Publication details

Copper complexes of 6-aminopurine and 6-benzylaminopurine in aqueous methanol solutions



Year of publication 2015
Type Article in Proceedings
Conference 6th French - Czech "Vltava" Chemistry Meeting
MU Faculty or unit

Faculty of Science

Field Physical chemistry and theoretical chemistry
Keywords 6-aminopurine; 6-benzylaminopurine; copper complexes; protonation constant; stability constant; potentiometric titration; ion-selective electrode
Description In order to follow many biological processes it is important to understand the interactions between nucleic acids and their constituents with metal ions. It is known that adenine shows various probabilities of coordination with transition metal ions due to its potential donor sites. Electronically favoured coordination sites N(1) and N(3) for the metals were added by the nitrogens N(3) and N(9) due to tautomerization of the imidazole hydrogen atom between N(7) and N(9). In this contribution the protonation and stability constants of 6-aminopurine )adenine) or 6-benzylaminopurine (BAP) and their copper complexes were determined potentiometrically by using the titrator Titrando 835 controlled by tiamo 1.2 (Metrohm, Switzerland). The experiemnts were hampered by BAP solubility and all the potentiometric experimets were conducted in aqueous methanol solutions (10% v/v CH3OH in water). The stability constants of the copper complexes were calculated for different ligand (purine):metal (copper) ratios according to the Sigel procedure. Potentiometric titrations at different temperature and at the same ionic strength (0.1 M NaCl) enabled the thermodynamic evaluation of changes in enthalpy and entropy of the complexation process. The temperature icrease leads to a decrease in the values of the stability constants suggesting an exothermic behaviour for the complexation process. On the base of thermodynamic data obtained for adenine and BAP the differences were attributed to the effect of the benzyl moiety.
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