The crystalline compounds (Hbipy) 2 [Ge(C 2 O 4 ) 3 ] (1) and (Hphen) 2 [Ge(C 2 O 4 ) 3 ]·2(H 2 O) (2) [Hbipy + is the 2,2′-bipyridinium cation (C 10 H 9 N 2 ), and Hphen + is the 1,10′-phenathrolinium cation (C 12 H 9 N 2 )] 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(C 2 O 4 ) 3 ] 2− , which co-crystallises with Hbipy + (in 1), or Hphen + and water molecules (in 2). In 1, the germanium oxalate anionic complex, [Ge(C 2 O 4 ) 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.