Salt effects on the formation of the rotaxane [Ru(NH_3)_5(4,4'-bpy)/β-CD/Fe(CN)_5]~-

摘要

The formation of a rotaxane from the end-capping process of a pseudorotaxane, constructed from the [Ru(NH_3)_5(4,4'-bpy)]~(2+) complex and β-CD, was studied in salt solutions. In this process the 4, 4'-bpy ligand acts as a rigid axle and the cyclodextrin (CD) as a ring or macrocycle. The stopper used was the [Fe(CN)_5H_2O]~(3-) complex. The salts used were NaNO_3, Na_2SO_4 and Ca(NO_3)_2. Results were compared with those obtained previously in pure water. A decrease of the rate constant with respect to that in water was observed in salt solutions. This behavior is explained by taking into account electrostatic aspects, although specific effects of the medium were also considered.