Structures and Properties of a Series of High-Spin [Co^II₂] Complexes Supported by Ancillary Benzoate, Ortho-Hydroxybenzoate, and Para-Hydroxybenzoate Ligands

Abstract

A new series of high-spin [CoII 2] complexes [Co2(cpdp)­(μ-O2CC6H5)] (1), [Co2(cpdp)­(μ-o-O2­CC6­H4­(OH))]·H2O (2), and [Co2(cpdp)­(μ-p-O2­CC6­H4­(OH))]·5H2O (3) of the carboxylate-affixed multidentate ligand, N,N′-bis­[2-carboxybenzomethyl]-N,N′-bis­[2-pyridylmethyl]-1,3-diaminopropan-2-ol (H3cpdp), have been synthesized and structurally characterized [C6H5CO2 – = benzoate; o-C6H4(OH)­CO2 – = ortho-hydroxybenzoate; p-C6H4(OH)­CO2 – = para-hydroxybenzoate]. In methanol, complexes 1, 2, and 3 have been synthesized by carrying out the reaction of H3cpdp with stoichiometric quantities of Co­(BF4)2·6H2O/C6H5CO2Na, Co­(BF4)2·6H2O/o-C6­H4­(OH)­CO2­Na, and Co­(BF4)2·6H2O/p-C6­H4­(OH)­CO2­Na respectively, in the presence of NaOH at room temperature. Complexes 1–3 have been characterized by microanalysis, molar conductance, FTIR and UV–vis, mass spectrometry, PXRD, thermogravimetric analysis, single-crystal X-ray diffraction studies, and variable temperature magnetic susceptibility measurements. In 1–3, the nonbonded Co···Co separations are 3.4311(8), 3.4551(8), and 3.4393(7) Å, respectively, and the Co­(II) ions are doubly bridged by one alkoxide group of the multidentate ligand and one benzoate/ortho-hydroxybenzoate/para-hydroxybenzoate group. As disclosed by single-crystal X-ray analyses, all three complexes assume distorted trigonal bipyramidal geometry around each cobalt center under the N2O3 coordination environment provided by the cpdp3– ligand and the ancillary benzoate/ortho-hydroxybenzoate/para-hydroxybenzoate functionalities. The distorted trigonal bipyramidal geometry is further authenticated by SHAPE analysis of the Co­(II) coordination sphere. Magnetic susceptibility data were recorded for 1–3 in the temperature range of 2–300 K, and their analysis has disclosed the occurrence of antiferromagnetic interactions, associated with the spin-orbit coupling effect. The nature and mechanism of magnetic interactions are discussed on the basis of magneto-structural parameters, and these are mainly correlated with the magnitude of Co–Obridging alkoxide–Co angles. Moreover, with the aim of reducing toxicity and irritation of free cobalt­(II) ion in the tissues, all three organo-chelated [CoII 2] complexes were evaluated as antibacterial agents against Staphylococcus aureus, SA96, which is known to cause several life-threatening chronic infections and diseases. The antibacterial studies revealed that all three complexes are significantly active against this bacterial strain showing minimum inhibitory concentration values in the range of 300–600 μg/mL. However, a comparative assessment of their biological efficacies revealed that 2 and 3 exhibited higher antibacterial activity compared to that of 1.

Unraveling Multicopper [Cu3] and [Cu6] Clusters with Rare μ3-Sulfato and Linear μ2-Oxido-Bridges as Potent Antibiofilm Agents against Multidrug-Resistant Staphylococcus aureus

“…Owing to their structural diversity, specificity, and water-solubility, carboxylate-based multimetallic compounds are valuable entities for developing antibiofilm agents. The decision to explore the present research work was based on previous studies in our group that analyzed systematic biological properties of a number of Zn­(II) and Co­(II) complexes. − It is strongly believed that during interactions of different biomolecules such as DNA and protein with metal clusters, the consequence of the adjoining metal center cannot be disregarded. Normally, the interaction of a biomolecule with one metal center is assisted by the electrostatic outcome of the adjoining metal center.…”

Halide mediated modulation of magnetic interaction and anisotropy in dimeric Co(ii) complexes

“…Furthermore, exploring the influence of various ligands in facilitating ferro- or antiferromagnetic interactions, whether exchange or dipole–dipole in nature, would be valuable. 32,33 While O-based bridges have been prevalent in SMM chemistry, alternative bridging groups are gaining popularity, offering intriguing magnetic properties and substantial anisotropic energy barriers, and magnetic anisotropy generated by 3d metal ions with specific coordination geometry leads to an increase in overall magnetic anisotropy with a higher effective energy barrier. 34 However, constructing these complexes as predicted presents challenges due to factors such as the ligand-to-metal ratio, bridging group nature, solvent conditions, pH, and temperature.…”