In anhydrous rubidium rhodizonate , the rhodizonate anions are stacked in parallel columns, as are the rubidium ions. In the plane perpendicular to the columns, these are arranged as two interleaved hexagonal grids. The anions are planar.
Anhydrous potassium rhodizonate  has a distinct but similar structure. The anions and cations are arranged in alternate planes. Within each plane, the anions are arranged in a hexagonal grid. Each potassium ion is arranged so that it connects symmetrically to eight oxygens of four anions, two from each adjacent plane. The anions are slightly twisted in the "boat" shape (with 0.108 Å of rms deviation from mean plane). Sodium rhodizonate  has the same structure, with slightly more distorted anions (0.113 Å rms)
In solution, the rhodizonate anion is not hydrated.