Alkynyl-Protected Au22(CCR)18 Clusters Featuring New Interfacial Motifs and R-Dependent Photoluminescence

A series of homoleptic alkynyl-protected gold clusters Au-22(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 Au-22(ETP)(18) revealed that a bitetrahedral Au-7 core is protected by novel Au-3(ETP)(4) oligomers and a Au-6(ETP)(6) ring, composed of R-C C-Au(I)-C C-R units bridged by pi-Au-pi bonds. UV-visible and H-1 NMR spectroscopy revealed that the R groups did not affect the geometric and electronic structures of Au-22(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.