An influence of 2,2'-bipyridine side-arm on complexation equilibria of monoaza crown ethers in various solvents

The influence of 2,2'-bipyridine side-arm of monoazacrown ethers on silver(I) complexation equilibria has been investigated in various non-aqueous solvent,. The 2,2'-bipyridyl residue attached to nitrogen atom of the macrocycle significantly controls the formation of 1: 1 inclusion-type complexes by stabilizing silver ion inside the cavity. For 1:2 metal-to-ligand complexes, 2,2'-bipyridine unit only slightly increases stability constants of monoaza crown ether complexes. Opposite to the previous report, Ag2L2+ complex has not been observed; instead species of higher complexity, Ag2L32 have been found. Their presence has been proved by both spectrophotometry and potentiometry followed by advanced analysis. Studies of monoaza 12-crown ether were performed for comparison with 15- and 18-crown ethers.