Simple and efficient: Ethylene glycol isonitrile gold(I) chlorides for the formation and stabilization of gold nanoparticles

Article abstract of DOI:10.1002/ejic.201100324

Ethylene glycol isonitriles C≡N(CH₂CH₂O) _nCH₃ (5a, n = 1; 5b, n = 3; 5c, n = 4) with different chain lengths were prepared by using straightforward synthesis methodologies including the Gabriel synthesis and an Appel-type reaction protocol. Upon treatment with [AuCl(SMe)₂], compounds 5a-c gave the corresponding isocyanide gold(I) chlorides [AuCl{C≡N(CH₂CH₂O) _nCH₃}] (7a, n = 1; 7b, n = 3; 7c, n = 4). Single-crystal X-ray diffraction studies reveal a polymeric (7a) or dimeric (7c) structure with aurophilic interactions. Gold(I) complexes 7a-c were applied in the formation and stabilization of gold nanoparticles (AuNPs). The isonitriles with their ethylene glycol functionalities, which provide multiple donating capabilities, are able to stabilize the encapsulated gold colloids. The reduction of 7a-c by the addition of Na[BH₄] in tetrahydrofuran or methanol produces AuNPs without the further addition of any stabilizer, since metal-organic 7a-c combine the stabilizing component and gold source in one molecule. The dependency of different solvents, concentrations, and varying ethylene glycol chain lengths on the NP size and size distribution is reported. Characterization by TEM, UV/Vis spectroscopy, and XRPD revealed that AuNPs are formed with a size between 6.4(±1.4) to 9.5(±2.3) nm in methanol and 18.2(±2.3) to 27.2(±3.5) nm in tetrahydrofuran. Copyright