Supramolecular salts containing the anionic [Ge(C2O4)3]2− complex and heteroaromatic amines

The crystalline compounds (Hbipy)2[Ge(C2O4)3] (1) and (Hphen)2[Ge(C2O4)3] · 2(H2O) (2) [Hbipy+ is the 2,2′-bipyridinium cation (C10H9N2), and Hphen+ is the 1,10′-phenathrolinium cation (C12H9N2)] were isolated from mild hydrothermal syntheses and their structures were elucidated from single-crystal X-ray diffraction. The two compounds were further characterised by vibrational spectroscopy (FT-IR and FT-Raman), thermogravimetric analysis (TGA) and CHN elemental composition. Compounds 1 and 2 comprise the tris(oxalato-O,O′)germanate dianion complex, [Ge(C2O4)3]2−, which co-crystallises with Hbipy+ (in 1), or Hphen+ and water molecules (in 2). In 1, the germanium oxalate anionic complex, [Ge(C2O4)3]2−, and the Hbipy+ organic residues interact mutually via N–H⋯O hydrogen bonding interactions, leading to supramolecular discrete hydrogen-bonded units which are further interconnected via π–π stacking. Compound 2, on the other hand, exhibits a more complex hydrogen bonding network due to the presence of the water molecules of crystallisation which, along with π–π stacking between neighbouring Hphen+ residues, mediate the crystal packing.