Thermogravimetric study of some divalent transition metal chelates of several amino acids

Abstract

Thermogravimetric studies of divalent metal chelates of eight common amino acids have revealed that no relationship exists between thermal stability orders of the chelates and hydrolytic stability orders, infrared band shifts or force constants. An attempt is made to relate thermal stability order to relative heats of formation and stereochemistry.Amino acid chelates have been studied extensively during the last two decades. A variety of instrumental techniques have been used. Their thermal stabilities, however, have not been studied in any detail.Most thermal stability work has been directed at the amino acids themselves, determining decomposition temperatures [1--3] and products of decomposition [4,5]. Differential thermal analysis curves for copper glycinate mono-and dihydrate [6], cadmium glycinate monohydrate [7] and copper alaninate monohydrate [8] have been published, along with thermogravimetric curves for copper complexes of glycine and ~-alanine [9] and cobalt(III) complexes of glycine, e-alanine and leucine [10]. It has been noted [2] that aliphatic amino acids are more stable when they have short, linear alkyl side chains rather than long branched chains. Other than this, however, no attempt has been made to correlate thermal stabilities with other structural or chemical properties.Since a number of amino acid chelates were still easily available to us, it was decided to study the thermal properties of the compounds. Accordingly, thermogravimetric data for divalent transition metal chelates of glycine, DL-~-alanine, DL-fl-alanine, DL-serine, DL-c~-amino-n-butyric acid, DL-~-aminoisobutyric acid, DL-norvaline and DL-leucine were obtained. The resulting thermal data might then be compared with other available information such as infrared data and hydrolytic stability constants of amino acid chelates and thermal stabilities of other complexes of these transition metals.

Nickel and Cobalt Complexes of Non-protein L-Norvaline and Antioxidant Ferulic Acid: Potentiometric and Spectrophotometric Studies

“…The objective of this study is to quantify the metal chelating activity of Nva and FA with Ni 2+ and Co 2+ . Besides, these compounds also show many beneficial effects for the human body, such as antioxidant, anti-inflammatory, and anticancer effects and have a therapeutic effect on tumors [21][22][23][24][25][26][27][28][29][30][31][32]. Monitoring of complex formation of ligands and metal ions was accomplished with a potentiometric technique with a glass electrode, and the experimental data were analyzed using HYPERQUAD2008 [33].…”