Mercury(II) dithiocarbamates: Structural aspects and their use as single-source precursors for shape-controlled facile synthesis of HgS nanoparticles

Abstract

A single-source, precursor strategy has been adopted for the shape-controlled synthesis of HgS nanoparticles (NPs) in which Hg(II) dithiocarbamate complexes are used as the starting materials. The precursor complexes bis(4-benzhydrylpiperazine-1-carbodithioate-κ2 S,Sʹ)mercury(II), bis(4-benzylpiperazine-1-carbodithioate-κ2 S,Sʹ)mercury(II), bis(4-hydroyethylpiperazine-1-carbodithioate-κ2 S,Sʹ)mercury(II), bis(4-benzylpiperidine-1-carbodithioate-κ2 S,Sʹ)mercury(II) and propane-1,3-diyl-bis(piperidincarbamodithioate)mercury(II), termed as [Hg(L1)2] to [Hg(L5)2] respectively, were characterized by chemical analysis (CHNS), FT-IR, 1H and 13C NMR spectroscopy. Two of the complexes, [Hg(L1)2] and [Hg(L2)2], were also subjected to single-crystal XRD analysis to recognize their molecular and supramolecular features. The conversion of the precursor complexes to HgS NPs was achieved by their thermolysis in ethylenediamine (en) at ambient pressure and low temperature in the absence of any externally added toxic surfactant. The morphology, structure, phase and elemental composition of the resulting HgS NPs were analyzed by SEM, PXRD and EDS techniques. The SEM results revealed a significant precursor-based morphological variation in the HgS NPs, which could be attributed to the stability/solubility of the initial precursor complex in ethylenediamine and to the presence of a capping agent on the particle surfaces (as revealed by DFT studies and FT-IR analysis). The PXRD patterns showed that the HgS NPs grow in two typical cystalline forms - cubic (black) and hexagonal (red). The optical properties of the NPs were assessed by UV–Visible spectroscopy, which confirmed that they have a good absorption ability in the visible region.