Synthesis and crystal structure of yttrium(III) and lanthanide(III) complexes with a new terpyridine-like ligand 2,4-bis(3,5-dimethylpyrazol-1-yl)6-diethylamino-1,3,5-triazine

A new planar aromatic tridentate terpyridine-like ligand, 2,4-bis(3,5-dimethylpyrazol-1-yl)-6-diethylamino- 1,3,5-triazine (L), has been synthesized and the structures of its complexes [YL(NO3)(3)] (1) and [LnL(NO3)(3)(H2O)]L [Ln = La (2), Ce (3), Pr (4), Nd (5), Eu (6)] have been determined by X-ray crystal structural analysis. The structures of the five lanthanoid complexes are isomorphous and isostructural but different from the crystal structure of the yttrium complex [YL(NO3)(3)]. The latter shows a nine-coordinate metal center whereas the crystal structure of the lanthanoid complexes [LnL(NO3)(3)(H2O)]L show a 10-coordinate metal center. The pi-pi stacking and hydrogen bonding between the coordinated and uncoordinated L molecules sensitized the Ln luminescence. The thermal behavior of the ligand and its complexes is discussed.