Structural, spectroscopic and magnetic properties of a novel copper(II) L-tyrosinato complex

The complex [Cu(L-Tyr)(2)(H2O)]center dot H2O (1) (L-Tyr = L-tyrosine) was obtained as crystals and characterized by Xray, spectroscopic (FT-IR, FT-Raman, NIR-vis-UV, and EPR) and magnetic methods. The monomeric complex crystallized in the monoclinic P2(1) symmetry with a = 11.967 (1) angstrom, b = 5.9986 (4) angstrom, c = 14.936 (1) angstrom. The amino N and carboxylate O atoms of chelating L-tyrosinate anions together with the O atom of water molecules create a slightly distorted square pyramidal environment around the Cu(II) ions (s = 0.11). The distance of about 5.998(1) angstrom [Cu(L-Tyr)(2)(H2O)] units is involved in a polymeric chain based on N(1)-H center dot center dot center dot O(4) vi and N(2)-H center dot center dot center dot O(5)(vi) hydrogen bonds. The d-d band found in the polycrystallinereflectance spectrum at 15 700 cm(-1) is composed of three B-2(1)(d(x2-y2)) -> (2)A(1) (d(z2)), B-2(1) -> B-2(2)(d(xy)) and B-2(1) -> E-2 (d(xz) approximate to d(yz)) transitions with energies 14 880, 15 800 and 19 950 cm(-1), respectively. In DMSO solution the complex preserves its square pyramidal geometry as evidenced by an intensive band at ca. 16 400 cm(-1). The EPR spectral parameters for powder (g(parallel to) = 2.236 and g(perpendicular to) = 2.063) and DMSO frozen solution (g(parallel to) = 2.250, g(perpendicular to) = 2.055, and A(parallel to) = 180 G) correspond to an axial symmetry of the Cu(II) coordination geometry with the d(x2-y2) orbital as a ground state of the unpaired electron. Furthermore, the frozen solution spectrum revealed signals corresponding to S = 1 spin states of Cu(II) ions coupled by dipole-dipole interactions with distinctly resolved hyperfine splitting due to two copper nuclei (vertical bar D vertical bar = 0.0468 cm(-1), g(parallel to) = 2.238, g(perpendicular to) = 2.06 and A(parallel to) = 85 G). The variable-temperature magnetic susceptibility measurements revealed the existence of a weak ferromagnetic interaction between neighboring copper(II) ions through the N-H center dot center dot center dot O hydrogen bonds.