Synthesis, structure, and properties of trinuclear pivalate {Zn2Eu} complexes with N-donor ligands

New luminescent heterometallic complexes of Eu3+ and Zn2+ were synthesized: Zn2Eu(NO3)(Piv)6(L)2 (Piv is pivalate anion, L = MeCN (1), 2,3-lutidine (2), 2,2′-bpy (3)) and [Zn2(Piv)3(2,2′-bpy)2][ZnEu(NO3)3(Piv)3(2,2′-bpy)] (4). In the case of 2,2′-bpy, the order of mixing of the reagents ([Zn(Piv)2]n, Eu(NO3)3·6H2O, and 2,2′-bpy) affects the composition of the final reaction product: the reaction of [Zn(Piv)2]n and Eu(NO3)3·6H2O (in the ratio Zn : Eu = 3 : 1) in MeCN affords complex 1 and the subsequent addition of 2,2′-bpy (Zn : L = 1 : 1) affords complex 3. Complex 4 is formed in the reaction of [Zn(Piv)2]n and 2,2′-bpy (Zn : L = 1 : 1) in MeCN followed by the addition of Eu(NO3)3·6H2O (Zn : Eu = 3 : 1). The luminescence spectra of compounds 1–4 (Zn : Eu = 3 : 1) exhibit metal-centered luminescence of Eu3+. The most efficient ligand-antenna is 2,2′-bpy, which is due to the optimum position of the triplet level of this ligand.