MAGNETO-STRUCTURAL CORRELATION IN (μ-ALKOXO/HYDROXOXμ-CARBOXYLATO)-DICOPPER(II) SYSTEMS: SYNTHESIS, X-RAY STRUCTURE AND MAGNETIC PROPERTIES OF AQUO(μ-HYDROXO) (μ-ARYLCARBOXYLATO)BIS(N,N,N',N'-TETRAMETHYLETHANE-l,2-DIAMINE)DICOPPER(II)DIPERCHLORATE

Abstract

Asymmetrically dibridged dicopper(II) complexes, [Cu2(OH)(O2CC6H4-P-Me)(tmen)2(H2O)]-(C104)2 (1) and [Cu2(OH)(O2CC6H4-P-OMe)(tmen)2(H2O)](C1O4)2 (2) (tmen = N,N,N',N'-tetramethylethane-l,2-diamine), were prepared and structurally characterized. Complex 1 crystallizes in the monoclinic space group P21/a with a= 17.718(2), b = 9.869(1), c= 19.677(2)Å, β= 115.16(1)°, V = 3114.3(6)Å3 and Z = 4. The structure was refined to R(wR2) = 0.067(0.178). Complex 2 crystallizes in the monoclinic space group P21/a with a = 17.695(3), b = 9.574(4), c = 20.104(2)Å, (β= 114.18(1)°, V=3107(1)Å3 and Z = 4. The final residuals are R(wR2) = 0.067(0.182). The complexes have a [Cu2(μ-OH)(μ-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) Å, 124.4(2)° for 1 and 3.374(1) Å, 123.3(3)° for 2. The complexes show axial X-band EPR spectral features in methanol glass at 77 K giving g⊥ = 2.02, g|| = 2.3(,A|| = 165 × 10-4cm-1) and a visible band near ∼ 630 nm in methanol. The complexes are weakly antiferromagnetic. A theoretical fit of the magnetic susceptibility data in the temperature range 40–295K gives J = 10cm-1, g = 2.05 for 1 and - J = 10cm-1, g = 2.0 for 2. Plots of - 2J versus the Cu-OH-Cu angle (ø) in this class of asymmetrically dibridged dicopper(II) complexes having dX2Y2 dX2_y2 magnetic orbitals show a linear magneto-structural correlation: - 2J(cm-1)= 11.48ø(deg) 1373.