Synthesis, crystal structure, weak antiferromagnetic behavior and electronic studies of novel [((−)-sparteine)(PhCO 2)(Cl)]Cu(II) complex

Abstract

[((−)-Sparteine)(PhCO 2)(Cl)]Cu(II) 1 complex is obtained by direct synthesis using copper(0). 1 crystallizes in the monoclinic space group P2 1 with a=14.7355(12), b=8.9768(5), c=17.2810(10) A ̊ , β=111.916(5)°, and Z=4. The electronic spectrum of 1 shows a broad band with λ max ∼841 nm (ε=0.261 mM −1 cm −6) characteristic of a low symmetry and tetragonally distorted square pyramidal local Cu geometry. The far IR spectrum of 1 shows characteristic vibrations of Cu–Cl (260, 267 cm −1), Cu–N (436, 467 cm −1) and Cu–O (457 cm −1) bonds. The 1H NMR spectrum of 1 is typical of magnetic Cu(II) complexes with line broadening due to efficient nuclear relaxation from the metal center. ESR spectra of polycrystalline 1 at 77 K show an axial spectrum with linewidth of 58.6 G and at 300 K of 89.0 G, with areas in the ratio A 77/ A 300=2.79, indicative of antiferromagnetic order. The linewidth is reduced by 34% on going from 300 to 77 K. Standard magnetization measurements at low temperatures show an Curie–Weiss behavior with θ=−21.67 K, suggesting a weak exchange coupling interaction. The crystalline structure of 1 shows that the lattice is arranged so that the space between molecules is smaller than 40 Å 3, not enough to accommodate solvent molecules. However, the shortest Cu–Cu contact is 7.5912(8) Å.