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

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 νC–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.