Poly[bis-(μ-2-amino-4-nitro-benzoato)di-μ-aqua-dirubidium]

In the structure of the title salt, [Rb2(C7H5N2O4)2(H2O)2] n , the asymmetric unit comprises two independent and different seven-coordinate Rb(+) cations, one forming an RbO7 polyhedron, the other a RbO6N polyhedron, each of which is considerably distorted. The RbO7 polyhedron comprises bridging O-atom donors from two water mol-ecules, three carboxyl-ate groups, and two nitro groups. The RbO6N polyhedron comprises the two bridging water mol-ecules, one monodentate amine N-atom donor, one carboxyl O-atom donor and three O-atom donors from nitro groups (one from the chelate bridge). The extension of the dinuclear unit gives a three-dimensional polymeric structure which is stabilized by both intra- and inter-molecular amine N-H⋯O and water O-H⋯O hydrogen bonds to carboxyl and water O-atom acceptors, as well as a number of inter-ring π-π inter-actions [minimum centroid-centroid separation = 3.364 (2) Å]. The title salt is isostructural with the analogous caesium salt.