Synthesis, structure and photophysical properties of [UO₂X₂(OPPh₃)₂] (X = Cl, Br, I)

Abstract

The synthesis of a series of uranyl compounds via oxidation of [Li(THF) ] (X = Cl, Br, I) have been measured and no significant changes in the position of the emission (515-530 nm) or the lifetimes (ca. 1 μs) are observed in this series. However a bathochromic shift is observed in the U-X LMCT band in the electronic absorption spectrum.

A Structural and Spectroscopic Study of the First Uranyl Selenocyanate, [Et4N]3[UO2(NCSe)5]

“…The U=O bond length is 1.771(2) Å and average U-N, N=C and C=Se bond lengths of 2.459 Å, 1.149 Å and 1.794 Å respectively can be compared to the uncoordinated [N=C=Se]´ion (N=C: 1.081(14) Å and C=Se: 1.846(7) Å) in 2. Upon coordination to the uranyl ion the N=C bond lengthens slightly and the C=Se bond shortens slightly, suggesting a reorganization in the π-framework of the ligand; this effect has also been observed in uranyl thiocyanates experimentally and theoretically [11,14] 8 ] (An = Th, U, Pu) [16], the lack of perturbation of the π-system in the [NCS(e)]´ligands suggests no π-overlap in the U-N bond.…”

“…A yellow precipitate was formed which was soluble in dichloromethane or acetone. We have noted that whilst this compound is air and moisture stable, it is somewhat light sensitive so reactions were conducted in the dark; the uranium(IV) compound [ n Pr 4 N] 4 [U(NCSe) 8 ] was also reported to be light sensitive [12]. Decomposition to red selenium powder was sometimes observed but the fate of the uranium was not determined.…”

“…Time resolved studies allow sometimes complex speciation in water to be deconvoluted [7], whilst in non-aqueous media the positions of the emission maxima and lifetimes can be used as electronic and structural probes. For instance in the family of complexes trans-[UO 2 X 2 (O=PPh 3 ) 2 ] (X = Cl, Br, I) the photoluminescent properties do not vary [8], but for the compounds trans-[UO 2 Cl 2 L 2 ] (L = Ph 3 P=NH, Ph 3 P=O and Ph 3 As=O) a red shift in the O yl ÑU LMCT band is observed, in line with the increased donor strength of the ligand [9]. A further interesting photophysical property of certain uranyl compounds are thermochromic effects.…”

A Uranium(VI)–Oxo-Imido Dimer Complex Derived from a Sterically Demanding Triamidoamine

“…The UV–vis–NIR spectra of 1 (Figure S8) exhibits no notable absorption bands <12000 cm –1 , suggesting no f–f transitions are present, as expected for uranium­(VI). Like A , a broad charge transfer absorption feature trails from the UV region down to ∼12000 cm –1 for 1 , and within that region, at least two bands can be discerned at ∼19000 and ∼20920 cm –1 (ε = ∼400 and ∼800 M –1 cm –1 , respectively); given the commonality between 1 and A , these absorptions most likely involve LMCT within the OU­(μ-N) 2 UO unit, since 1 is 5f 0 6d 0 . , …”

Pseudohalide Tectons within the Coordination Sphere of the Uranyl Ion: Experimental and Theoretical Study of C–H···O, C–H···S, and Chalcogenide Noncovalent Interactions

“…44 We recently showed for a series of [UO2X4] 2ions (X = Cl, Br, I) that the emission maxima and lifetimes of the Oyl→U LMCT band are not particularly sensitive to variation of the halide. 45 Recently the influence of the tecton in [UO2Cl4] 2has been interrogated using luminescence spectroscopy 46 and it may be that those ligands that have vibrational modes that can couple with the U=O vibrations to directly influence the luminescence properties. The emission and excitation spectra of RS and RSe have been recorded both in the solid state and in solution, where all non-covalent interactions break up and mononuclear species dominate.…”