Alkynyl-Protected Au22(C≡CR)18 Clusters Featuring New Interfacial Motifs and R-Dependent Photoluminescence.

A series of homoleptic alkynyl-protected gold clusters Au22(C≡CR)18 were newly synthesized using 3-ethynylthiophene (ETP-H), phenylacetylene (PA-H), 3-ethynyltoluene (ET-H), and 3-ethynylanisole (EA-H). Single-crystal X-ray diffraction analysis on Au22(ETP)18 revealed that a bitetrahedral Au7 core is protected by novel Au3(ETP)4 oligomers and a Au6(ETP)6 ring, composed of R-C≡C-Au(I)-C≡C-R units bridged by π-Au-π bonds. UV-visible and 1H NMR spectroscopy revealed that the R groups did not affect the geometric and electronic structures of Au22(C≡CR)18, whereas the photoluminescence quantum yield was dependent on the R group and showed the highest value of 4.6% when R = Ph.