Photoinduced electron transfer and electronic energy transfer in naphthyl-appended cyclams

A series of novel macrocyclic tetraaza ligands that incorporate a naphthale ne moiety as a photoactive chromophore have been prepared and structurally characterized as their Cu(II) complexes. Variable-temperature photophysical studies have concluded that the luminescence quenching evident in the Cu(H ) complexes is due to intramolecular electronic energy transfer (EET). In t heir free-base forms, these ligands undergo reductive luminescence quenchin g via photoinduced electron transfer (PET) reactions, with proximate amine lone pairs acting as electron donors. Consequently, the emission behavior c an be modulated by variations in pH and/or the presence of other Lewis acid s such as Zn(H).