Self-Assembled Zn(II) Coordination Complexes Based on Mixed V-Shaped Asymmetric Multicarboxylate and N-Donor Ligands

Hydrothermal reaction between Zn(OAc)(2)center dot 2H(2)O and three asymmetric semirigid V-shaped multicarboxylate ligands H3L1-3 with the help of a 4,4'-bipyridine (4,4'-bpy) or 1,4-bis(imidazol-1-ylmethyl)benzene (bix) linker led to the isolation of six new coordination polymers, including [Zn-3(L-1)(2)(4,4'-bpy)(2)](n)center dot(H2O)(2n) (1), [Zn-3(L-2)(2)-(4,4'-bpy)(H2O)(n)center dot(H2O)(2n) (2), [Zn-3(L-3)(2)(4,4'-bpy)(2)(H2O)(4)](n)center dot(H2O)(6n) (3), [Zn-3(L-1)(2)-(bix)(3)](n)center dot(H2O)(7n) (4), [Zn-3(L-2)(2)(bix)(3)](n)center dot(H2O)(4n) (5), and [Zn-3(HL3)(2)(bix)(2)](n) (6), where H3L1, H3L2, H3L3 ligands represent 3-(2-carboxyphenoxy)phthalic acid, 4-(2-carboxyphenoxy)phthalic acid, 3-(4-carboxyphenoxy)phthalic acid, respectively. Single crystal X-ray diffraction analysis reveals a three-dimensional (3D) network for 1 and 3-5 but a two-dimensional (2D) structure for 2 and 6. Despite the construction from the polymetallic chains connected by the 4,4'-bpy ligands for both compounds 1 and 2, a 3D architecture was revealed for the former species while a 2D configuration for the latter one. Complex 3 contains open nanotube building units composed of sole 44-numbered metallomacrocycles. For 4, the 20-numbered metallomacrocycle subunits linked by Zn ions give a 1D chain, which further form a 3D polymeric structure with the help of the other cyclic-shaped subunits made from the bix ligands and Zn ions. A 3D framework of 5 is generated from the 2D sheets simplified as a (6,3) net bound by the bix ligands. Compound 6 shows a 2D corrugated framework simplified as a (4,4) net assembled by the bix ligand and dinuclear zinc unit as node. These results seem to suggest that the diversity in the building subunits formed in 1-6 actually originates from the intrinsic nature of the three asymmetric V-shaped tricarboxylate ligands together with the tunable coordination geometry and molecular configurations of ligands by the N-donor ligand employed. In addition, the thermal stability and luminescence properties for the series of six complexes have also been investigated.