Crystal engineering through charge-assisted hydrogen bonds, multiple C–H⋯O bonds and π–π stacking: from (H2bipy)[Cu(ox)2] to (H2bipy)[NaH(ox)2] and (H2bipy)[H2(ox)2] (H2bipy = 4,4′-bipyridin-1,1′-dium; ox = oxalate)

The title compounds were assembled through charge-assisted hydrogen bonds, multiple C–H⋯O bonds and π–π stacking, and structurally characterized. The compounds, with dramatic differences in the cations of their tectons, are isostructural and featured 1D ribbons of alternating anions and cations. The 1D ribbons are aligned edge-to-edge to generate 2D sheets through arrays of C–H⋯O bonds. The 2D sheets then stack directly upon each other, resulting in alternating homogeneous columns of bipyridinium cations and oxalate anions in the structure.