Mercury(II) N,N′-diarylformamidine dithiocarbamates as single-source precursors for the preparation of oleylamine-capped HgS nanoparticles

Abstract

Mercury(II) complexes of N,N′-diarylformamidine dithiocarbamate of the general formula [Hg-(L)2] (L = N,N′-bis(2,6-dimethylphenyl)formamidine dithiocarbamate L1 (1), N,N′-bis(2,6-disopropylphenyl) formamidine dithiocarbamate L2 (2), N,N′-mesityl formamidine dithiocarbamate L3 (3), N′-(2,6-dichlorophenyl-N-(2,6-dimethylphenyl) formamidine dithiocarbamate L4 (4), N′-(2,6-dichlorophenyl)-N-(2,6-diisopropylphenyl) formamidine dithiocarbamate L5 (5) and N′-(2,6-dichlorophenyl)-N-mesityl formamidine dithiocarbamate L6 (6)) have been synthesized and characterized by physicochemical and spectroscopic techniques. The molecular structures of 1, 2 and 6 were unequivocally determined using single-crystal X-ray diffraction as mononuclear species in which the Hg(II) centers are coordinated to four sulfur atoms from two dithiocarbamate ligands resulting in distorted square planar geometries. Complexes 1, 3 and 6 were used as single-source precursors to prepare mercury sulfide nanoparticles HgS1, HgS3 and HgS6 in oleylamine which acted as the solvent as well as the capping agent. HR-TEM images of HgS1, HgS3 and HgS6 particles are nanospherical in shape with size distribution between 5 and 16 nm. Powder XRD pattern confirmed the β phase (metacinnabar) of HgS in all the nanoparticles with an average crystallite size similar for HgS1 and HgS3, 9.35 and 9.46 nm, respectively, and smaller crystallite sizes, 5.15 nm for HgS6. The optical properties information obtained from the UV–visible and photoluminescence spectra of the HgS nanoparticles showed evidence of quantum confinement.