Self-assembled Zn(II) coordination complexes based on mixed V-shaped asymmetric multicarboxylate and N-donor ligands

摘要

Hydrothermal reaction between Zn(OAc)_2·2H_2O and three asymmetric semirigid V-shaped multicarboxylate ligands H_ 3L~(1-3) 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·(H_ 2O)_(2n) (1), [Zn_3(L~2)_ 2(4,4′-bpy)(H_2O)_2]_n· (H_2O)_(2n) (2), [Zn_3(L~3)_ 2(4,4′-bpy)_2(H_2O)_4]_ n·(H_2O)_(6n) (3), [Zn_3(L~ 1)_2(bix)_3]_n·(H_ 2O)_(7n) (4), [Zn_3(L~2)_ 2(bix)_3]_n·(H_2O)_(4n) (5), and [Zn_3(HL~3)_2(bix)_2]_ n (6), where H_3L~1, H_3L~2, H_3L~3 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.