The kinetics of the electron transfer reaction between [Ru(NH3)(5)pz](2+) (pz = pyrazine) and [CO(C2O4)(3)](3-) (C2O42- = oxalate anion) was studied in solutions of the SB1.5G dendrimer at different concentrations of a supporting electrolyte (NaCl) and in solutions of the SB4.5G dendrimer. The results are interpreted on the basis of a modified pseudophase model, which takes into account the anti-cooperative character of the cationic reactant binding to the dendrimers. With regard to the binding characteristics of small cationic ligands, and their influences on the kinetics of reactions in which these small ions participate, the conclusion was that dendrimers and DNA behave similarly. (C) 2004 Elsevier B.V. All rights reserved.