Synthesis and characterisation of new coordination polymers by combining 2-pyridyl oximes or alcohols with functionalised terephthalic acid analogues

Abstract

Isolation of mixed-ligand compounds has attracted considerable research interest as the synergy between ligands results in species with interesting technological, environmental and biomedical applications. In this study, initial employment of 2-pyridyl oximes or 2-pyridyl alcohols in combination with 2-hydroxyterephthalic acid (H₃MHBDC) and 2,5-dihydroxyterephthalic acid (H₄DHBDC) has yielded a new family of 1D coordination polymers and a metal cluster, namely [M(H₂pyaox)₂(H₂DHBDC)]_n (M = Zn, 1; Mn, 2), [Co₃(mpko)₄(Hmpko)₂](H₂DHBDC)₂·2DMF (3·2DMF), [M(Hhmp)₂(H₂DHBDC)]_n·DMF (M = Ni, 4·DMF; Zn, 5·DMF), [Ni(H₂pyaox)₂(HMHBDC)]_n·2DMF (6·2DMF), and [Zn(Hmpko)₂(HMHBDC)]_n·DMF (7·DMF), where H₂pyaox = pyridine-2-amidoxime and Hmpko = 2-methyl pyridyl ketoxime. 1–7 are the first compounds bearing a 2-pyridyl oxime or 2-pyridinemethanol (Hhmp) with H₃MHBDC or H₄DHBDC in their neutral or anionic form. Notably, 4 exhibits a high capacity for Co²⁺ uptake (900 mg Co²⁺ g⁻¹4), which can be attributed to the presence of free coordination sites in the carboxylate linker.