The interplay of secondary Hg⋯S, Hg⋯N and Hg⋯π bonding interactions in supramolecular structures of phenylmercury(ii) dithiocarbamates

Abstract

Three new phenylmercury(II) and one mercury(II) dithiocarbamate complexes viz.PhHg S₂CN(PyCH₂)Bz (1), PhHg S₂CN(PyCH₂)CH₃ (2), PhHg S₂CN(Bz)CH₃ (3), and [Hg (NCS₂(PyCH₂)Bz)₂] (4) (Py = pyridine; Bz = benzyl) have been synthesized and characterized by elemental analyses, IR, electronic absorption, ¹H and ¹³C NMR spectroscopy. The crystal structures of 1, 2 and 3 showed a linear S–Hg–C core at the centre of the molecule, in which the metal atom is bound to the sulfur atom of the dithiocarbamate ligand and a carbon atom of the aromatic ring. In contrast the crystal structure of 4 showed a linear S–Hg–S core at the Hg(II) centre of the molecule. Weak intermolecular Hg⋯N (Py) interactions link molecules into a linear chain in the case of 1, whereas chains of dimers are formed in 2 through intermolecular Hg⋯N (Py) and Hg⋯S interactions. 3 forms a conventional face-to-edge dimeric structure through intermolecular Hg⋯S secondary bonding and 4 forms a linear chain of dimers through face-to-face Hg⋯S secondary bonding. In order to elucidate the nature of these secondary bonding interactions and the electronic absorption spectra of the complexes, ab initio quantum chemical calculations at the MP2 level and density functional theory calculations were carried out for 1–3. Complexes 1 and 2 exhibited photoluminescent properties in the solid state as well as in the solution phase. Studies indicate that Hg⋯S interactions decrease and Hg⋯N interactions increase the chances of photoluminescence in the solid phase