Sodium: Dibenzo-30-crown-10 aggregates in solution: Na-23 NMR study

(n + 1):n sodium:dibenzo-30-crown-10 complexes are formed in nitromethane solutions. A model based on the coexistence in solution of 1:1, 2:1 and 3:2 complexes can account for the observed Na-23 chemical shifts, transverse and longitudinal relaxation rates. Logarithms of the equilibrium constants of formation at (25±1)°C are (2.1±0.3) and (2.5±0.3) for the 2:1 and 3:2 complexes respectively. The characteristic Na-23 relaxation rates and chemical shifts of the aggregated complexes are compatible with a structure of ion pairs linked by the crown ether.