Synthesis, structures and luminescent properties of a series of novel SrII-LnIII (Ln = Eu, Gd, Tb) coordination polymers

Eight novel Sr-II-Ln(III) heteronuclear coordination polymers based on pyridine-2,6-dicarboxylic acid (H(2)pda) and imidazole (im) ligands, namely, [LnSr(pda)(3)(H2O)(5)]center dot Him center dot H2O (Ln = Eu (1), Gd (2), Tb (3)), [Ln(2)Sr(pda)(6)(H2O)(5)]center dot 4Him center dot C2H5OH center dot nH(2)O (Ln = Eu (4), n = 5; Gd (5), n = 4), [LnSr(pda)(3)(H2O)(4)]center dot Him center dot 3H(2)O (Ln = Gd (6), Tb (7)), and [GdSr(pda)(3)(H2O)(5)]center dot Him center dot C2H5OH center dot 3H(2)O (8), have been prepared by employing different amounts of imidazole. X-ray crystal structure analysis reveals that these compounds exhibit a rich structural chemistry. Complexes 1-3 possess 2-D frameworks. Complexes 4-5, 6-7, and 8 exhibit three types of 1-D chain structure. The structures of the complexes could be rationally tuned via adding different amounts of imidazole. The luminescent properties of these complexes have been investigated. The results show that Eu-III and Tb-III complexes exhibit intense red and green luminescence emission which are characteristics of Tb-III and Eu-III, respectively. Solid-state quantum yield and the lifetime of these complexes are also reported.