1,1'-Methylenedipyridinium tetrachloridocuprate(II) and bis[tetrachloridoaurate(III)] hybrid salts by X-ray powder diffraction.

In order to explore the potential propensity of the 1,1'-methylenedipyridinium dication to form organic-inorganic hybrid ionic compounds by reaction with the appropriate halide metal salt, the organic-inorganic hybrid salts 1,1'-methylenedipyridinium tetrachloridocuprate(II), (C(11)H(12)N(2))[CuCl(4)], (I), and 1,1'-methylenedipyridinium bis[tetrachloridoaurate(III)], (C(11)H(12)N(2))AuCl(4), (II), were obtained by treatment of 1,1'-methylenedipyridinium dichloride with CuCl(2) and Na[AuCl(4)], respectively. Both hybrid salts were isolated as pure compounds, fully characterized by multinuclear NMR spectroscopy and their molecular structures confirmed by powder X-ray diffraction studies. The crystal structures consist of discrete 1,1'-methylenedipyridinium dications and CuCl(4) and AuCl(4) anions for (I) and (II), respectively. As expected, the dications form a butterfly shape; the Cu(II) centre of CuCl(4) has a distorted tetrahedral configuration and the Au(III) centre of AuCl(4) shows a square-planar coordination. The ionic species of (I) and the dication of (II) each have twofold axial symmetry, while the two AuCl(4) anions are located on a mirror-plane site. Both crystal structures are stabilized by intermolecular C-H···Cl hydrogen bonds and also by Cl···π interactions. It is noteworthy that, while the average intermolecular centroid-centroid pyridinium ring distance in (I) is 3.643 (8) Å, giving strong evidence for noncovalent π-π ring interactions, for (II), the shortest centroid-centroid distance between pyridinium rings of 5.502 (9) Å is too long for any significant π-π ring interactions, which might be due to the bulk of the two AuCl(4) anions.