Stability of the nonactin-K+ complex in aprotic media

Complexation of potassium ions by nonactin was studied by cyclic voltammetr y in several non-proton-donating media. It was found that the stability con stants, K-s, are strongly influenced by the solvents, and the corresponding logK(s) values vary inversely with the Guttmann donicity scale. Based on t he results of a simulated annealing procedure, the possible structure of th e complex with regard to the molecules of acetonitrile microsolvating the b ound cation is proposed. Accordingly, there are four carbonyl oxygens, two ether oxygens and two acetonitrile nitrogens coordinating the potassium cat ion and this results in a net coordination number of eight.