Exploring supramolecular interactions between inorganic tetrachlorometallate and organic pyridinium dication: Synthesis, characterization and structural investigations

The crystal structures of three isostructural salts 2, 3 and 4 consisting of dication (α,α′-p-xylylene-N,N′-bis(3-hydroxymethylpyridinium) (L2+)), and tetrachlorometallates, [MCl4]2− (M = Co(II), Zn(II) and Cu(II) in 2, 3 and 4 respectively) have been reported. Synthesized salts are well characterized by various physico-chemical techniques such as CHN analysis, IR, TGA, DSC, NMR, PXRD and single crystal X-ray diffraction. The crystal lattice of complex 2 is constructed from two types of interactions viz., C–H⋯Cl and O–H⋯Cl H-bonding between the pyridinium dication and the complex anions [CoCl4]2−, whereas only C–H⋯Cl interaction was found to play major role in stabilizing the structures of organic inorganic hybrid complexes 3 and 4. The hierarchy of intermolecular interactions present in solid state, factors controlling the adopted structures of these compounds and their thermal stability are discussed in detail by using various analytical techniques including single crystal X-ray.