Emissive mononuclear Eu(III) and Tb(III) complexes bearing deprotonated 2,2-bipyridyl-1,2,4-triazole terdentate ligands

A series of new emissive mononuclear Ln(III) complexes with deprotonated 2,2'-bipyridyl-1,2,4-triazole terdentate ligands, [Ln(L)(DMF)(2)(NO3)(2)].n(solvent) (Ln=Eu (1 and 2), Tb (3 and 4), HL=6-(5-trifluoromethyl-1,2,4-triazol-3-yl)-2,2-bipyridine, 6-(5-trifluoromethyl-1,2,4-triazol-3-yl)-4,4-dimethyl-2,2-bipyridine), have been synthesized and characterized. As revealed by X-ray crystallography, each Ln(III) has a distorted tricapped trigonal prism generated by three nitrogens from one 2,2'-bipyridyl-1,2,4-triazolate chelate and six oxygens from two DMF molecules and two chelating nitrates, where 2,2'-bipyridyl-1,2,4-triazole serves as a mono-anionic tridentate chelate via deprotonation of the 1,2,4-triazolyl-NH. Complexes 1-4 are all emissive at room temperature in solution and solid states, and the introduction of two methyl groups into the 2,2'-bipyridyl ring is efficient in enhancing luminescence efficiencies of Ln(III) complexes.