Structural, spectroscopic and magnetic properties of a novel copper(ii) l-tyrosinato complex?

RSC Advances Pub Date: 2014-11-07 DOI: 10.1039/C4RA10717A

Abstract

The complex [Cu(L-Tyr)2(H2O)]·H2O (1) (L-Tyr = L-tyrosine) was obtained as crystals and characterized by X-ray, spectroscopic (FT-IR, FT-Raman, NIR-vis-UV, and EPR) and magnetic methods. The monomeric complex crystallized in the monoclinic P21 symmetry with a = 11.967 (1) ?, b = 5.9986 (4) ?, c = 14.936 (1) ?. 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 (τ = 0.11). The distance of about 5.998(1) ? [Cu(L-Tyr)2(H2O)] units is involved in a polymeric chain based on N(1)–H?O(4)vi and N(2)–H?O(5)vi hydrogen bonds. The d–d band found in the polycrystalline-reflectance spectrum at 15?700 cm?1 is composed of three 2B1(dx2–y2) → 2A1 (dz2), 2B1 → 2B2(dxy) and 2B1 → 2E (dxz ≈ dyz) 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‖ = 2.236 and g⊥ = 2.063) and DMSO frozen solution (g‖ = 2.250, g⊥ = 2.055, and A‖ = 180 G) correspond to an axial symmetry of the Cu(II) coordination geometry with the dx2–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 (|D| = 0.0468 cm?1, g‖ = 2.238, g⊥ = 2.06 and A‖ = 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?O hydrogen bonds.

Graphical abstract: Structural, spectroscopic and magnetic properties of a novel copper(ii) l-tyrosinato complex
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