Uranyl Sensitization of Samarium(III) Luminescence in a Two-Dimensional Coordination Polymer
AuthorKnope, Karah E.
de Lill, Daniel T.
Rowland, Clare E.
Cantos, Paula M.
de Bettencourt-Dias, Ana
Cahill, Christopher L.
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Heterometallic carboxyphosphonates UO22+/Ln3+ were prepd. from the hydrothermal reaction of uranyl nitrate, lanthanide nitrate (Ln = Sm, Tb, Er, Yb), and phosphonoacetic acid (H3PPA). Compd. 1, (UO2)2(PPA)(HPPA)2Sm(H2O)�2O (1) adopts a two-dimensional structure in which the UO22+ metal ions bind exclusively to the phosphonate moiety, whereas the Ln3+ ions are coordinated by both phosphonate and carboxylate functionalities. Luminescence studies of 1 show very bright visible and near-IR samarium(III)-centered emission upon direct excitation of the uranyl moiety. The Sm3+ emissive state exhibits a double-exponential decay with lifetimes of 67.2 � 6.5 and 9.0 � 1.3 ?s as measured at 594 nm, after excitation at both 365 and 420 nm. No emission is obsd. in the region typical of the uranyl cation, indicating that all energy is either transferred to the Sm3+ center or lost to nonradiative processes. Herein the authors report the synthesis, crystal structure, and luminescent behavior of 1, as well as those of the isostructural terbium, erbium, and ytterbium analogs. [on SciFinder(R)]