Aminofunctionalized imidazolium salts: dual role players in gold chemistry

Imidazolium salts incorporating functional groups on the cation and/or anion, represent a class of compounds having great versatility due to their applications as ionic liquids (ILs) or N-heterocyclic carbene precursors (NHCs). Our research in this field has been dealing with the synthesis of (Boc)-protected and deprotected amino-functionalized imidazolium cations [NHR1CH2CH2imR2]+ ([1]+, R1 = Boc, H; R2 = Me, Bz, Trit) and related NHC-Ag(I) and Rh(I) complexes.1 We have also demonstrated that [NH2CH2CH2imMe]+ plays a dual role in gold chemistry: i) can give the gold(III)-aminoethyl imidazolium aurate salt [Cl3AuNH2(CH2)2ImMe)][AuCl4] (2) used in the preparation of catalytically active gold nanoparticle-containing polycarbonate membranes or ITO glasses;2 ii) can act as a primary amino-functionalized NHC precursor to give the dimeric, photoluminescent complex [Au2(NH2(CH2)2imMe)2][NO3]2 (3).3 We now present some very recent results of a research focused on the preparation of detonation nanodiamond(ND)/AuNPs hybrid materials. Two different experimental routes are followed for the decoration of ND by AuNPs, that are in turn prepared by an innovative electroless approach using the gold complex 2. Structure and morphology at the nanoscale level of the AuNPs-on-ND deposits have been deeply investigated by electron microscopy (FE-SEM, HR-TEM) and diffraction (XRD) techniques. The optical properties of these systems have been determined by performing scattering and UV-Vis absorption measurements and by comparing the experimental data with simulated extinction spectra. The preliminary results of the present research establish the first rules for future designs of more complex AuNPs/ND systems.