The chain structure of [Ni(C(4)H(2)O(4))(C(12)H(8)N(2))(H(2)O)](n) with different types of fumarate bridging.

Using modified solvothermal conditions (longer cooling time), beside previously characterized dark-green crystals of [Ni(C(4)H(2)O(4))(C(12)H(8)N(2))] (main product), a few light-green crystals of the polymeric title compound, catena-poly[[aqua-(1,10-phenanthroline-κ(2)N,N')nickel(II)]-μ-fumarato-κ(2)O:O'-[aqua-(1,10-phenanthroline-κ(2)N,N')nickel(II)]-μ-fumarato-κ(4)O,O':O'',O'''], [Ni(C(4)H(2)O(4))(C(12)H(8)N(2))(H(2)O)](n) were isolated. Its crystal structure is made up from zigzag chains, propagating in [001], in which the Ni(2+) ions are linked alternatively by μ(2)-fumarato and bis-chelating fumarato bridging ligands. The Ni(2+) ion is coordinated in a deformed octa-hedral geometry by one chelating 1,10-phenanthroline ligand, one aqua ligand in a cis position with regard to both N-donor atoms and by two different fumarato ligands, each residing with its central C=C bond on an inversion centre, occupying the remaining coordination sites in a fac fashion. The chains thus formed are linked by O-H⋯O hydrogen bonds and π-π inter-actions between the aromatic rings of the phenanthroline ligands with a shortest ring centroid separation of 3.4787 (10) Å.