CuPYDC Metalloligands and Postsynthetic Rearrangement/Metalation as Routes to Bimetallic Uranyl Containing Hybrid Materials: Syntheses, Structures, and Fluorescence

Abstract

Treatment of a molecular copper(II) 2,4-pyridinedicarboxylate metalloligand (CuL1) and a copper(II) 2,3-pyridinedicarboxylate coordination polymer (CuL2) with the uranyl cation (UO22+) under hydrothermal conditions has yielded three new coordination polymers: [(UO2)(H2O)2(C7H3NO4)2Cu] (1), [(UO2)(H2O)2(C7H3NO4)2Cu]·H2O (2), and [(UO2)(OH)(H2O)(C7H3NO4)(C7H4NO4)Cu]·H2O (3). Compound 1 is formed upon the treatment of CuL1 with the uranyl cation to yield a one-dimensional coordination polymer. Compounds 2 and 3 are formed upon the rearrangement of the axially binding carboxylate groups in CuL2 to accommodate the uranyl cation to yield extended three-dimensional and two-dimensional topologies, respectively. Attempts to prepare compounds 1–3 via direct assembly have yet to be successful, suggesting that a prebound Cu(II) metal center may be necessary in the synthesis of these bimetallic coordination polymers. Investigation of the emissive properties and the local geometries of compounds 1–3 suggests that the aromaticity of the ligand may influence energy transfer from the uranyl cation to a Cu(II) metal center, thus tuning uranyl fluorescence.