Manuel Castillo

Chemistry of dithiocarbamate derivatives of amino acids. I: Study of some dithiocarbamate derivatives of linear α-amino acids and their nickel(II) complexes

Abstract The barium dithiocarbamate derivates of the α-amino acids glycine, DL-alanine, DL-2-amino- butyric acid, DL-norvaline and DL-norleucine have been synthesized. The crystal structure of the glycine derivative was determined. The anions were used to obtain the corresponding nickel(II) complexes in acid form. The complexes are diamagnetic, and coordination takes place in a near-square planar geometry around the Ni(II) ion through the sulphur atoms of the dithiocarbamate moiety, the structure having been confirmed by IR, 1 H NMR, UV-Vis spectroscopies and chemical analysis.

New PtS4 chromophores of dithiocarbamates derived from α-amino acids: synthesis, characterization and thermal behaviour

Abstract Complexes of Pt(II) with dithiocarbamates derived from α-amino acid (glycine, DL-alanine, DL-valine and DL -leucine) have been synthesized. The complexes have been characterized by chemical analysis, infrared, electronic, 1 H and 13 C NMR and X-ray photoelectron spectroscopies, magnetic susceptibilities measurements and TG and DSC analysis. The stoichiometry of these complexes is Pt:L= 1:2 and coordination around the metallic cation seems to be a distorted square-planar, dose to D 2 h . Coordination takes place through the sulphur atoms of the ligands and the carboxylic group is in a free, acidic form. 13 C NMR spectra indicate that all complexes are optically inactive due to the close vicinity of the chiral centers. Thermal decomposition of the complexes takes place through a multi-step process, the first step being a decarboxylation, followed by a complex pyrolysis that leads to metallic platinum. The thermal stability of these complexes decreases in the order Pt(gly dtc) 2 > Pt( DL -ala dtc) 2 > Pt( DL - val dtc) 2 > Pt( DL -leu dtc) 2 .

Chemistry of dithiocarbamate derivatives of amino acids: Part IV. Thermal behaviour of nickel (II) complexes

Abstract Thermal decomposition in nitrogen of nickel(II) complexes with dithiocarbamate of α-amino acids (glycine, dl -alanine, dl -valine and dl -leucine) has been studied. Decomposition takes place in four well-defined steps corresponding to: (i) loss of one ligand; (ii) formation of alkyl derivatives of 2,5-dioxopiperazine; (iii) formation of stoichiometric nickel sulphide; (iv) formation of non-stoichiometric nickel sulphide. The corresponding compounds have been characterized by chemical analysis, X-ray diffraction and infrared spectroscopy.

Complexes of molybdenum(V) and molybdenum(IV) with dithiocarbamates derived from α-amino acids. Reaction kinetics in organic solvents

Abstract The reaction between dithiocarbamate derivatives of α-amino acids (glycine, alanine, α-amino-butyric acid, norvaline, valine, norleucine, leucine and isoleucine) and sodium molybdate in acid medium leads to the formation of molybdenum(V) complexes with the general formula [Mo 2 O 3 )dtc a.a.) 4 ]·2H 2 O (a.a = amino acid). The complexes were characterized by elemental analysis, FT-IR and uv-vis spectroscopies and XPS. They are binuclear complexes with a linear oxygen bridge, the dithiocarbamate moiety acting as a bidentate ligand and thus yielding a distorted octahedral coordination for the metal cation. In organic solvents, these compounds undergo a chemical transformation, yielding complexes with the general formula [MoO(dtc a.a.) 2 ], whose synthesis is also described. These complexes were characterized using the same experimental techniques as above. The kinetics of transformation in organic media were studied, proposing a multi-step reaction mechanism, and the rate constants have also been determined.

Dithiocarbamates derivatives from α-amino acids as chelating agents for toxic metal ions

Abstract A study has been carried out in vitro on the chelating properties of several dithiocarbamates derived from α-amino acids (glycine, DL-alanine, DL-valine, DL-leucine, DL-isoleucine, and L-proline) against Pb(II) and Cd(II). The general formulae of the complexes obtained was M(dtc a.a.), where M = Pb(II), Cd(II), and (dtc a.a.) stands for the dithiocarbamate derivative. The infrared spectra show characteristic absorption bands, especially those originated by stretching modes of CN, CS, NH, and COO− moieties, in addition to other vibrations due to the hydrocarbon chains. Electronic spectroscopy has been used to evaluate the association constants of the complexes larger than 109. A slight decomposition of the dithiocarbamate molecules is observed during formation of the complexes, depending both on the nature of the dithiocarbamate and the nature of the cation, being more pronounced for Cd(II) than for Pb(II).

A new route to peptide complexes. Characterization and spectroscopic properties of some palladium(II) and platinum(II) peptide complexes

SummaryA method for obtaining peptide complexes using a polymer with a carbodiimide group is described. The advantages of a polymer containing the carbodiimide group compared to one containing diciclohexylcarbodiimide in the synthesis of peptide complexes was also studied. The polymer was used in the preparation of the following compounds,trans-PdCl2(Gly-ValOMe)2,trans-PtCl2(GlyValOMe)2, trans-PtCl2(GlyLeu-OMe)2,trans-PtCl2(GlyGluOMe)2, cis-PtCl2(GlyLeuOMe)2 andcis-PtCl2(GlyGluOMe)2.The complexes were characterized by chemical analysis, molecular weight determination and infrared and proton nuclear magnetic resonance spectroscopy.

Chemistry of dithiocarbamate derivatives of amino acids. Part III. X-ray photoelectron spectroscopy of Ba(S2CNHCH2CO2)·3H2O. I.r. and e.s.r. studies of α-amino acid-dithiocarbamate complexes of copper(II)

SummaryCoordination compounds [Cu(S2CNHCHRCO2H)2], were obtained by reaction of dithiocarbamate derivatives of amino acids with copper(II), and the products were characterized by i.r. and e.s.r. spectroscopy. The xps spectrum of Ba(S2CNHCH2CO2)·3H2O is reported.

Ionization Energies in Dithiocarbamate Derivatives of α-Amino Acids: A Spectroscopic Investigation on the Effect of the Side Chain

Abstract Ionization energies of dithiocarbamate derivatives of α-amino acids (glycine, alanine, valine, leucine) have been determined by X-Ray Photoelectron Spectroscopy. The values determined increase as the side chain in these amino acids becomes longer, a fact probably related to the different donor ability of these radicals. A parallel effect has been also observed in the precise positions of the IR absorption bands for these compounds.

Oxidation of bis(4-toluenesulphonyl-L-serinato)copper(II) to bis(formylglycine)copper(II)

SummaryOxidation of L-serine occurs on degradation of bis(L-serinato)copper(II) and at the same time copper is reduced.

The Syrthesis and Spectroscopic Properties of new Molybdenum(VI)-α-Amino Acio Complexes

Abstract New compounds of the type [Mo2O4μ-o μ-Am H+ (OH)2] (where Am H+ = glycine, L-alanine, D-proline, L-valine, DL-va-line and L-leucine in zwitterion form) were obtained from an acidic aqueous solution containing sodium molyb-date and amino acid. These compounds seem to be isostructural with each other and all are diamagnetic. Their infrared spectra show characteristic bands.