Induced Chirality in Confined Space on Halogen Gold Complexes

The solubilization of HAuCl4 in toluene within optically active reverse micelles and lamellar structures formed by (1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)- dimethylammonium bromide (DMEB) has allowed us to evidence the complex phenomenology accompanying the confinement of Au salt within these nanostructures. Together with a chloride/bromide exchange process occurring in the first coordination sphere of an Au ion, UV−vis and electronic circular dichroism (ECD) spectra reveal the appearance of an induced dichroic signal attributable to Au complexes entrapped in the hydrophilic domain of the DMEB chiral nanostructures. Interestingly, change of the effective oxidation state and coordination geometry of the gold ion confined in DMEB nanostructures has been inferred by an analysis of the Au and Br X-ray Absorption Fine Spectroscopy (X-ray Absorbition Near Edge Spectroscopy and Extended X-ray Absorption Fine Spectroscopy) signals. Remarkably, bromine, not covalently bonded to the organic part, acts as the vector that transfers the chirality information on the DMEB to the gold complexes. Structural information on the HAuCl4 solubilized in DMEB reverse micelles dispersed in toluene, obtained by SAXS, indicate the formation of elongated clusters consisting of Au complexes stabilized by DMEB, confirming that the chirality transfer occurs in the micellar core of the DMEB and persists in the solid composites obtained by slow evaporation of the solvent.