Jussara De Miranda

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 (H2Gaa), the essential precursor of creatine, plays an important role in our organism. However, H2Gaa interaction with metal ions has not yet been studied. We have previously studied H2Gaa complexation with some metallic ions in solution. In this study, Cr(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of H 2Gaa 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 °C. 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(H2Gaa)NO3Cl and octahedral in Cr(HGaa)3, CoH2Gaa(HGaa)2 and NiH2Gaa(HGaa)2.

The nitrate dihydrate of an aquadicopper(II) complex cation with guanidinoacetic acid and a novel trianionic disubstituted guanidine as ligands at 120 K.

The structure of the title compound, aqua[mu-(N(1)-carboxylatomethylguanidino)oxidoacetato](mu-guanidinoacetic acid)dicopper(II) nitrate dihydrate, [Cu(2)(C(5)H(6)N(3)O(5))(C(3)H(7)N(3)O(2))(H(2)O)]NO(3) x 2H(2)O, contains two enantiomers of the dicopper(II) complex cation that comprise water, neutral zwitterionic guanidinoacetic acid and the trianion of (N(1)-carboxymethylguanidino)hydroxyacetic acid as ligands. Extensive hydrogen bonding creates three-dimensional connectivity but is largely confined to layers that each contain both cation enantiomers. These layers are related to one another by crystallographic symmetry and are therefore identical in composition and connectivity.

Evaluation of the Behavior of Hydrotalcite Like-Materials for CO2 Capture

Several compounds are being investigated for CO2 capture, besides alkolamines, including solid materials as activated charcoal, zeolites, metal organic frameworks, metal oxides and hydrotalcites. Hydrotalcites, also called layered double hydroxides (LDHs), present some characteristics that are very interesting for CO2 capture, including their speed to achieve equilibrium and their high regeneration. These compounds can be represented by the general formula [M1-x2+Mx3+(OH)2]x+ [(An-)x/n.yH2O]x, where M2+ and M3+ are divalent metals and trivalent cations, respectively, and An- is an anion of valency n which occupies the interlayer region, and maintains electrical neutrality of these materials. In the present work, we have synthesized specific LDHs, thermally modified for CO2 sorption. LDH’s were synthesized intercalated with carbonate anions employing the heterogeneous precipitation method, also known as co precipitation method. After LDHs calcination at different temperatures, the formation of oxides was observed with different surface areas and therefore a varied adsorption capacity. The products were characterized by X-ray diffraction, infrared absorption spectroscopy and thermo gravimetric analysis. The maximum efficiency of CO2 adsorption was observed at reduced pressure with the calcined sample of LDH-CO3, Mg2Al which indicates that the material maintained stable and with a high crystallinity. These properties presented for LDH-CO3, Mg2Al synthesized in this work indicate that these materials can be good and also cheap candidates for CO2 capture.