Judith Felcman

Chromium in plants. Comparison between the concentration of chromium in Brazilian nonhypo and hypoglycemic plants.

Chromium is an essential trace element and is associated with some biological pathways, especially with glucose tolerance. For these reasons, we decided to determine the concentration of chromium in two sets of Brazilian medicinal plants. The first group consisted of plants that are considered as antidiabetic, whereas the second included plants that do not have this therapeutic property. The concentration of chromium was determined by flameless atomic absorption. All the plants analyzed contain chromium in the normal range for this element, but the hypoglycemic plants contain more chromium than the others (1–4 μg/g compared to 0.5–1.5 μg/g).

Anhydrous copper(II) hexanoate from cuprous and cupric oxides. The crystal and molecular structure of Cu2(O2CC5H11)4

Abstract The synthesis and spectroscopic, magnetic and structural characterization of a complex of copper(II) with hexanoic acid, Cu2(O2CC5H11)4 are described. The same complex is formed by synthesis using either CuO or Cu2O. The compound exhibits a typical dinuclear paddle-wheel type structure, consisting of two copper(II) ions in square-pyramidal geometry bridged by four carboxylate anions in the xy plane. The IR spectrum shows that the ΔνCOO for this complex appears at 171 cm−1 which corresponds to a bridging bidentade mode of coordination of carboxylate-to-metal. Elemental analysis, EPR spectra and TG analysis were also performed. The magnetic susceptibility measurement confirms the antiferromagnetic nature of the copper–carboxylate coupling which is in agreement with the X-ray crystallography results.

Correlation between five minerals and the healing effect of Brazilian medicinal plants

A great many Brazilian medicinal plants are used in wound healing. They are usually applied directly to wounds, somein natura as poultices, some as dried powders, and others as water extracts (teas) for bathing. Sixteen plants from the Atlantic Rain Forest of the State of Rio de Janeiro in Brazil were analyzed to determine the concentration of five minerals: silicon, manganese, iron, copper, and zinc to study their possible role in the healing processes. The analysis was performed in plant samples and in teas prepared from them. There appears to be a correlation between the healing effect of the plants and their content of these element.

FT-IR vibrational spectrum and DFT:B3LYP/6-31G and B3LYP/6-311G structure and vibrational analysis of glycinate-guanidoacetate nickel (II) complex: [Ni(Gly)(Gaa)].

The glycinate-guanidoacetate nickel (II) complex was synthesized and obtained as a crystalline powder. The characterization of this complex was performed by means of the experimental methods: CHN-O elemental analysis, atomic absorption spectrometry, thermo-gravimetric analysis and infrared spectrum. Density functional theory calculations, DFT:B3LYP/6-31G and B3LYP/6-311G, were performed for the determination of geometrical structure and vibrational assignment for the glycinate-guanidoacetate nickel (II) complex. A full discussion of the framework vibrational modes was done using as criteria the study of the distorted geometric structures generated for each one of the vibrational modes in the low energy region. As results of this research we have obtained and characterized a novel complex, glycinate-guanidoacetate nickel (II), [Ni(Gly)(Gaa)], and we deduced the most probable structure using the experimental data of the infrared spectrum in conjunction with the theoretical DFT procedures. The calculated DFT spectra in the high and low energy regions agree well with the observed ones.

Metal complexes of N-hydroxy-imino-di-α-propionic acid and related ligands

Abstract N-hydroxy-imino-di-α-propionic acid, the ligand present in the natural oxovanadium(IV) complex ‘amavadin’ which occurs in the toadstool Amanita muscaria , has been synthesised, as well as two related ligands—N-hydroxy-iminodiacetic acid and imino-di-α-propionic acid—useful for comparison purposes. The formation of complexes of these ligands with VO 2+ , Ni 2+ has been studied and their stability constants have been determined. The two N-hydroxy-substituted ligands, of low basicity, form ML 2 complexes with VO 2+ , unlike the more basic derivatives of iminodiacetic acid. Since substitution of ligands bonded to the apical site trans to the oxo ligand is very fast and the formation of ML 2 complexes of VO 2+ exposes that apical site to the reaction media, this may be the reason why oxovanadium(IV) and the unusual derivative of iminodiacetic acid present in ‘amavadin’ were selected for the biological role that this complex plays in the toadstool.

