[{Cu(phen)2}(μ-malato){Cu(phen)(NO3)}](NO3)⋅4H2O: malate acting as a tetradentate and dibridging ligand in a dinuclear copper complex.

The crystal structure of the title compound, μ-2-hydroxy­butane­dioato-1κ2 O4, O4′:2κ3 O1, O2, O4-nitrato-2κ O-tris­(1,10-phen­anthroline)-1κ4 N, N′;2κ2 N, N′-dicopper(II) nitrate tetra­hydrate, [Cu2(C4H3O5)(NO3)(C12H8N2)3](NO3)·4H2O, contains an unsymmetrical dinuclear copper complex with Cu(phen)2 and Cu(phen)(NO3) moieties (phen is 1,10-phenanthroline) bridged by a malate (2-hydroxy­butane­dioate) ligand, which acts as a double-bridging and tetra­dentate ligand. As a result of this double-bridging action, especially the direct coordination of the O atom of one carboxyl­ate group of malate to the two Cu atoms, the Cu⋯Cu distance is only 4.199 (1) Å and the two phen planes are roughly parallel [the shortest inter­planar distance is 3.28 (1) Å], exhibiting an obvious intra­molecular π–π stacking inter­action. [ABSTRACT FROM AUTHOR]