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Issue 3, 2018
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A square planar gold(iii) bis-(1,1′-dimethyl-3,3′-methylene-diimidazol-2,2′-diylidene) trication as an efficient and selective receptor towards halogen anions: the cooperative effect of Au⋯X and X⋯HC interactions

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Abstract

Treatment of the tricationic gold(III) [Au(MeImCH2ImMe)2](PF6)3 complex 1-3PF6 (Im = imidazol-2-ylidene) with excess halides affords complexes 1-3X (X = Cl, Br, and I), resulting from counter anion PF6/X exchange. The 1H chemical shift of the CH3 groups and particularly that of the CH2 linker in DMSO-d6 are different in the three complexes, thus suggesting selective X⋯HC interactions. Complex 13+ can therefore be used as a halide sensor in DMSO and water. The host–guest interaction between the tricationic gold(III) complex and the halides Cl, Br and I in solution and in the solid state has been investigated by means of NMR titration experiments, DFT calculations and X-ray structure analysis. The electrostatic interaction between the halides and the triple formal positive charge on the metal centre, together with the CH⋯X hydrogen bonding between the NHC ligand and halides, contributes to the formation of stable supramolecular aggregates in solution and in the solid state. The complexing properties of 13+ are strongly influenced by the nature of the solvent. Formation of the 1 : 1 and 1 : 2 species (1X2+ and 1X2+) is observed in DMSO-d6, while that of only the 1 : 1 aggregates (1X2+) is observed in D2O (X = Cl, Br, and I). Moreover, the selectivity towards the various halides is reversed in the two solvents, being in the order Cl > Br > I in DMSO-d6 and I > Br > Cl in D2O. The formation constants of the species 1X2+ and 1X2+ in DMSO and 1X2+ in water have been determined by fitting the NMR titration curves.

Graphical abstract: A square planar gold(iii) bis-(1,1′-dimethyl-3,3′-methylene-diimidazol-2,2′-diylidene) trication as an efficient and selective receptor towards halogen anions: the cooperative effect of Au⋯X and X⋯HC interactions

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Article information


Submitted
29 Sep 2017
Accepted
28 Nov 2017
First published
05 Dec 2017

Dalton Trans., 2018,47, 935-945
Article type
Paper

A square planar gold(III) bis-(1,1′-dimethyl-3,3′-methylene-diimidazol-2,2′-diylidene) trication as an efficient and selective receptor towards halogen anions: the cooperative effect of Au⋯X and X⋯HC interactions

M. Baron, A. Dall'Anese, C. Tubaro, L. Orian, V. Di Marco, S. Bogialli, C. Graiff and M. Basato, Dalton Trans., 2018, 47, 935
DOI: 10.1039/C7DT03672H

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