Two novel double-stranded dicopper(II) metallacyclophanes of formula (nBu(4)N)(4)[Cu-2(dpeba)(2)]center dot-4MeOh center dot 2Et(2)O have been (l) prepared by ynthe(nBu(4)N)(4)-[Cu-2(tpeba)(2)]center dot I2H(2) (2) of the rigid('rod-like') bridging ligands N,N'-4,4'-diphenylethynebis-(oxamate) (dpeba) and N,N'-1,4-diphenylenebts(oxamate) (tpeba), respectively. Single crystal X-ray, diffraction analysis of 1 confirms the presence of a dicopper(II)tetraaza[3.3]4,4'-diphenylethynophane metallacyclic structure featuring a very long intermetallic distance between the two square planar Cu-II ions = [r =14.95(1) angstrom]. The overall parallel-displaced pi-stacked conformation of the two nearly planar para substituted diphenyleth e s [dihedral angle (psi) of 7.8(1)degrees] leads to important deviations from the perpendicular orientation of the copper mean basal palnes with respect to the facing benzene planes [dihedral angles (phi) of 56.4(1) and 58.4(1)degrees]. X-band EPR spectra together with variable-temperature magnetic susceptibility and variable-field magnetization measurements of 1 and 2, both in solution and in the solid state; show the occurrence of a non-negligible, moderate to weak intramolecular antiferromagnet.ic coupling [-J = 3.9-4.1 (1) d 0.5-0.9 cm(-1) (2); H = -J S-1.S-2 with S-1 = S-2 S-Cu = 1/2]. Density functional calculations on the BS singlet (S = 0) an d triplet (S = 1) spin states of the model complexes 1 and 2 with an deal orthogonal molecular geometry (psi =0 degrees and phi = 90 degrees) support the occurrence of a spin polarization mec h amsm for the propagation of the exchange interaction between the two unpaired electrons occupying the d(xy) orbital of each square planar Cu-II ion through the predominantly pi-type orbital pathway of the double p-diphenylethyne (1) and di(phenylet.hynyl)phenylene spacers (2). Time-dependent density functional calculations reproduce the observed bathochromic shift of the main intrahgand (IL) pi-pi* transition in the electronic absorption spectra of 1 and 2 [lambda(1) = 308 (1) and 316 nm (2)]. In the series of orthogonal model complexes 1-5 With linear oligo(p-phenylene-ethynylene) (OPE) spacers, -C6H4(C CC6H4) (n = 1-5), a linear increase of the IL pi-pi* transition energy with the reciprocal of the intermetallic distance is theoretically predicted [v(max) = 1.99 X 10(4) + 2.15 X 10(5) (l/r) (S = 0) or upsilon = 2.01 X 10(4) + 2.18 X 10(5) (l/r) (S = 1)], which clearly indicates that the effective a-conjugation length increases with the number of phenylet.hyne repeating units. This is accompanied by an exponential decay of the antiferromagnetic coupling with the interinetallic distance [-J= 1.08 X 10(3) exp(-0.31r)], which supports the ability of the extended pi-conjugated OPEs to mediate the exchange interaction between the unpaired electrons of the two Cu-II centers with intermetallic distances in the range of 1.5-4.3 nm. Further developments may be then envisaged for this new family of oxamato-based dicopper(II) oligo-p-phenylethynophanes on the basis of the unique ligand capacity to act as a molecular antiferromagnetic wire.