A series of metal–organic frameworks constructed with 2,2′-bipyridine-3,3′-dicarboxylate: Syntheses, structures, and physical properties

To determine the influence of metal ion and the auxiliary ligand on the formation of metal–organic frameworks, six new coordination polymers, {[Mn2(bpdc)(bpy)3(H2O)2] · 2ClO4 · H2O}n (1), {[Mn(bpdc)(dpe)] · CH3OH · 2H2O}n (2), {[Cu(bpdc)(H2O)2]}n (3), {[Zn(bpdc)(H2O)2]}n (4), {[Cd(bpdc)(H2O)3] · 2H2O}n (5), and {[Co(bpdc)(H2O)3] · 0.5dpe · H2O}n (6) (H2bpdc = 2,2′-bipyridine-3,3′-dicarboxylic acid, bpy = 2,2′-bipyridine, dpe = 1,2-di(4-pyridyl) ethylene), have been synthesized and characterized. Compound 1 forms 1D helical chain structure containing two unique MnII ions. In 2, the bridging ligand dpe links Mn-bpdc double zigzag chains to generate a layer possesses rectangular cavities. In 3, bpdc2− ligand connects to three metal centers forming a 2D network. Different from the above compounds, 4 displays a 1D double-wavelike chain. Compound 5 features a helical chain. Compound 6 also displays a helical chain with guest molecule dpe existing in the structure. These diverse structures illustrate rational adjustment of metal ions and the second ligand is a good method for the further design of helical compounds with novel structures and properties. In addition, the magnetic properties of 2, 3 and 6, the thermal stabilities and photoluminescence properties of 4 and 5 were also studied.