Long-Range Magnetic Coupling through Extended π-Conjugated Aromatic Bridges in Dinuclear Copper(II) Metallacyclophanes

Self-assembly of 1,4-phenylenebis(oxamate) and 4,4‘-biphenylenebis(oxamate) ligands and Cu2+ ions gives two new dinuclear copper(II) metallacyclophanes where the two metal centers are connected by double para-substituted aromatic diamide bridges. Despite the relatively large intramolecular Cu−Cu distance of ca. 8 and 12 Å for each complex, magnetic susceptibility measurements evidence strong to moderately strong intramolecular antiferromagnetic couplings (−J values of the order of 100 and 10 cm-1, respectively). Density functional theory calculations on these compounds and their homologues with linear oligo-p-phenylenediamide bridges predict a rather slow exponential decay of magnetic coupling with increasing intermetal distance (r values up to 25 Å) along this novel series of dicopper metalla-amidocyclophanes.