Influence of Metal Ions on the Structural Complexity of Mixed-Ligand Divalent Coordination Polymers

Abstract

The reactions of the angular ligand 4,4′-oxybis(N-(pyridin-3-yl)benzamide) (L1) and 1,4-naphthalenedicarboxylic acid (1,4-H2NDC) with divalent metal salts yielded three distinct coordination polymers (CPs): {[Zn2(L1)(1,4-NDC)2]·MeOH}n, 1, {[Cu(L1)(1,4-NDC)(H2O)]·3H2O}n, 2, and {[Cd(L1)(1,4-NDC)]·2H2O}n, 3. Complex 1 features a 2-fold interpenetrated 3D framework with the (412·63)-pcu topology, while complex 2 reveals a 1D triple-strained helical chain and complex 3 displays a 3-fold interpenetrated 3D framework with (66)-dia topology. Additionally, the reactions of the flexible ligand N,N′-bis(3-methylpyridyl) adipoamide (L2) afforded {[Co4(L2)0.5(1,4-NDC)3(H2O)3(µ3-OH)2]·EtOH·2H2O}n, 4, {[Zn2(L2)(1,4-NDC)2]·2CH3OH}n, 5, and [Cd(L2)(adipic)(H2O)]n (H2adipic = adipic acid), 6, exhibiting a self-catenated 3D framework with the (420·68)-8T32 topology, a 2D layer with the (413·62) − (4,4)IIb topology, and a 2D layer with the (44·62)-sql topology, respectively. The structural diversity observed in complexes 1–6 highlights the pivotal influence of the metal center on the degree of entanglement in CPs within mixed-ligand systems. The thermal stability and luminescent properties of complexes 1–3, 4, and 6 are also discussed.

Keywords

• coordination polymers
• crystal structure
• entanglement
• dicarboxylic acid
• bis-pyridyl-bis-amide