Mono and trivalent thallium–sulfur interactions and their influence on the formation of nano thallium sulphide: single crystal X-ray structural and spectral studies on thallium(i)/(iii)–cyclohexylpiperazine dithiocarbamates

Abstract

Thallium(I) and thallium(III)–cyclohexylpiperazine dithiocarbamates have been prepared with the same donor environment for the first time and analyzed by electronic, IR, ¹H, ¹³C NMR spectral, CV and single crystal X-ray structural analyses. Solvothermal decomposition of the dithiocarbamates yielded nano Tl₄S₃ and were characterized. Bond parameters from single crystal X-ray structures have been used in continuous symmetry measure and bond valence sum analysis of the compounds to establish the octahedral geometry and formal oxidation numbers of thallium. [Tl(chpzdtc)]₂ (1) shows extensive non covalent interactions and the hemidirected TlS₂CSTl core is of distorted square pyramidal geometry with the stereo chemically active lone pair of thallium(I) occupying a vertex of the square pyramid. This is the first report which identifies the 4f_7/2 and 4f_5/2 electron binding energies of Tl(I) and Tl(III) dithiocarbamates unambiguously and the effect of Tl⋯C interaction on XPS binding energies. [Tl(chpzdtc)₃] (2), the trivalent analogue as a contrast is a typical holodirected TlS₆ distorted octahedral core with no significant supramolecular interactions. Mean Tl–S bond distances in 1 and 2 are 2.985(7) and 2.6789(19) Å, respectively, which clearly support the higher ease of solvothermal decomposition of 1 to nano Tl₄S₃ than 2. A strong correlation exists between the bond strengths of Tl–S, the thioureide C–N and the ease of formation of Tl₄S₃ from the two dithiocarbamates 1 and 2.