Tris(piperazinediium) bis-[tris-(pyridine-2,6-dicarboxyl-ato)neodymate(III)] 15.33-hydrate.

The title compound, (C(4)H(12)N(2))(3)[Nd(C(7)H(3)NO(4))(3)](2)·15.33H(2)O or (pipzH(2))(3)[Nd(pydc)(3)](2)·15.33H(2)O (in which pipz is piperazine and pydcH(2) is pyridine-2,6-dicarboxylic acid), was synthesized by the reaction of NdCl(3)·6H(2)O with the proton-transfer compound (pipzH(2))(pydc) in aqueous solution. The nine donor atoms of the three pydc(2-) ligands form a distorted tricapped trigonal-prismatic arrangement around the Nd(III) center. Considerable C-O⋯π stacking inter-actions between CO groups of carboxyl-ate fragments and aromatic rings of pydc(2-) with distances of 3.135†(5)-3.255†(5)†à are observed. In the crystal structure, a wide range of hydrogen-bonding [of the types O-H⋯O, N-H⋯O and C-H⋯O, with D⋯A distances ranging from 2.608†(10) to 3.278†(7)†à ], ion-pairing and C-O⋯π stacking interactions connect the various components into a supra-molecular structure. There is a high degree of solvent disorder in the structure; the occupancies of five water molecules refined to 0.6, 0.5, 0.4, 0.25 and 0.25.