Structural library of coordination polymers based on flexible linkers exploiting the role of linker coordination angle: synthesis, structural characterization and magnetic properties

Abstract

Herein we report six new coordination polymers [Co(1,2-pda)(1,2-bix)]_n (1a), [Co(hfipbb)(1,2-bix)]_n·nH₂O (2a), [Co(ADA)(1,2-bix)]_n (3a), [Co(ADA)(1,3-bix)]_n·nH₂O (3b), [Co(1,4-pda)₂(2-pztz)]₂[Co(H₂O)₆]·2nH₂O (4a), [Co₂(μ-OH)(1,3-pda)(4-ptz)]_n (4b) based on the flexible carboxylate ligands 1,2-phenylenediaceticacid (1,2-H₂pda), 1,3-phenylenediaceticacid (1,3-H₂pda), 1,3-adamantanediacetic acid (H₂ADA), 4,4′-(hexa-fluoroisopropylidene)bis(benzoicacid) (H₂hfipbb) and secondary N-donor ligands 1,3-bis(imidazole-1-ylmethyl)-benzene (1,3-bix), 1,2-bis(imidazole-1-ylmethyl)-benzene (1,2-bix), 5-(4-pyridyl) tetrazole (4-ptz) and 2-(2H-tetrazol-5-yl)pyrazine (2-pztz). All the compounds were characterized by single crystal X-ray diffraction analysis, IR spectroscopy, elemental analysis and bulk homogeneity by powder X-ray diffraction. A subtle relation between the position of the coordinating groups in the linker (known as linker coordination angle, LCA) and the dimensionality and topology of the final architectures of the title compounds has been discussed systematically by comparing with the structurally related reported compounds [Co(1,4-pda)(1,4-bix)]_n (1b), [Co(hfipbb)(1,4-bix)_0.5]_n (2b) and [Co₂ (μ-OH)(1,4-pda)(4-ptz) ]_n·nH₂O (4c). The compounds studied in the present work are classified into four different mixed linker classes, based on the skeleton geometry of the linker. Finally, temperature dependent magnetic susceptibility measurements have been studied and the relevant zero-field splitting parameters have been determined.