Unusual Scaffold Rearrangement in Polyaromatic Hydrocarbons Driven by Concerted Action of Single Gold Atoms on a Gold Surface

Abstract

Chemical transformation of polyaromatic hydrocarbon (PAH) molecules following different reaction strategies has always been the focus of organic synthesis. In this work, we report the synthesis of a PAH molecule, formation of which consists of an unusual CÀ C bond cleavage accompanied by a complex πconjugated molecular scaffold rearrangement. We demonstrate that the complex chemical transformation is steered by concerted motion of individual Au 0 gold atoms on a supporting Au(111) surface. This observation underpins the importance of single-atom catalysis mediated by adatoms in on-surface synthesis as well as catalytic activity of single Au 0 atoms facilitating cleavage of covalent carbon bonds.

Controlled Hierarchical Dehydrogenation Reactions on Au(111)

“…On-surface dehydrogenation reactions can overcome such limitations since the only byproduct is hydrogen gas, which desorbs from the surface at low temperatures. − Since X–H (X = N, C, O...) bonds are abundant among organic precursors, hierarchical dehydrogenation reactions with high selectivity become particularly challenging. The difficulty arises not only from the high activation barriers of X–H bonds but also from monitoring hierarchical dehydrogenation reaction processes with single molecular resolution.…”

Structural Expansion of Cyclohepta[def]fluorene towards Azulene‐Embedded Non‐Benzenoid Nanographenes

“…This bond cleavage will allow the central part of the molecule to planarize, increasing the molecule‐surface interaction and reducing the vertical strain of the molecule [38] . The full mechanism of cleavage of C−C bonds by surface strain has been previously reported and can happen via hydrogenation [39] or mediated by a gold adatom [40] …”

“…[38] The full mechanism of cleavage of CÀ C bonds by surface strain has been previously reported and can happen via hydrogenation [39] or mediated by a gold adatom. [40] Next, we investigated the structural arrangement of the "croissant-like" shape species 3 and 3'. Most of them exhibit a peripheral bright protrusion (see species 3 in STM image, Figure 3a).…”

Highly Selective On-Surface Ring-Opening of Aromatic Azulene Moiety

“…We further introduce a surface adatom to the key reaction steps (refer to Figure S11 for structures of all intermediates and their transition states with adatoms), as they are well-recognized to play an important role in various on-surface reaction processes − and lower the reaction barrier significantly. − As shown in the inset of Figure , the reaction barrier of the ring rearrangement process in the presence of the Au adatom is 0.81 eV, which is significantly lower than the barrier without the Au adatom (3.20 eV). However, introducing the Au adatom does not substantially impact the reaction barriers of the ring-closing and ring-opening processes.…”