Tetra­kis(2,2′-bipyrid­ine)di-μ(3)-hydroxido-bis(μ-2-oxidobenzoato)tetra­copper(II) dinitrate tetra­hydrate

The tetra­nuclear title complex, [Cu(4)(C(7)H(4)O(3))(2)(OH)(2)(C(10)H(8)N(2))(4)](NO(3))(2)·4H(2)O, has a crystallographically imposed centre of symmetry. The Cu(II) atoms display a distorted square-pyramidal coordination geometry and are linked by two μ(2)-phenolate O atoms from the salicylate ligands and two μ(3)-hydroxo groups, forming a Cu(4)O(4) core that adopts a ‘stepped-cubane’ geometry. In the crystal, the cations are linked by O—H⋯O hydrogen bonds to the nitrate anions, which are in turn connected via O—H⋯O inter­actions to centrosymmentric water tetra­mers.