New chelate complexes of trivalent Y and lanthanides (Eu, Ho, Yb) with a triazene N-oxide: Synthesis, structural characterization and luminescence properties

Deprotonated 3-(4-nitrophenyl)-1-phenyltriazene N-oxide reacts with YCl3·6H2O and LnCl3·6H2O (Ln = Eu, Ho, Yb) to give the monoclinic chelate complexes [Y{O2N(C6H4)NNN(O)Ph}4](Et3NH)·H2O (1) (Ph = C6H5; Et = C2H5) and [LnIII{O2N(C6H4)NNN(O)Ph}4](Et3NH)·H2O·{CH3OH∗} {LnIII = Eu (2), Ho (3), Yb∗ (4), in which the metal centers present a square antiprismatic configuration. As already observed for hydrated ammonium complexes of triazene-oxides ligands with (C6H4)−NO2 groups, multiple, effective O···H and N···H interactions hold the species in supramolecular 3D assemblies. The optical and the luminescent properties of the triazene-oxide europium complex 2 are also presented and fully discussed.