Three new pyridine-2,6-dicarboxylate copper(II) compounds with coordinated pyridine-based ligands: Synthesis, characterisation and crystal structures

摘要

Three new Cu(II) compounds of pyridine-2,6-dicarboxylic acid (H _2pdc) with meta-substituted pyridines as additional ligands have been synthesized and structurally characterised using X-ray diffraction. Two of them are mononuclear compounds, i.e. [Cu(pdc)(3acpyr)(H_2O) (1) (3acpyr = 3-acetylpyridine) and [Cu(pdc)(3HOp)(H_2O)(H_2O)_2 (2) (3HOp = 3-hydroxypyridine). The third compound is polynuclear, i.e. [Cu(pdc)(μ-3HOmp-κN,O)_n (3) (3HOmp = 3-(hydroxymethyl) pyridine). The three compounds are also characterised by IR, EPR and ligand field spectroscopy. The geometry around the Cu(II) ions is distorted square pyramidal for compounds 1 and 2 and distorted octahedral for compound 3. The lattice of compound 1 is organised by an intra-sheet hydrogen-bond pattern generating double layers. Compound 2 has a lattice arranged by the two water molecules in the lattice with complicated 2D O-H?O intra-sheet hydrogen bonding motifs. The zig-zag chains in compound 3 are further organised in layers, due to the axial coordination at Cu(II), forming a so-called (4, 3) ladder-like one-dimensional coordination polymer. These ladders are interconnected by hydrogen bonding.