Nickel(ii) dithiocarbamate complexes containing the pyrrole moiety for sensing anions and synthesis of nickel sulfide and nickel oxide nanoparticles

Abstract

New homoleptic complexes bis(N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamato-S,S′)nickel(II) (1), bis(N-(pyrrol-2-ylmethyl)-N-furfuryldithiocarbamato-S,S′)nickel(II) (2) and bis(N-(pyrrol-2-ylmethyl)-N-cyclopropyldithiocarbamato-S,S′)nickel(II) (3) and heteroleptic complexes (N-(pyrrol-2-ylmethyl)-N-butyldithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II) (4), (N-(pyrrol-2-ylmethyl)-N-furfuryldithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II) (5) and (N-(pyrrol-2-ylmethyl)-N-cyclopropyldithiocarbamato-S,S′)(thiocyanato-N)(triphenylphosphine)nickel(II) (6) have been prepared and characterized by elemental analysis, IR, ¹H, ¹³C NMR, HSQC, HMBC and UV-Vis absorption spectra. For the heteroleptic complexes, the thiocyanide ν_C–N values were shifted to higher wavenumbers and NCS₂ carbon signals were shifted downfield compared to that of homoleptic complexes, suggesting the increased strength of the thioureide bond due to the presence of π-accepting phosphine. Electronic spectral studies suggest square-planar geometry for the complexes. Complex 5 was also characterized by X-ray diffraction techniques and presents a distorted NiS₂PN square planar configuration around the Ni atom. Rare C–H⋯Ni intramolecular short contact interactions were observed in the complex 5. The ability of representative complexes 1 and 2 to sense anions (F⁻, Cl⁻, Br⁻ and I⁻) was examined by UV-Vis absorption spectra and cyclic voltametric titration studies. These studies show that both the complexes prefer to bind with I⁻. Complex 2 has been used as a single source precursor for the preparation of nickel sulfide and nickel oxide nanoparticles. The as-prepared nickel sulfide and nickel oxide nanoparticles have been characterized by PXRD, SEM, EDAX, TEM, HRTEM, UV-Vis and Photoluminescence spectroscopy. X-ray diffraction analysis showed the presence of three phases (cubic-NiS₂, cubic-Ni₃S₄ and rhombohedral-Ni₃S₂). TEM images of nickel oxide revealed that the particles are spherical in shape with diameter ∼30 nm.