Insights into the PhC≡C/Au Interface

Abstract

The phenylethynyl group (PhCC) has attracted attention recently as a new way to passivate gold surfaces, but little is known of the interfacial structure and bonding. Here we employ density functional theory to investigate the organogold interfaces between PhCC and the flat Au(111) surface as well as between PhCC and a model gold nanocluster (Au 20 ). Although isolated PhCC prefers the three-coordinate hollow site on the perfect Au(111) surface, formation of the PhCCAu adatom CCPh motif becomes energetically preferred when the Au adatom is present, resembling the RSAuSR motif on Au(111). However, distinct from the thiolate/Au interface, the PhCCAu adatom −CCPh staple motif features π-bonding of the CC bond to the substrate Au atom in addition to the σ-bonding of the terminal carbon to the gold adatom (or the staple gold atom). Geometry optimization and simulated annealing further show that this new type of staple motif is also the preferred bonding mode of the PhCC groups on the Au 20 cluster. The novel PhCCAuCCPh motif with π-bonding to the Au substrate is expected to be a key feature of the PhCC/Au interface for gold clusters, nanoparticles, and surfaces. This insight will help structural elucidation and chemical understanding of both self-assembled monolayers of PhCC groups on gold surfaces and PhCC protected gold nanosystems.

Gold surfaces and nanoparticles are protected by Au(0)–thiyl species and are destroyed when Au(I)–thiolates form

“…For example, carbon compounds with gold are almost exclusively described in terms of the covalent form structure 1b. Indeed, gold can in some compounds be considered as a replacement atom for carbon or hydrogen, allowing description in terms of standard singly, doubly, and triply bonded structures (23)(24)(25). More generally though, organometallic compounds dominated by covalent bonding are described in terms of ionic structures, allowing for integration of these bonds with standard valence descriptions of the metal.…”

“…The relevant electrogenativities are Au 2.4, S 2.5, Se 2.4, and Te 2.1, and gold is known to form many stable compounds in its auride form (23,26). Further, covalentbonding notations such as structure 1b are usually applied to goldoxygen bonds (53,54), analogous to that used for gold-carbon bonds (23)(24)(25). Finally, strong van der Waals interactions are known to provide bonding with closed-shell ligands such as disulfides (RSSR), as well as with nitrogen bases like ammines, pyridine, and 1,10-phenanthroline.…”

Radicals Are Required for Thiol Etching of Gold Particles

“…[2] Alternatively, larger nanoparticles may be etched using excess thiol. [3] Syntheses incorporating an etching step, alternatively described as size focusing or digestive ripening, are recently shown to give high yield of many clusters including Au 18 (SR) 14 ,[4] Au 20 (SR) 16 ,[5] Au 23 (SR) 16 ,[6] Au 24 (SR) 20 ,[5b, 7] Au 25 (SR) 18 ,[8] Au 28 (SR) 20 ,[3a, 9] Au 36 (SR) 24 ,[10] Au 38 (SR) 24 ,[11] Au 40 (SR) 24 ,[12] Au 68 (SR) 34 ,[13] Au 99 (SR) 42 ,[14] Au 144 (SR) 60 ,[15] Au 333 (SR) ∼80 ,[16] and Au ∼500 (SR) ∼120 through tuning of the synthetic conditions. [17] In addition, etching is successful in production of alloys of these clusters, including Au 24 Pd(SR) 18 ,[18] Au 24 Pt(SR) 18 ,[19] and Au 144-x Ag x (SR) 60 .…”

An Alkynyl‐Stabilized Pt5Ag22 Cluster Featuring a Two‐Dimensional Alkynyl–Platinum “Crucifix Motif”

“…Jiang et al. investigated the interfacial binding of PhC≡C‐ groups on an ideal Au 20 cluster and suggested that the formation of a monomeric or a V‐shaped dimeric staple motif became energetically preferred over the other binding modes . More importantly, Wang et al.…”