Azo- and Hydrazo-Dipyridines in Halidometallate Structures

Document Type : Research Paper


University of Cologne, Faculty for Mathematics and Natural Sciences, Department of Chemistry, Institute for Inorganic Chemistry, Greinstraße 6, D-50939 Köln, Germany



From reaction mixtures containing 1,2-di(pyridin-Y-yl)diazene derivatives (“azopyridines”; Y,Y’-azpy; Y = 2, 3, or 4) and metal precursors such as Cu(II), Co(II), Mn(II), Bi(III), and Fe(III) salts or elemental Sn, in aqueous concentrated HX (X = Cl, Br, I) solutions, we obtained single crystals of the new 1-D pseudo-perovskite structures (4,4’-azpyH2)[Cu2Cl6], (4,4’-azpyH2)[MnCl2(H2O)2]Cl2, (4,4’-azpyH2)21[Cu2I4(I3)2](I2) (2,2’-hydpyH2)1[Cu2I4], (4,4’-hydpyH2)1[Cu2I4], and the 0-D pseudo-perovskite structure (4,4’-hydpyH2)[BiI6](I3), along with non-perovskite salt-like structures. Some structures contain protonated azopyridinium (azpyH22+) dications, obtained through protonation of the starting azopyridines, while others contain hydrazopyridinium (hydpyH22+) cations, produced in a reduction-protonation reaction. Starting from Cu(II) salts, we found the metal reduced to Cu(I) in the presence of iodide, but not for chloride. The azopyridine-containing structures are easily discriminated from hydrazopyridine derivatives by their negligible C–N–N–C torsion angles and unequivocal anti-conformations. The hydrazopyridine moieties showed C–N–N–C torsions ranging from 99 to 133° and the conformations around the hydrazo –HN–NH– moiety are best described as anti-clinal.

Graphical Abstract

Azo- and Hydrazo-Dipyridines in Halidometallate Structures