Synthesis, solid state and solution structures of two isomeric dicopper(II) complexes with functionalized azetidine ligands

Reported are the crystal and solution structures (determined by X-ray crystallography and EPR spectroscopy/simulation of the EPR spectra, respectively) of two dinuclear Cu^II complexes, coordinated to isomeric dinucleating azetidine-based ligands, whose N₃ cavities (pyridine/azetidine/secondary amine) are bridged by para- or meta-substituted phenyl groups. The Cu^II sites in the two dinuclear systems are similar to each other and as expected from the known structure of the corresponding mononuclear complex. The significant differences between the crystal structures of the mono- and the two dinuclear complexes and between the crystal and the solution structures are due to the elasticity of the Cu^II coordination sphere, the flexibility of the dinucleating ligands and subtle changes related to weak interactions (crystal lattice, solvation, anion coordination/ion pairing).