Supramolecular assemblies in [Cu(L-Arg)2(H2O)]C2O4·6H2O complex – Structural, spectroscopic, magnetic and thermal behavior

Abstract

The reaction of l-arginine and oxalate ions with copper(II) salts yields a new complex with formula of [Cu(L-Arg)2(H2O)]·C2O4·6H2O (1) (where L-Arg = L-arginine). Single crystals of 1 were synthesized by crystallization from aqueous solution. The complex properties were characterized by X-ray diffraction, spectroscopy (FT-IR, FT-Raman, NIR-Vis-UV and EPR) as well as thermal and magnetic methods. The square pyramidal (SP) geometry around Cu(II) ions in [Cu(L-Arg)2(H2O)]2+ cation complex is formed by two cis-chelated l-arginine zwitterions and a water molecule coordinated in the apex of square pyramid. The trigonality distortion of SP geometry is relatively small, τ = 0.0087. The solid state EPR spectrum showed broad hyperfine splitting with g⊥ = 2.061 at 77 K. The copper centres distanced at 7.558(5) Å are joined in a single zig-zag structure via a chain based on the combination of CuO(5)H(29)⋯O(2)C1O1Cu hydrogen bonds along the b axis (d (O2⋯O5) = 2.812 Å). Taking into account the structural features, the magnetic susceptibility data were best-fitted, giving the exchange parameter J = −0.16 cm−1. Complex 1 is thermally stable up to 66 °C, where it was observed to lose the crystallization water molecules with an 11.7% mass loss (calc. 11.5%).