Magneto-structural correlation in (mu-alkoxo/hydroxo)(mu-carboxylato)dicopper(II) systems: Synthesis, X-ray structure and magnetic properties of aquo(mu-hydroxo) (mu-arylcarboxylato)bis(N,N,N ',N '-tetramethylethane-1,2-diamine)dicopper(II) diperchlorate

Asymmetrically dibridged dicopper(II) complexes, [Cu-2(OH)(O2CC6H4-p-Me)(tm en)(2)(H2O)](ClO4)(2) (1) and [Cu-2(OH)(O2CC6H4-p-OMe)(tmen)(2)(H2O)](ClO4) (2) (2) (tmen = N,N,N',N'-tetramethylethane-1,2-diamine), were prepared and structurally characterized. Complex 1 crystallizes in the monoclinic space group P2(1)/a with a = 17.718(2), b = 9.869(1), c = 19.677(2) Angstrom, be ta = 115.16(1)degrees, V = 3114.3(6) Angstrom(3) and Z = 4. The structure w as refined to R(wR(2)) = 0.067(0.178). Complex 2 crystallizes in the monocl inic space group P2(1)/a with a = 17.695(3), b = 9.574(4), c = 20.104(2) An gstrom, beta = 114.18(1)degrees, V = 3107(1) Angstrom(3) and Z = 4. The fin al residuals are R(wR(2)) = 0.067(0.182). The complexes have a [Cu-2(mu-OH) (mu-OH)(mu-O2CAr)](2+) core with tmen Ligands occupying the terminal sites of the core. In addition, one copper is axially bound to a water molecule. The Cu ... Cu distances and the Cu-OH Cu angles in the core are 3.394(1) An gstrom, 124.4(2)degrees for 1 and 3.374(1) Angstrom, 123.3(3)degrees for 2. The complexes show axial X-band EPR spectral features in methanol glass at 77 K giving g(perpendicular to) = 2.02, g(parallel to) = 2.3 (A(parallel t o) = 165 x 10(-4) cm(-1)) and a visible band near similar to 630 nm in meth anol. The complexes are weakly antiferromagnetic. A theoretical fit of the magnetic susceptibility data in the temperature range 40-295 K gives -J = 1 0 cm(-1), g = 2.05 for 1 and -J = 10 cm(-1), g = 2.0 for 2. Plots of -2J ve rsus the Cu-OH-Cu angle (phi) in this class of asymmetrically dibridged dic opper(II) complexes having d(x2-y2)-d(x2-y2) magnetic orbitals show a linea r magneto-structural correlation: -2J(cm(-1)) = 11.48 phi(deg) - 1373.