Construction of N,N′-di(3-pyridyl)adipoamide-based Zn(ii) and Cd(ii) coordination networks by tuning the isomeric effect of polycarboxylate ligands

Abstract

Eight new Zn(II) and Cd(II) coordination networks containing N,N′-di(3-pyridyl)adipoamide (L) and polycarboxylate ligands, {[Zn₂(2,5-PDC)₂(L)(H₂O)₂]·2H₂O}_∞ (H₂PDC = 2,5-pyridinedicarboxylic acid), 1, [Zn₂(2,6-PDC)₂(L)]_∞, 2, {[Zn₂(3,4-PDC)₂(L)(H₂O)₆]·4H₂O}_∞, 3, {[Cd(2,6-PDC)(L)(H₂O)]·4H₂O}_∞, 4, [Zn(1,3,5-HBTC)()]_∞ (H₃BTC = benzenetricarboxylic acid), 5, {[Cd(1,2,3-HBTC)(L)(H₂O)]·H₂O}_∞, 6, {[Cd₂(1,3,5-HBTC)₂(L)(H₂O)₂]·2H₂O}_∞, 7, and {[Zn₃(1,2,4-BTC)₂(L)(H₂O)₄]·4H₂O}_∞, 8, have been synthesized by hydrothermal reactions and characterized by single crystal X-ray crystallography. Structural analysis reveals that 1 and 2 form pleated hcb layers with 1D helical chains, in which the layers of 1 interdigitate with each other and those of 2 are linked by the π–π stacking interactions. Complexes 3 and 4 exhibit 1D ladders with single and double rungs, respectively, whereas 5 shows a 2D pleated net with the sql topology, 6 displays a 3D dia coordination network and 7 forms a 2D structure with the (6³)(6⁶)-3,4L88 topology. The BTC³⁻ ligands in 8 adopt the μ₄-bonding modes, resulting in a 3D coordination network with the rare (6⁵·8)-hxg-d-4-P2/c topology. The various bonding modes, the ligand-isomerism of the polycarboxylate ligands and the identity of the metal center play important roles in determining the structural diversity. Their thermal and luminescent properties are also discussed.