Association of methyl, amino and hydroxy derivatives of adenine at a mercury electrode at various sodium chloride concentrations

Abstract

The effect of methyl, hydroxy and amino substituents on the adsorption and association of adenine on the surface of a mercury electrode at various NaCl concentrations was studied. All these substituents prevent the association and surface film formation of adenine on the negatively-charged electrode surface, where protonated unsubstituted adenine associates at low temperatures. A methyl substituent in position 3 or 6 prevents the association of adsorbed adenine derivatives not only on the negatively charged mercury surface, but also on the neutral mercury surface. 1-Methyladenine associates on the neutral mercury electrode (near −0.6 V) only at higher NaCI concentrations; 2-methyladenine associates on the neutral mercury surface well at low and high ionic strengths but less at medium ionic strengths, similarly to adenine. 2-Aminoadenine associates at low ionic strengths on the positively-charged mercury surface (near −0.2 V) and at higher NaCl concentrations on the neutral surface (near −0.7 V). 8-Hydroxyadenine did not associate on the mercury electrode. The double pit or more complicated course of the capacitance pit observed with 1-methyladenine, 2-methyladenine and 2-aminoadenine at higher NaCl concentrations may be caused by a change in the structure of the surface film.