Influence of nitrogen-containing chelating ligands on the structures of zinc(II) 4,4'-ethylenedibenzoates.

The Zn(II) compounds, micro-4,4'-ethylenedibenzoato-bis[acetatoaqua(dipyrido[3,2-a:2',3'-c]phenazine)zinc(II)] dihydrate, [Zn(2)(C(2)H(3)O(2))(2)(C(16)H(10)O(4))(C(18)H(10)N(4))(2)(H(2)O)(2)] x 2H(2)O, (I), and catena-poly[[[aqua(pyrazino[2,3-f][1,10]phenanthroline)zinc(II)]-micro-4,4'-ethylenedibenzoato] N,N-dimethylformamide hemisolvate], {[Zn(C(16)H(10)O(4))(C(14)H(8)N(4))(H(2)O)] x 0.5C(3)H(7)NO}(n), (II), display very different structures because of the influence of the N-donor chelating ligands. In (I), the coordination geometry of each Zn(II) centre is distorted octahedral, involving two N atoms from one dipyrido[3,2-a:2',3'-c]phenazine (L1) ligand, and four O atoms from one bis-chelating acetate anion, one bridging 4,4'-ethylenedibenzoate (bpea) ligand and one water molecule. Adjacent Zn(II) atoms are bridged by one bpea ligand to form a dinuclear complex, and the dinuclear species is centrosymmetric. Two types of pi-pi interactions between neighbouring dinuclear species have been found: one is between the L1 ligands, and the second is between the L1 and bpea ligands. In this way, an interesting two-dimensional supramolecular layer is formed. The layers are further linked by O-H...O and O-H...N hydrogen bonds, generating a three-dimensional supramolecular network. In (II), each Zn(II) atom is square-pyramidally coordinated by two N atoms from one pyrazino[2,3-f][1,10]phenanthroline ligand, three O atoms from two different bpea ligands and one water molecule. The two bpea dianions are situated across inversion centres. The bpea dianions bridge neighbouring Zn(II) centres, giving a one-dimensional chain structure in the ab plane. As in (I), two types of pi-pi interactions between neighbouring chains complete a three-dimensional supramolecular structure. The results indicate that the structures of the N-donor chelating ligands are the dominant factors determining the final supramolecular structures of the two compounds.