Complexation behaviour of C- and N-functionalized tetradentate ligands based on 1,5,9-triazacyclododecane

The synthesis and aqueous complexation behaviour of C- and N-linked o-hydroxyaryl substituted derivatives of 1,5,9-triazacyclododecane is reported, The N-linked ligand forms strong 1:1 complexes with copper and zinc (log K-ML = 18.7 and 14.1, respectively) in which the phenolate acts as an effective donor ligand in the putative tetrahedral complex, The ligand substituted at carbon at the 3-position is less basic and forms much weaker complexes with Cu2+, Ni2+ and Zn2+ (log L(CuL) 10.2, log K-ZnL 7.32 and log K-NiL 6.11) in which phenolate participation is absent.