2,2′-{1,1′-[2,2′-Oxalylbis(hydrazin-2-yl-1-yl-idene)] diethyl-idyne}dipyridinium bis-(perchlorate) dihydrate

Abstract

The title salt, C16H18N6O22+·2ClO4 -·2H2O, was obtained unintentionally as a major product in the reaction of Zn(ClO4) 2·6H2O with the N',N'2-bis-[(1E)-1-(2- pyrid-yl)ethyl-idene]ethanedihydrazide (H2 L) ligand. The (H4 L)2+ cation lies across a centre of inversion. The pyridiniumimine fragments of (H4 L)2+ adopt syn orientations. Intra-molecular N - H⋯N and N - H⋯O hydrogen bonds lead to the formation of S(5) motifs. In the crystal, neighbouring cations are connected by π-π inter-actions between pyridinium units with a centroid-centroid distance of 3.600 (1) Å. Moreover, the crystal components are assembled into two-dimensional layers via N - H⋯O and O - H⋯O hydrogen bonds, with no direct hydrogen-bonding inter-actions between cations.