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 [Zn-2(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)center dot 6H(2)O, and 2,2'-bpy) affects the composition of the final reaction product: the reaction of [Zn(Piv)(2)] (n) and Eu(NO3)(3)center dot 6H(2)O (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)center dot 6H(2)O (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.