A phosphorus-based compartmental ligand, (S)P[N(Me)NCH–C6H3-2-O-3-OMe]3 (LH3), enables the assembly of luminescent heterobimetallic linear {L2Zn2Ln}+ [Ln = Gd, Tb, Nd and Eu] complexes

Abstract

The sequential reaction of a phosphorus-based trishydrazone ligand, LH₃ with anhydrous ZnCl₂ and LnCl₃·6H₂O in a 2 : 2 : 1 stoichiometric ratio in the presence of triethylamine as the base leads to the formation of monocationic trinuclear complexes [L₂Zn₂Ln]Cl {Ln = Gd (1), Tb (2), Nd (3), Eu (4) and L = [(S)P[N(Me)NCH–C₆H₃-2-O-3-OMe]₃}. All the three metal ions, in each of these compounds, are arranged in a linear fashion. The two terminal Zn(II) ions are encapsulated by three imino and three phenolate oxygen atoms while the lanthanide ion remains in the centre with an all-oxygen coordination environment. Detailed photophysical measurements reveal the complete absence of antenna sensitization in all the four complexes. However, a strong emission was found for 2 and 4 when excited directly at their f–f levels.