Crystal structure, optical, magnetic and antibacterial properties of a new tetrachlorocobaltate(II) salt with 4-nitrobenzyl substituted 2-methyl pyridinium

Abstract

In this paper, a new organic-inorganic hybrid crystal material, 4-nitrobenzyl-2-methylpyridinium tetrachlorocobaltate(II) [4-NO2Bz-2-MePy]2[CoCl4](1), had been obtained by the slow-evaporation solution growth method. The single-crystal X-ray diffraction analysis showed that 1 crystallized in the monoclinic space group P21/n, composed of two [4-NO2Bz-2-MePy]+ cations and a [CoCl4]2− anion, where the cations represented Λ-shaped structure and the [CoCl4]2− anions exhibited a tetrahedral geometry. The PXRD spectrum confirmed the bulk phase purity, homogeneity, and crystalline nature of the material. The HOMO-LUMO energy gap and UV-visible diffuse reflectance spectrum explained the charge transfer interactions between the [CoCl4]2− anions and the [4-NO2Bz-2-MePy]+ cations. Furthermore, the low band gap values (1.27 eV for the experimental value and 1.65 eV for the calculated value) indicated the appropriateness of the crystal for optical applications. The first hyperpolarizability (βtot) of the salt was more than 6600 times higher than the standard KDP crystal (βKDP = 6.85 × 10−31 esu), suggesting that the title crystal was a superior material for NLO applications. The results of the antimicrobial experiment revealed that the compound exhibited excellent antimicrobial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The title salt displayed weak antiferromagnetic interaction with the lowering of temperature.