Synthesis, structure, and properties of trinuclear pivalate {Zn 2 Eu} complexes with N-donor ligands

New luminescent heterometallic complexes of Eu 3+ and Zn 2+ were synthesized: Zn 2 Eu(NO 3 )(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(NO 3 ) 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(NO 3 ) 3 ·6H 2 O, and 2,2′-bpy) affects the composition of the final reaction product: the reaction of [Zn(Piv) 2 ] n and Eu(NO 3 ) 3 ·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(NO 3 ) 3 ·6H 2 O (Zn : Eu = 3 : 1). The luminescence spectra of compounds 1–4 (Zn : Eu = 3 : 1) exhibit metal-centered luminescence of Eu 3+ . The most efficient ligand-antenna is 2,2′-bpy, which is due to the optimum position of the triplet level of this ligand.