Study of new complexes of chromium(III), cobalt(II), nickel(II), copper(II), and zinc(II) with guanidinoacetic acid, the precursor of creatine

Guanidinoacetic acid (H(2)Gaa), the essential precursor of creatine, plays an important role in our organism. However, H(2)Gaa interaction with metal ions has not yet been studied. We have previously studied H(2)Gaa complexation with some metallic ions in solution. In this study, Cr(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of H(2)Gaa were synthesized and characterized (C, H, N, thermogravimetric analyses, infrared spectroscopy). Electron paramagnetic resonance and ultraviolet spectroscopy were also used but in aqueous solutions at 25 degreesC. In all of the cases the coordinating atoms were the alpha-nitrogen and oxygen atoms. The most probable geometry of each of the complexes is cis-square-planar in Cu(HGaa)(2), tetrahedral in Zn(H(2)Gaa)NO3Cl and octahedral in Cr(HGaa)(3), CoH(2)Gaa(HGaa)(2) and NiH(2)Gaa(HGaa)(2).