Mono(di)nuclear Europium(III) complexes of macrobi(tri)cyclic cryptands derived from diazatetralactams as luminophores in aqueous solution

To increase the excellent light-emitting properties of the Eu3+ ion, macrob icyclic and macrotricyclic ligands 7-10, incorporating a 18-membered tetral actam ring (acting as a lanthanide binding site) and a sensitizer group (2, 2'-bipyridine or 2,2'-bipyridine 1,1'-dioxide moiety), were synthesized. Th e mononuclear and dinuclear europium cryptates derived from these ligands w ere isolated and characterized. Their luminescent properties and those of t he corresponding cryptates containing a phenanthroline group (see 11 and 12 ) were examined in H2O and D2O solutions at 77 and 300 K. It results that t he tetralactam moiety plays a major role in the efficient shielding of the complexed Eu3+ ion from the water environment. The cryptands incorporating the bipyridine unit are the most promising labels according to their photop hysical properties (excitation maxima, emission decay lifetime, relative lu minescent yield). In contrast with literature data, introduction of N-oxide groups in the bipyridine chromophore weakens the luminescence properties o f the cryptate.