Complex Formation of Thorium(IV) Ion with Glycyl−Glycine and Glycyl−Valine

Abstract

The protonation equilibria of glycyl-glycine and glycyl-valine and their complex formation with thorium(IV) ions in aqueous solution were studied over a wide range of pH values (2 to 12) using a combination of potentiometric, cyclic voltametric, and spectrophotometric methods at constant temperature (25 °C) and constant ionic strength (0.1 mol • dm -3 sodium perchlorate). The redox properties of the species obtained by the cyclic voltametry technique have confirmed the spectrophotometric results. Least-squares regression calculations are consistent with the formation of the ThL 3+ , ThHL 2 3+ , and ThL 2 2+ species for the studied systems, where L represents each peptide. Finally, the species concentrations were plotted at different pH values and discussed.

Complex Formation of the Cerium(IV) Ion with Glycyl-Glycine at Different Ionic Strengths

“…The number of experimental points (absorbance versus pH) was more than 40 (maximum 50) for each titration. It is most convenient to arrange a series of the measured absorption spectra at different wavelengths and various pH values as the rows of a matrix Y , which has been described in detail in our previous work. ,− …”

“…Thus, the separation, analysis of peptides and peptide hormones, and determination of their stability constants with metal ion complexes has become increasingly important for an ever-widening range of research disciplines. On the other hand, research results have clearly demonstrated that certain transition and actinide metal ions play a basic role in directing a number of biochemical processes. − …”

Calculation of acidic dissociation constants of glycylglycine in water at different temperatures using ab initio methods

“…The acidic dissociation constants of glycylglycine have been determined using potentiometric technique. The method of determining acidic dissociation constant was previously described [2,10] and its values are used in this work. These values are compared together with the calculated values using the Tomasi's method at the B3LYP/6-31+G(d) level of theory.…”

“…This mesomeric effect can be expressed as a resonance between two canonical forms [1]. Different experimental procedures were frequently used for the determination of acidity constants [2][3][4][5][6][7][8][9][10], but during the last two decades there has been much interest in developing a methodology enabling theoretical prediction of pK a values, using various quantum theoretical techniques. As pK a equals DG/2.303 RT, where DG is a free energy change of the dissociation reaction either in a gas or solution, acidity of a compound can be determined by the DG value [11][12][13].…”