evaluate strength of these interactions energetically. Moreover, QTAIM and non-covalent interaction (NCI) plot index computational tool were used to characterize them and evaluate the contribution of the H-bonds.

Two new Mn(II) and Zn(II) metal-organic compounds of 1,10-phenanthroline and methyl benzoates viz. [Mn(phen)2Cl2]2-ClBzH (1) and [Zn(4-MeBz)2(2-AmPy)2] (2) (where, 4-MeBz = 4-methylbenzoate, 2-AmPy = 2-aminopyridine, phen = 1,10-phenanthroline, 2-ClBzH = 2-chlorobenzoic acid) have been synthesized and characterized using elemental analysis, TGA, spectroscopic (FTIR, electronic) and single crystal X-ray diffraction techniques. Crystal structure analysis of the compounds reveals the presence of various non-covalent interactions which provides stability to the crystal structures. Crystal structure analysis of the compound 1 reveals the formation of supramolecular dimer of 2-ClBzH enclathrated within the hexameric host cavity formed by the neighboring monomeric units. Compound 2 is a mononuclear compound of Zn(II) where flexible binding topologies of 4-CH3Bz is observed with the metal centre. Moreover various non-covalent interactions such as lp(O)-π, lp(Cl)-π, C‒H∙∙∙Cl, π-stacking interactions as well as N‒H∙∙∙O, C‒H∙∙∙O and C‒H∙∙∙π hydrogen bonding interactions are found to be involved in plateauing the molecular self-association of the compounds. The remarkable enclathration of the H-bonded 2-ClBzH dimer into a supramolecular cavity formed by two [Mn(phen)2Cl2] complexes has been further studied theoretically using density functional theory (DFT) calculations, non-covalent interaction (NCI) plot index and quantum theory of atoms in molecules (QTAIM) computational tools. Synergistic effects have been also analysed using molecular electrostatic potential (MEP) surface analysis.