Synthesis, characterization and properties of new fully n-alkylated 14-membered tetraaza macrocycles and their copper(II) complexes

Abstract

New fully N-alkylated 14-membered tetraaza macrocyles 3,14-dimethyl- 3,14-dimethyl-2,6,13,17-tetraethyl-2,6,13,17-tetraazatricyclo[16.4.0. 1.180. 7.12]docosane ( 3) and 3,14-dimethyl-2,6,13,17-tetrakis(n-propyl)-2,6,13,17-tetraazatricyclo[16.4.0 1.180. 7.12]docosane ( 4) have been prepared from direct reactions of 3,14-dimethyl-2,6,13,17-tetraazatricyclo [16.4.0 1.180. 7.12]docosane ( 1) with appropriate alkyl bromides. The protonation constants of 3 and 4 were determined by a potentiometric method, and it was found that these ligands have a higher proton affinity than 1 and its tetra-N-methyl derivative ( 2). The new macrocyles react with the dehydrated copper(II) ion to form the stable complexes [Cu(L)] 2+ ( L = 3 or 4 ) in an ethanol solution, but do not react with hydrated copper(II) or nickel(II) ions in the same solution. The effects of the N-alkyl groups on the protonation and complexation behaviours of the macrocycles and on the spectroscopic and redox properties of their copper(II) complexes are presented.