Fourier-transform infrared and Raman spectra, and ab initio calculations for cadmium-n-di-iso-propylphosphorylguanidine-di-chloride (CdDPGCl2) complex

Cadmium-n-di-isopropylphosphorylguanidine-di-chloride (CdDPGCl2) was synthesized in the solid phase and characterized previously. The Fourier transform infrared and Raman spectra of (CdDPGCl2) in the solid state were recorded and analyzed. Emphasis was placed on the vibrational assignment of the [(O2P=O-[CdCl2]-HN=C) fragment of the complete molecular structure. With the aim of assisting the vibrational assignment of the experimental spectra, a comparison with the spectra of N-di-isopropylphosphorylguanidine ligand was carried out and ab initio calculations have been performed with several effective core potentials and valence basis sets (Hay-Wadt (HW) and Stevens-Basch-Krauss (SBK)). Due to our limited computational resources, hydrogen atoms replaced the isopropyl groups. The calculated geometrical parameters showed excellent agreement with the experimental, as well as the RHF/MP2 calculated infrared wave numbers, when compared to the IR/Raman experimental wave numbers.

A potentiometric study of guanidinoacetic acid complexation with the ions Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II)

Foi estudado a complexacao do acido guanidoacetico (AGA) com alguns ions de interesse biologico, a saber : Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) e Pb(II). Apos o AGA ter sido sintetizado e caracterizado, foram determinadas potenciometricamente as constantes de dissociacao deste ligante, assim como a de formacao de seus complexos e hidroxicomplexos com os ions supracitados. A maioria dos ions estudados formou complexos do tipo MAGA, M(AGA)2 e M(AGA)3. O Zn(II) e o Cu (II) nao formaram as especies M(AGA)3 e MAGA(OH)3 . A hidrolise dos complexos CuAGA e ZnAGA iniciou-se em pH proximo de 6-7 e para as demais especies MAGA, em pH proximo de 8, sendo que apos estes valores houve a predominância de especies polimeras hidrolisadas.

Fourier transform infrared and Raman spectra, and AB initio calculations for cadmium(II)-cysteinate glycinate complex [Cd(Cys)(Gly)]

The cysteinate glycinate cadmium(II) complex was synthesized and structural analysis was carried out using the following methods: determination of the C, H, N, S and O contents, thermogravimetry, infrared and Raman spectra. The most probable structure for the complex at a minimum of energy was calculated by the density functional theory (DFT):B3LYP/3-21G quantum mechanical method. The infrared and Raman spectra were analyzed and bands assigned through the DFT procedures, the stabilization energy being equal to: E(RB+HF-LYP)= -6442.67784a.u. Features of the infrared and Raman spectra confirm theoretical structural prediction with respect to the metal-ligand bonds: Cd-O, Cd-S and Cd-N. Full assignment of the vibrational spectra was also supported by a carefully analysis of the distorted geometries generated by the normal modes.

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.

Study of copper(II) ternary complexes with phosphocreatine and some polyamines in aqueous solution

Ternary systems of Cu(II) with phosphocreatine (PCr) and the polyamines (PAs), ethylenediamine (en), 1,3-diaminopropane (tn), putrescine (Put), spermidine (Spd), and spermine (Spm), were investigated in aqueous solution through potentiometry, ultraviolet-visible, EPR and Raman spectroscopy. The binary complex CuPCr was also studied by Raman spectroscopy, and the calculation of the minimum stabilization energy was done assuming this molecule in aqueous solution. The stability constants of the CuPCrPA ternary complexes were determined by potentiometry (T=25°C, I=0.1 mol L(-1), KNO(3)). The stability order determined was CuPCrSpm>CuPCrSpd>CuPCren>CuPCrtn>CuPCrPut, the same order of the corresponding binary complexes of Cu(II) with these polyamines. The evaluation of intramolecular PA-PCr interactions in protonated and deprotonated species of ternary complexes was carried out using the equation Δlog K=log β(CuPCrPAHq+p)-(log β(CuPAHq)+log β(CuPCrHp)). All of the CuPCrPA ternary complexes have a square planar structure and are bonded to PCr through the nitrogen atom of the guanidine group and the oxygen atom of the phosphate group, and to the PAs through two nitrogen atoms of the amine groups. The structure of the complex CuPCrSpm is planar with distortion towards tetrahedral. Calculation of the minimum stabilization energy for the CuPCr and CuPCrenH complexes confirmed the proposed coordination mode.