Synthesis and coordination properties of highly preorganised polyamine macrocycles

Synthesis and characterisation of the new macrocyclic ligands L1‐L4 are reported. The ligands present one or two pentaamine moieties, each containing two piperazine rings, linked by benzene or anthracene spacers. Interaction of L1 with H⁺, Cu(II), Zn(II), Hg(II), and Pd(II) and of L3 with H⁺, and Cu(II) has been studied by potentiometric titrations in 0.15 mol dm^?3 NaCl aqueous solution at 298.1 ±0.1 K. The thermodynamic data suggest that in the metal complexes only three nitrogen donor atoms bind each metal ion. As a consequence of the low coordination number, these complexes are promising receptors for different molecules.