Synthesis, Protonation and Cu II Complexes of Two Novel Isomeric Pentaazacyclophane Ligands: Potentiometric, DFT, Kinetic and AMP Recognition Studies

The synthesis and coordination chemistry of two novel ligands, 2,6,9,12,16-pentaaza[17]metacyclophane (L1) and 2,6,9,12,16-pentaaza[17]paracyclophane (L2), is described. Potentiometric studies indicate that L1 and L2 form a variety of mononuclear complexes the stability constants of which reveal a change in the denticity of the ligand when moving from L1 to L2, a behaviour that can be qualitatively explained by the inability of the paracyclophanes to simultaneously use both benzylic nitrogen atoms for coordination to a single metal centre. In contrast, the formation of dinuclear hydroxylated complexes is more favoured for the paraL2 ligand. DFT calculations have been carried out to compare …