A novel amino acid racemization in vitamin b6-amino acid schiff base copper complexes: crystal structures of aquo (5′-phosphopyridoxylidene-dl-tyrosinato) copper(II) 3.5H2O and aquo (5′-phosphopyridoxylidene-dl-phenylalaninato) copper(II) 2.5H2O

Toxic metal sequential sequestration in water using new amido-aminoacid ligand as a model for the interaction with polyamidoamines

Polyamidoamines are low cost and easily synthesized materials that may find applications in cations sequestration and water treatment. In this paper a new amido-aminoacid ligand containing methionine has been designed as a monomeric model of the corresponding polyamidoamine. The amido-aminoacid ligand has been synthesized in high yield, by reacting acrylamide and methionine via aza-Michael addition in water and mild temperature conditions. The reaction has been monitored by NMR and Raman spectroscopies and the crystal structure has been determined by X-ray diffraction analysis. The coordination ability of the ligand towards Cu²⁺ cations in water, as well as its affinity for Ni²⁺ and Co²⁺ has been studied by potentiometric and spectrophotometric techniques. The divalent metal cations sequestration from water may occur with sequential selection by changing the pH of the solution. The copper complex with two coordinated ligands has been fully characterized in the solid state by single crystal X-ray diffraction. The results are discussed with a view to use these materials in the treatment of water contaminated by toxic transition metal ions.

Structural, spectroscopic and magnetic properties of a novel copper(ii)l-tyrosinato complex

Anl-tyrosinato copper(ii) ion complex of formula [Cu(l-Tyr)₂(H₂O)]·H₂O (1) (l-Tyr =l-tyrosine) was characterized by X-ray and spectroscopic (FT-IR, FT-Raman, NIR-vis-UV, and EPR) and magnetic methods.

Luminescence and structural properties of lanthanide complexes of Schiff bases derived from pyridoxal and amino acids

Lanthanide complexes of Schiff bases (SBs) with 1:1 and 1:2 (M:Lig) stoichiometric ratios were prepared by condensation of pyridoxal (PL) and aspartic acid (Asp) or l-histidine (His), respectively, in the presence of the appropriate metal chloride as a templating agent. These complexes were studied by optical spectroscopy and single crystal X-ray diffraction techniques. Crystallographic studies of 1:1 ([Eu(PL-Asp)(H(2)O)(4)](H(2)O)) and 1:2 ([Eu(PL-His)(2)(H(2)O)(2)]Cl(H(2)O)(4)) complexes show that Eu(III) is eight-coordinate in both structures, in a distorted square antiprism environment formed by the phenolic oxygen of PL, the nitrogen atom of carbon-nitrogen double bond, oxygen atoms of the carboxylate groups of His or Asp, and oxygen atoms of the water molecules. The main species formed in aqueous solutions containing these SBs have been determined by analysis of the luminescence spectra, lifetimes of Eu(III) excited states and vibronic interaction as well as structural features of the Eu(III) coordination sphere. Possible tetradentate coordination function of SBs in aqueous solutions with relatively high concentrations as well as the potential application of the lanthanide SB complexes as new luminescence materials are discussed.