Abstract
AbstractA series of gold(I) and gold(III) complexes with N‐heterocyclic carbene ligands functionalized with a pendant thioether group (NHC‐SR) was synthesized with straightforward procedures and characterized in solution with NMR spectroscopy and ESI‐MS spectrometry, as well as in the solid state by means of single crystal X‐ray diffraction analysis. Selected experimental aspects were rationalized through relativistic DFT calculations. The gold(I) and gold(III) complexes displayed moderate in vitro cytotoxicity towards breast cancer cells MCF7.
Highlights
Late transition metal complexes bearing N-heterocyclic carbene ligands (NHCs) have found tremendous successful applications in the last few decades, for examples as homogenous catalysts, metallodrugs or luminescent materials
We decided to expand the scope of the metal complexes with such type of ligands and in this paper, we report on the synthesis, characterization and the preliminary antiproliferative results of gold(I) and gold(III) complexes bearing thioether-functionalized NHCs
The formation of the silver(I) complexes 1 and 2 has been confirmed in the 1H NMR spectra by the disappearance of the signal associated to the C2-H hydrogen; in the 13C NMR spectra, the signal of the carbene coordinated to the silver centre is clearly identifiable at d 180 ppm, in the typical range of carbene carbons bonded to silver centers.[28]
Summary
Late transition metal complexes bearing N-heterocyclic carbene ligands (NHCs) have found tremendous successful applications in the last few decades, for examples as homogenous catalysts, metallodrugs or luminescent materials. The success of this class of ligands can be attributed to their strong donating abilities, which confers to the corresponding metal complexes a very high stability, straightforward synthetic procedures and the possibility to tune their steric and electronic properties by changing the nitrogen or backbone substituents.[1,2,3,4] it is possible to introduce a second donor group (usually P, O or N)[5,6,7,8,9,10] in the pendant nitrogen substituent, giving possibly bidentate ligands.[11] In this regard, N-heterocyclic carbenes bearing a thioether pendant function (Chart 1) are an interesting class of ligands, that has found application both in homogeneous catalysis and bioinorganic chemistry These Sfunctionalized NHCs may show a chelating ability which results in the formation of highly stable complexes with a strong σ-donor function (the NHC moieties) and a weaker one (the sulfur atom).[12,13,14,15,16,17] The hemilabile equilibrium of sulfur chelating ligand can be of high importance for the development of efficient catalysts: a momentary dissociation of the heteroatom from the metal during a catalytic cycle releases a coordination site and allows the coordination of the substrate, while preserving the stability of the metal complex with the coordination of the NHC ligand. Studies on chemoprotective action and cytotoxic properties of sulfur-containing NHC ruthenium(II) and platinum(II) complexes have been reported by some of us.[24,25] We decided to expand the scope of the metal complexes with such type of ligands and in this paper, we report on the synthesis, characterization and the preliminary antiproliferative results of gold(I) and gold(III) complexes bearing thioether-functionalized NHCs
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