Synthesis, structural diversity, and methanol vapor adsorption properties of three Hg(II) halide complexes derived from a helical Schiff base

The Schiff base condensation reaction between precursor diamine N,N'-bis(2-aminophenyl)-pyridine-2,6-dicarboxamide and 1,8-naphthyridine-2-carbaldehyde yielded a racemic compound (L^P/L^M), which was characterized by ¹H/¹³C NMR, infrared spectroscopy, elemental analysis, and single crystal X-ray diffraction. Three complexes, [Hg₂LI₄] (1), [Hg₂LBr₄] (2), and [Hg₂L₂Cl₄]‧2H₂O (3) with different coordination configurations were obtained from the reaction of this compound with HgX₂ (X = I⁻, Br⁻, and Cl⁻), respectively, and their crystal structures and coordination geometries were determined via single crystal X-ray diffraction techniques. Both 1 and 2 exist as dinuclear complexes with a 1:2 molar ratio of L and Hg(II), while 3 exists as a 44-membered metallamacrocycle with a 1:1 molar ratio of L and Hg(II). The structural diversity of these three complexes indicates that the counter anions have significant effects on the structural topology. In addition, the solid-state luminescence and the gas adsorption of these complexes towards methanol vapor at room temperature were investigated.