Novel crystal engineering of transition metal tetrachloride with protonated azoaromatic molecules

The tetrahedally coordinated crystalline salts of transition metal (Zn(II) and Hg(II)) tetrachlorides with protonated 1,2-bis(4-pyridyl)ethylene (bpe) and trans‐4,4′-azobispyridine (azp) reveal three supramolecular motifs: zig-zag chains, cyclic dimers and grommet chains linked by single N–H⋯Cl or N–H⋯Cl/C–H⋯Cl synthon. The present results enrich the reported assembling structure types of multicomponents by replacing 4,4′-bipyridine (bipy) with bpe and azp in complexing with metal chloride under acidic condition. The obtained crystals are all in monoclinic crystal system. The unit-cell dimensions of same metal coordinated with bpe and azp in HCl are similar. Crystalline salts of Zn(II) and Hg(II) tetrachlorides with H2bpe in HCl adopt C2/c space group, while those of Zn(II) tetrachloride in HCl and Hg(II) tetrachloride in AcOH with H2azp adopt P21/n space group. Furthermore, crystalline salt of Hg(II) with H2azp in HCl adopts C2 space group.