Binuclear and chain-structure zinc(II) complexes constructed from 3,4-dimethoxy-trans-cinnamic acid and N-donor coligands 4-(1H-pyrazol-3-yl)pyridine and 4,4'-bipyridine.

3,4-Dimethoxy-trans-cinnamic acid (Dmca) reacts with zinc sulfate in the presence of 4-(1H-pyrazol-3-yl)pyridine (L1) or 4,4'-bipyridine (L2) under hydrothermal conditions to afford two mixed-ligand coordination complexes, namely tetrakis(μ-3,4-dimethoxy-trans-cinnamato-κ(2)O:O')bis[[4-(1H-pyrazol-3-yl)pyridine]zinc(II)] heptahydrate, [Zn2(C11H11O4)4(C8H7N3)2]·7H2O or [Zn2(Dmca)4(L1)2]·7H2O, (I), and catena-poly[[bis(3,4-dimethoxy-trans-cinnamato-κO)zinc(II)]-μ-4,4'-bipyridine-κ(2)N:N'], [Zn(C11H11O4)2(C10H8N2)]n or [Zn(Dmca)2(L2)]n, (II). The Zn(II) centres in the two compounds display different coordination polyhedra. In complex (I), the Zn(II) cation is five-coordinated with a pseudo-square-pyramidal geometry, while in complex (II) the Zn(II) cation sits on a twofold axis and adopts a distorted tetrahedral coordination environment. Complex (I) features a centrosymmetric binuclear paddle-wheel-like structure, while complex (II) shows a chain structure. This study emphasizes the significant effect of the coordination mode of both carboxylate-group and N-donor coligands on the formation of complex structures.