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Issue 10, 2017
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F-element metalated dipyrrins: synthesis and characterization of a family of uranyl bis(dipyrrinate) complexes

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Abstract

Using an improved, chromatography-free dipyrrin synthesis, the α,β-unsubstituted dipyrrins [RC(C4H2N)2H] (2) (R = tolyl (2tolyl), p-OMe-C6H4 (2anis), mesityl (2mes), ferrocenyl (2Fc)) were isolated in good to excellent yields. Deprotonation of 2 with Na[N(SiMe3)2] gives the alkali metal salts [Na(DME)n][RC(C4H2N)2] (3) which reacts with UO2Cl2(THF)3 to give the uranyl bis(dipyrrinates) UO2[RC(C4H2N)2]2(L) (L = THF (4R-THF); DMAP (4R-DMAP)) (R = tolyl, p-OMe-C6H4, mesityl, ferrocenyl). The THF adducts, 4R-THF, are unstable in aromatic and nonpolar solvents and rapidly decompose to 2 and an intractable uranium-containing solid. On the other hand, the DMAP adducts, 4R-DMAP, are indefinitely stable in solution. The solid-state structures of 4R-THF and 4R-DMAP reveal distorted trigonal bipyramidal geometries. In the solid-state, the dipyrrinate ligands exhibit significant distortions including bowing and, in some instances, out-of-plane equatorial N-atom coordination, likely as a consequence of steric crowding and interligand repulsion. The complexes, 4R-DMAP, have been fully characterized by NMR, UV/Vis, and fluorescence spectroscopies, and their electrochemical properties have been investigated through cyclic voltammetry. The cyclic voltammograms of 4R-DMAP display several redox features but present a reversible wave at ca. −1.9 V (vs. Fc0/+) attributable to a ligand centred reduction. Fluorescence measurements of all compounds reveal that only the mesityl derivatives 2mes, 3mes, and 4mes fluoresce with modest Stokes shift that ranges from ca. 30–70 nm, with 4mes displaying the greatest relative emission intensity.

Graphical abstract: F-element metalated dipyrrins: synthesis and characterization of a family of uranyl bis(dipyrrinate) complexes

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Publication details

The article was received on 16 Jan 2017, accepted on 10 Feb 2017 and first published on 13 Feb 2017


Article type: Paper
DOI: 10.1039/C7DT00150A
Citation: Dalton Trans., 2017,46, 3284-3294
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    F-element metalated dipyrrins: synthesis and characterization of a family of uranyl bis(dipyrrinate) complexes

    D. Bolotaulo, A. Metta-Magaña and S. Fortier, Dalton Trans., 2017, 46, 3284
    DOI: 10.1039/C7DT00150A

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