Crystallographic evidence of synthesized Ni(II) fluoride complex: Solubilization interaction of fluoride complex in anionic micellar media by conductometric and spectroscopic techniques

Abstract

The X-ray crystallographic and physicochemical investigation of newly synthesized coordination complex of nickel (Trans-difluorobis(N,N-dimethylethane-1,2-diamine-k2N,N')nickel(II)octahydrate [Ni(dmen)2F2].8H2O is encompassed in this manuscript. The synthesized complex was characterized by elemental analysis, FTIR studies, magnetic measurements, electronic absorption measurements, and single-crystal X-ray diffraction analysis. The crystals are monoclinic in the P2(1)/c space group, with a = 8.0271(4) Å, b = 4.4509(8) Å, c = 15.1013(11)Å, α = 90°, β = 113.2340(10)°, γ = 90°. The crystal structure displays O-H⋯F and O-H⋯O hydrogen-bond interactions. Solubilization of [Ni(dmen)2F2].8H2O (NiDC) by anionic surfactant, sodium lauryl sulfate (SLS), in aqueous solutions in the pre-micellar, micellar and post-micellar concentration ranges was accomplished by UV–Visible spectroscopy and electrical conductivity measurements. The thermodynamic parameters of complex-surfactant interaction including standard entropy (ΔSmic), free energy (ΔGmic), and enthalpy (ΔHmic) of micelle formation were evaluated. The disruption of structured water in the near environment of hydrophobic groups of the surfactant was responsible for the increase in critical micelle concentration (CMC) with increasing temperature. The negative values of ΔGmic and ΔHmic indicate that solubilization of complex in micelles was spontaneous, in addition to enthalpy and entropy-driven. UV–Vis spectroscopy revealed the quantitative measure of interaction of the complex with surfactant in terms of partition constant (Kx), the free energy of partition (ΔGpart), binding coefficient (Kbind), and binding free energy (ΔGbind). The presence of surfactant led to a red-shift in UV–Vis spectra of NiDC which indicates their strong interaction. From the outcomes of the study, it is very clear that CMC in pure surfactants was lower than the CMC found with Ni-complex. The NMR study revealed that the complex is resided at the palisade layer by interacting with the functional moieties of hydrophobic chain. This indication well coincides with results of partitioning study by UV–Vis spectroscopy. The complex also has significant antioxidant and hemolytic activity against DPPH and RBCs respectively but it has no cyctotoxicity against 3 T3 cell lines.