TAILORED MAGNETIC-PROPERTIES IN TRINUCLEAR COPPER(II) COMPLEXES - SYNTHESIS, STRUCTURE, AND MAGNETIC-PROPERTIES OF COMPLEXES DERIVED FROM [1,3-PROPANEDIYLBIS(OXAMATO)]CUPRATE(II) ([CU(PBA)]2-)

Five new trinuclear Cu(II) complexes were synthesized: {[(tmen)Cu]2[mu-Cu(pba)]}(ClO4)2 (1), {[(pet)Cu]2[mu-Cu(pba)]}(ClO4)2.1/2H2O (2), {[(pmd)Cu]2[mu-Cu(pba)]}(BPh4)2.CH3CN (3), {[(bapa)CU]2[mu-Cu(pba)(H2O)]}(PF6)2 (4), and {[(terpy)Cu]2[mu-Cu(pba)]}(ClO4)2(5), where Cu(pba) = [1,3-propanediylbis(oxamato)]cuprate(II), tmen = N,N,N',N'-tetramethylethylenediamine, pet = N,N,N,N'',N''-pentaethyldiethylenetriamine, pmd = N,N,N',N'',N''-pentamethyldiethylenetriamine, bapa = bis(3-aminopropyl)amine, and terpy = 2,2':6',2''-terpyridine. The structures of 1-4 were determined by X-ray analysis. The crystals of 1 are orthorhombic, space group Pn2(1)a, with a = 26.529(3) angstrom, b = 14.077(2) angstrom, c = 8.330(1) angstrom, Z = 4, and R = 0.047 for 1804 reflections observed. The crystals of 2 are triclinic, space group P1BAR, with a = 20.070(6) angstrom, b = 17.430(5) angstrom, c = 15.334(4) angstrom, alpha = 91.06(2)-degrees, beta = 110.88(2)-degrees, gamma = 91.54(2)-degrees, Z = 4, and R = 0.108 for 3701 reflections observed. The crystals of 3 are monoclinic, space group P2(1)n, with a = 12.127(1) angstrom, b = 35.447(5) angstrom, c = 17.112(2) angstrom, beta = 95.72(1)-degrees, Z = 4, and R = 0.045 for 4879 reflections observed. The crystals of 4 are orthorhombic, space group Pbca, with a = 38.797(4) angstrom, b = 16.938(3) angstrom, c = 11.139(2) angstrom, Z = 8, and R = 0.059 for 1804 reflections observed. In 1 the three copper(II) ions are all approximately square-planar with almost coplanar basal planes. The central copper(II) ions of 2 and 4 are square-pyramidal, the apical positions being occupied by a perchlorate and a water oxygen, respectively. In 3 the central copper ion is square-planar. The terminal copper ions of compounds 2-4 are all pentacoordinated with geometries that are intermediate between square-pyramidal and trigonal-bipyramidal. If the coordination is described in terms of square-pyramidal geometry, the basal plane of each terminal copper is approximately perpendicular to the basal plane of the central copper ion. The distortion toward trigonal-bipyramidal geometry is largest for compound 2 and smallest for 4. Magnetic susceptibility and EPR measurements have been carried out for this series of complexes. The magnetic data have been interpreted using the Heisenberg Hamiltonian and lead to J values equal to -360, -170, -153, -110, and -80 cm-1 for 1-5, respectively. The intensity of the magnetic coupling is discussed in relation to the relative orientation of magnetic orbitals. The symmetry of EPR spectra is also discussed.