Crystal Structure, Hirshfeld Surface, Vibrational Study, Optical Properties and Biological Activities of a Novel Hybrid Material 2-Methylpiperazine-1,4-Dium Tetrachlorocobaltate(II) based on DFT Calculation

A new (C₅H₁₄N₂)CoCl₄ compound was synthesized by slow evaporation at room temperature. Asymmetric unit of this compound consists of one tetrahedral geometry [CoCl₄]^2- and one diprotonated organic cations. The structure consists of an alternation along the a-axis of organic-inorganic layers parallel to (a, b) plane. The inorganic layers built up of isolated tetrahedral [CoCl₄]^2-. Crystal packing is stabilized by electrostatic interactions and hydrogen bonds between cations and anions. Hirshfeld surface was conducted to investigate intermolecular interactions. Density Functional Theory (DFT) calculations of geometry optimization, vibrational frequencies, simulated UV-Visible spectrum, Frontier molecular orbitals analysis, nonlinear optical properties were made together with the experimental studies. Good agreement was found between theoretical and experimental results. In fact, the second hyperpolarizability value 〈γ〉 of compound (0.8665 × 10^-36 esu) indicates that hydrogen bonds play an important role in the creation of crystal structure, its stability and in the enhancement of polarizability α and hyperpolarizability of crystal. Hence, the large 〈γ〉 value suggests that this compound is a Non-Linear Optical (NLO) material of interest and could be adopted in various optical applications. Energy gap indicates that our compound behaves as a semi-conductor material. In the other hand, the bioassay results showed that this structure exhibits significant antioxidant and antibacterial activities.