Luminescence behaviour of cadmium, lead, zinc, copper, nickel and lanthanide complexes of octadentate macrocyclic ligands bearing naphthyl chromophores

Abstract

The luminescence behaviour of two macrocyclic ligands incorporating naphthyl fluorophores has been studied in water and acetonitrile. The ligands 1,4,7-tris(methylcarbamoylmethyl)-10-(2-naphthylmethylcarbamoylmethyl)-1,4,7,10-tetraazacyclododecane, 1 and 1,4,7,10-tetrakis(2-naphthylmethylcarbamoylmethyl)-1,4,7,10-tetraazacyclododecane, 2, exhibit distinctive luminescence behaviour in the presence of quenching (e.g., Pb^II, Cu^II and Ni^II) and non-quenching ions (e.g., Cd^II and Zn^II). The protonated tetranaphthyl ligand forms a well-defined excimer in which excimer emission is a sensitive probe of solvent polarity. The naphthyl group serves as an antenna for energy transfer to the phosphorescent bound europium ion and amide N–H coupling provides a significant deactivation mechanism for the excited Eu⁵D₀ state.