Hydrothermal synthesis of (C5H14N2)[CoCl4]? 0.5 H2O: Crystal structure, spectroscopic characterization, thermal behavior, magnetic properties and biological evaluation

The organic-inorganic compound (C5H14N2)[CoCl4]?0.5H2O, I, was characterized by various physicochemical techniques. The X-ray diffraction analysis revealed that the compound crystallizes in the centrosymmetric space group C2/c of the monoclinic system. The atomic arrangement the Co(II) complex is built from isolated [CoCl4]2? anions, 1-methylpiperazine-1,4-diium [C5H14N2]2+ cations and free water molecules. The crystal structure study showed that the cohesion of I is assured through N?H???Cl and N?H???O hydrogen bonds giving birth to a 3-D architecture. Hirshfeld surface analysis revealed that Cl???H/H???Cl and H???H (58.5 and 36.4%, respectively) are the most significant interactions between species. Minor O???H/H???O interactions are also present. The compound was characterized by thermal analysis, TGA-DTA showed the removal of the co-crystallized water before 100 ?C and a first mass loss at around 120 ?C. Magnetic measurements are in good agreement with isolated, S = 3/2, tetrahedral [CoCl4]2? anions. The negative Weiss constant of -1.35 indicates single-ion anisotropy and very weak antiferromagnetic interactions. UV?visible spectroscopy reveals three weak absorption bands in the visible range due to the d-d electronic transitions typical of the Co(II) tetra-coordinated. A bioassay showed antibacterial activity against the gram negative Klebsiella pneumonia and gram positive Bacillus ceureus, Listeria monocytogenes, and Micrococcus lutues.