Syntheses, crystal structures, antibacterial activities and non-linear optical properties based on DFT calculation of two substituted benzyl piperidinium salts tetrahalogenated copper(II)

Abstract

This paper presents the syntheses, composition analysis and structural characterization of two ionic complexes, [4NO2BzPid]2[CuX4] ([4-NO2BzPid]+= 4-nitro-1-benzylpiperidinium, X = Cl(1) and Br(2)). Two complexes crystallize in chiral space group P6(4)(No. 172), and comprise two [4NO2BzPid]+cations and a [CuX4]2– anion in which the piperidine ring shows a boat structure while the [CuX4]2– anion exhibits a tetrahedron geometry. The intermolecular energy, the energy gap between the HOMO and LUMO orbitals, and the first hyperpolarizability were carried out based on the DFT calculation. The low energy gap (2.24 ev for 1 and 2.01 ev for 2) explains the eventual charge transfer interactions taken place between the [CuX4]2−anion and [4NO2BzPid]+cation. The first hyperpolarisability (βtot) of two salts is 9.3 and 16.0 times greater than that of the standard KDP crystal showing that two complexes are good materials for NLO application. The results of antibacterial experiments show that two complexes exhibit good bactericidal activity for S. aureus and E. coli.