Cobalt and nickel coordination polymers containing 3-pyridylnicotinamide and five-membered ring dicarboxylates

<div><p>Cobalt and nickel coordination polymers containing the conformationally flexible 3-pyridylnicotinamide (3-pna) ligand and a five-membered ring-based dicarboxylate ligand have been prepared and structurally characterized via single-crystal X-ray diffraction. [Co(tpdc)(3-pna)]_n (<b>1</b>) was prepared using 2,5-thiophenedicarboxylic acid (H₂tpdc). This material shows a 2-D layer structure containing {Co₂(OCO)₂} dimers linked by tpdc and 3-pna ligands. Compound <b>1</b> manifests an underlying 3,5-connected (4²6)(4²6⁷8) 3,5L2 topology. The isostructural pair of solids [Co(<i>D</i>-cam)(3-pna)(H₂O)₂]_n (<b>2</b>) and [Ni(<i>D</i>-cam)(3-pna)(H₂O)₂]_n (<b>3</b>) was obtained from the chiral <i>D</i>-camphorate (<i>D</i>-cam) ligand. These two materials possess acentric ribbon coordination polymer motifs. Compound <b>1</b> manifests antiferromagnetic coupling concomitant with Kramers doublet formation. Thermal properties of these materials are also discussed.</p></div

Structural Characterization of the [CuOR]2+ Core

Formal Cu(III) complexes bearing an oxygen-based auxiliary ligand ([CuOR]2+, R = H or CH2CF3) were stabilized by modulating the donor character of supporting ligand LY (LY = 4-Y, N,N′-bis(2,6-diisopropylphenyl)-2,6-pyridinedicarboxamide, Y = H or OMe) and/or the basicity of the auxiliary ligand, enabling the first characterization of these typically highly reactive cores by NMR spectroscopy and X-ray crystallography. Enhanced lifetimes in solution and slowed rates of PCET with a phenol substrate were observed. NMR spectra corroborate the S = 0 ground states of the complexes, and X-ray structures reveal shortened Cu–ligand bond distances that match well with theory