Synthesis and protonation behaviour of the macrocyclic ligand 1,4,7,13-tetramethyl-1,4,7,10,13,16-hexaazacyclooctadecane and of its bicyclic derivative 4,7,10,17,23-pentamethyl-1,4,7,10,13,17,23-heptaazabicyclo[11.7.5]-pentacosane. A potentiometric and 1H and 13C NMR study

Abstract

The synthesis and characterization of the new macrocyclic ligand 1,4,7,13-tetramethyl-1,4,7,10,13,16-hexaazacyclooctadecane (L) and of its bicyclic derivative 4,7,10,17,23-pentamethyl-1,4,7,10,13,17,23-heptaazabicyclo[11.7.5]pentacosane (L1) is reported. The basicity behaviour of both polyamines has been studied by potentiometry in 0.15 mol dm^–3 NaClO₄ solution at 298.15 K and the relevant protonation constants have been determined. ¹H and ¹³C NMR spectroscopy of L and L1, at various pH values, allows the main features of the protonation patterns to be determined.