Syntheses, spectroscopic and X-ray structure analyses of two dioxouranium (VI) complexes: supramolecular framework built from O—H…O, C—H…O and stacking interactions

Abstract

Two dioxouranium(VI) complexes, [UO

Effects of preorganization in the chelation of UO22+by hydroxamate ligands: cyclic PIPO−vs.linear NMA−

“…The associated antisymmetric absorption bands appear at 934, 897, and 906 cm -1 in the corresponding ATR-FTIR spectra. These data are in excellent agreement with values reported for [UO2(PBA)(THF)2Cl] (sym = 873 cm -1 and asym = 934 cm -1 ), 40 {[UO2(FHA)2]}n (sym = 827 cm -1 ), 31 [UO2(PBA)2DMSO] (asym = 910 cm -1 ), 35 [UO2(PBA)2DMF] (asym = 895 cm -1 ). 36 Uranyl chelation in the equatorial plane significantly lowers the oscillator strength and weakens the U=O bond order as the electron-donating ability of the ligands increases.…”

“…Besides, PBAand IBPHAform isolated molecular species of [UO2(L)S] general formula, where S designates a monodentate organic solvent (MeOH, EtOH, DMF, or DMSO) unable to promote intermolecular association of the complexes unlike water. [34][35][36] Considering the uranyl bond metrics, the [UO2(PIPO)2(H2O)] structure shows U=O distances of 1.778(4) and 1.783(4) Å with O3 and O5, respectively (Table 1), which are very close to those reported for [UO2(NMA)2(H2O)] (1.785(3) Å on average) 15 and, more generally, fall into the typical range found for the other crystallographically characterized hydroxamato uranyl complexes (Table S3, see ESI †). As far as the O=U=O angle is concerned (179.2(2)°), the triatomic coordination center can be considered as essentially linear, in accordance with the angular values compiled in Table S3 for the related structures.…”

“…The orange-red color associated to both LMCT bands is a common feature among uranyl mono-and bishydroxamato complexes both in the solid state as well as in solution (vide infra). [34][35][36]40,[42][43][44][45][46] Ligand protonation equilibria Potentiometry. The protonation constants at 298.2(1) K of the conjugated bases NMAand PIPOhave been measured in triplicates by glass-electrode potentiometry in 0.1 M KNO3 solutions (black curve in Fig.…”

Uranyl(VI) binding by bis(2-hydroxyaryl)diimine and bis(2-hydroxyaryl)diamine ligand derivatives. Synthetic, X-ray, DFT and solvent extraction studies

“…For example, H 2 L 6 (salophen), has been shown to form robust neutral 1:1 uranyl chelate complexes of composition [UO 2 (L 6 )S], each incorporating a solvent molecule (S = DMF, DMSO, H 2 O) [28,29]. Ligand species of this type incorporating a short spacer group http://dx.doi.org/10.1016/j.poly.2015.01.005 0277-5387/Ó 2015 Elsevier Ltd. All rights reserved.…”

A solution- and gas-phase study of uranyl hydroxamato complexes

“…Indeed, both the symmetric (s) and antisymmetric (as) U=O stretching modes, respectively Raman and IR active, are significantly red-shifted upon chelation with hydroxamate ligands with respect to crystalline [UO2(NO3)2(H2O)2]4H2O (s = 869 cm -1 and as = 941 cm -1 ). Both complexes give rise to strong IR absorptions at 906 cm -1 , while the Raman shift occurs at 830 cm -1 for [UO2(BHA)2(H2O)]0.85H2O and 835 cm -1 in the case of [UO2(PIPO)2(H2O)], as typically observed for dihydroxamato uranyl complexes [15,[24][25][26]. A broad feature around 3200 cm -1 also attests to the presence of water.…”