Dinuclear lanthanide(III) complexes containing β-diketonate terminal ligands bridged by 2,2′-bipyrimidine

Reactions of lanthanide(III) (LnIII) salts with the polyazine bridging ligand 2,2′-bipyrimidine (bpm) and β-diketonate terminal ligands yield 16 new monometallic and bimetallic complexes of the form Ln(tl)3bpm and [Ln(tl)3]2bpm respectively, where tl = terminal ligand. Formation of the dinuclear complex is governed by the size of the lanthanide metal and the type of terminal ligand. The smallest LnIII metals form dinuclear complexes when the terminal ligand consists of an aromatic and a fluoro group. The largest LnIII metals (Pr and Nd) form only mononuclear complexes with the bpm bridging ligands regardless of the terminal ligand. The electronic spectra of the complexes is dominated by the π−π∗ transitions associated with the terminal ligand and the emission spectra are due to 4f–4f lanthanide transitions.