Proton NMR Spectroscopy and Magnetic Properties of a Solution-Stable Dicopper(II) Complex Bearing a Single (mu)-Hydroxo Bridge

The reaction of copper(II) perchlorate with the macrocyclic ligand [22]py4pz in the presence of base leads to formation of a dinuclear complex [Cu2([22]py4pz)((mu)-OH)](ClO4)3·H2O, in which two copper ions are bridged by a single (mu)-hydroxo bridge. Each copper ion is further surrounded by four nitrogen atoms of the ligand. The (mu)-hydroxo bridge mediates a strong antiferromagnetic coupling (2J = -691(35) cm6^-1) between the metal centers, leading to relatively sharp and well-resolved resonances in the 1H NMR spectrum of the complex in solution. We herein report the crystal structure, the magnetic properties, and the full assignment of the hyperfine-shifted resonances in the NMR spectrum of the complex, as well as the determination of the exchange coupling constant in solution through temperature-dependent NMR studies.