Abstract
New Co(II), Ni(II) and Cu(II) complexes with urea and asparagine as ligands have been synthesized in (M:L1:L2) molar ratio (where M= Co(II), Ni(II) and Cu(II), L1 =urea, and L2 =asparagine) then identified by micro analytical data, molar conductance measurements, IR, 1HNMR, Mass, UV-VIS spectroscopies and magnetic susceptibility measurements. Thermal degradation studies were carried out by thermal analysis. These complexes have the general formula [M(L1)(L2)(H2O)n]Cl. The molar conductance values in DMSO solvent show the electrolytic nature of these complexes, indicating the outer-sphere coordination of the chloride anions with metal ions. The three complexes have an octahedral structure although urea has shown two modes of coordination. Thermal analysis study shows rapid decomposition reaction for Ni complex and the highest thermal stability for Cu complex. The kinetic parameters were determined from the thermal decomposition data using the Coats-Redfern method. Thermodynamic parameters were calculated using standard relations.
Highlights
There has been renewed attention in the preparation and studies of mixed ligand transition metal complexes[1, 2] due to their new useful properties such as magnetic exchange, photoluminescence, nonlinear optical property, electrical conductivity and antimicrobial activity[3,4,5].Mixed ligand complexes containing amino acid as co-ligand are potential biomimetic models for metal-protein interaction[6]
The molar conductance values in DMSO solvent show the electrolytic nature of these complexes, indicating the outer-sphere coordination of the chloride anions with metal ions
Research has shown significant progress in utilization of transition metal complexes as drugs to treat a lot of human diseases like carcinomas, infection control, antiinflammatory, diabetes and neurological disorders[7]
Summary
Mixed ligand complexes containing amino acid as co-ligand are potential biomimetic models for metal-protein interaction[6]. Carbamide or carbonyldiamide CO(NH2)[2] (Figure 1a), which has a remarkable role in many biological processes in decomposition of proteins and amino acid catabolism, was discovered in 1828 by Wöhler when evaporating a solution containing a mixture of potassium isocyanate and ammonium sulphate[8]. The mode of urea bonding with metal ions seems to be dependent upon the type and nature of the metal, lead(II) coordinates to the nitrogen atom, whereas iron(III), zinc(II) and copper(II). There are different types of coordination of urea in its complexes with rare-earth iodides and perchlorates[10]
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