Very Long-Distance Magnetic Coupling in a Dicopper(II) Metallacyclophane with Extended π-Conjugated Diphenylethyne Bridges

Self-assembly of the rigid rodlike ligand N,N′-4,4′-diphenylethynebis­(oxamate) (dpeba) and Cu2+ ions affords a novel dinuclear copper­(II) metallacyclophane (nBu4N)4[Cu2(dpeba)2]·4MeOH·2Et2O (1) featuring a very long intermetallic distance (r = 15.0 Å). Magnetic susceptibility measurements for 1 reveal a moderately weak but nonnegligible intramolecular antiferromagnetic coupling between the two metal centers across the double para-substituted diphenylethynediamidate bridge (J = −3.9 cm–1; H = –JS1S2, where S1 = S2 = SCu = 1/2). Density functional electronic structure calculations on 1 support the occurrence of a spin polarization mechanism.