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 (UO2 2+) 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.

1,2-, 1,3-, and 1,4-Phenylenediacetate Complexes of the Uranyl Ion with Additional Metal Cations and/or Ancillary N-Donor Ligands: Confronting Ligand Geometrical Proclivities

“…Complexes 13 and 14 are nearly non-emissive, probably due to the d block metal cation present (Cu II and Ni II , respectively) providing nonradiative relaxation pathways. [49][50][51][52][53][54] In all other cases, the spectra display the usual fine structure associated with the vibronic progression corresponding to the S11  S00 and S10  S0 ( = 0-4) electronic transitions 55 (Figures 13 and 14). In all these cases in which well-resolved spectra are obtained, the uranium centres are in tris-chelated hexagonal bipyramidal environments.…”

Zero-, mono- and diperiodic uranyl ion complexes with the diphenate dianion: influences of transition metal ion coordination and differential UVI chelation

“…Uranyl emission of 7 appears to be largely quenched, either through preferential absorption of the 420 nm radiation by Ni II , 46 or through the latter providing a route for energy transfer and nonradiative relaxation, as frequently observed with d-block metal cations. [47][48][49][50][51][52] The large, most intense peaks in 7 have maxima at about 484, 504 and 522 nm. Uranyl cations in complexes 4 and 5 have six oxygen atoms as equatorial donors, and 3 has four oxygen and two nitrogen donors, and the maxima positions in their spectra are in agreement with those generally observed in similar complexes, while the values for 7, with five oxygen donors, are somewhat smaller than usual.…”

Synthetic, structural, and luminescence study of uranyl coordination polymers containing chelating terpyridine and trispyridyltriazine ligands

“…These peaks arise from electronic transitions between the LUMO 5f non-bonding uranyl orbitals and a HOMO UO sigma orbital within UO 2 2+ and are commonly referred to as ligand-to-metal charge transfer (LMCT) states. 10,18,60 While water is known to act as an efficient quencher of f-localised excited states (of both lanthanides and actinides) via coupling to the O-H vibrational manifold, 61 the emission from the uranyl LMCT excited state does not display such predictable sensitivity to water. 10,18,60 While water is known to act as an efficient quencher of f-localised excited states (of both lanthanides and actinides) via coupling to the O-H vibrational manifold, 61 the emission from the uranyl LMCT excited state does not display such predictable sensitivity to water.…”

“…The degree of oligomerization is generally influenced by pH, temperature, or concentration of uranyl species in aqueous preparations. [17][18][19][20][21] The incorporation of a secondary metal center often imparts additional properties to the overall material as well, including tuned uranyl emission using a transition metal (Fe 2+ ) 19 or sensitization of a lanthanide (Sm 3+ ) by uranyl via energy transfer. Common ligands used in the construction of uranyl CPs include the hard O-donor dicarboxylates, [6][7][8][9][10][11] and phosphonates, [12][13][14][15][16] due to their affinity for uranyl centers.…”