Syntheses, crystal structures, optical and antibacterial properties of two organic-inorganic hybrids containing pyridinium-substituted triphenylphosphonium and tetrachlorocobaltate/copperate(II)

In this article, we present the syntheses, crystal structures, vibrational spectra, optical and antibacterial properties of two new organic-inorganic hybrids, [Py(CH2)3TPP][CoCl4]·H2O (1) and [Py(CH2)3TPP][CuCl4] (2), where [Py(CH2)3TPP]2+ was 1-(1′-pyridyl-propyl)-3-triphenyl phosphonium. Two hybrids were crystallized in the monoclinic space group P21/n. The hybrids consisted of a [Py(CH2)3TPP]2+ cation and a tetrahedral [CoCl4]2−/[CuCl4]2− anion, where the crystal structure was stabilized by C−H···Cl, O−H···Cl, and C−H···O hydrogen bonds due to the presence of a water molecule in 1, and the crystal structure of 2 was stabilized by C−H···Cl hydrogen bonds. Experimental vibrational bands (IR and Raman) have been discussed and assigned. The intermolecular energy, the energy gap between HOMO and LUMO orbitals, as well as the first hyperpolarizabilities were predicted based on DFT calculations. The low energy gaps (1.26 eV for 1 and 1.20 eV for 2) were responsible for the charge transfer interactions that eventually occur between the cation and anion. The first hyperpolarizabilities (βtot) of 1 and 2 were 82 and 237 times as high as that of the standard KDP crystal, respectively, indicating that the as-prepared hybrids were excellent materials for NLO applications. Furthermore, it was found that both salts exhibit good bactericidal activity against Escherichia coli and Staphylococcus aureus.