ω-Thioacetylalkylphosphonium salts: Precursors for the preparation of phosphonium-functionalised gold nanoparticles

Two new ω-thioacetylalkylphosphonium salts that function as masked cationic alkanethiolate ligands for the stabilisation of gold nanoparticles have been prepared. Both (3-thioacetylpropyl)triphenylphosphonium bromide and (6-thioacetylhexyl)triphenylphosphonium bromide were shown to form water-soluble gold nanoparticles of ca. 5–10 nm in size that are stable for up to six months. The related (3-thioacetylpropyl)diphenylphosphine oxide was also prepared but did not act as a stabilising ligand in gold nanoparticle formation.

Graphical abstractThe synthesis and characterisation of two new ω-thioacetylalkylphosphonium salts, (3-thioacetylpropyl)triphenylphosphonium bromide 5, and (6-thioacetylhexyl)triphenylphosphonium bromide 6 is reported. Both compounds act as ‘masked thiolate’ ligands which readily lose the acetyl group forming triphenylphosphonioalkylthiolate anions which are able to stabilise gold nanoparticles forming cationic monolayer-protected gold clusters. Thus, when compounds 5 and 6 are treated with gold(III) salts under reductive conditions, water-soluble gold nanoparticles of ca. 5–10 nm in size that are stable for up to six months are formed. The related (3- thioacetylpropyl)diphenylphosphine oxide has also prepared but is not effective at stabilising gold nanoparticles.Figure optionsDownload full-size imageDownload as PowerPoint slide