The Orientation of Silver Surfaces Drives the Reactivity and the Selectivity in Homo‐Coupling Reactions

Abstract

Original reaction pathways can be explored in the on-surface synthesis approach where small aromatic precursors are confined to the surface of single crystal metals. The bis-indanedione molecule reacted with itself on silver surfaces in different ways, through a Knoevenagel reaction or an oxidative coupling, leading to the formation of a variety of new molecular compounds and covalently-linked 1D or 2D networks. Noteworthy, original reaction products were obtained that cannot be synthesized in traditional solvent-based chemistry. The lowest activation temperature for the homo-coupling reactions was found on the Ag(111) surface. The Ag(110) was highly selective in terms of coupling reaction type, while on Ag(100) the temperature could finely control the selectivity. The on-surface synthesis approach is shown here to be particularly efficient to produce original compounds in mild conditions, using activation temperatures as low as 200 °C. The different structures were characterized by scanning tunnelling microscopy (STM) together with X-ray photoelectron emission spectroscopy (XPS) and high-resolution electron energy loss spectroscopy (HREELS).

Controlling a Chemical Coupling Reaction on a Surface: Tools and Strategies for On-Surface Synthesis

“…Copyright 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. (b) Adapted with permission from ref (248). Copyright 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.…”

Functionalized Truxene Scaffold: A Promising Advanced Organic Material for Digital Era

“…Quite recently, Clair and coworkers have synthesized a series of conjugated compounds on silver surfaces ( 91‐94) from indane1,3‐dione by Knoevenagel condensation reaction or by oxidative coupling (Figure ). These molecules create a new opportunity in organic electronicsas well as in supramolecular chemistry …”

Two‐Sidedness of Surface Reaction Mediation

“…The selectivity of reactions can be routinely dictated by the lattice symmetry of the substrate surface, which has been extensively proven by many studies. Kalashnyk et al have also investigated the influence of the substrate symmetry on the reaction selectivity of Knoevenagel and oxidative coupling reactions by using precursor s ‐indacene‐1,3,5,7(2H,6H)‐tetrone . It turns out that Ag(110) is highly selective, Ag(100) is less selective, and Ag(111) is non‐selective toward the oxidative coupling reaction.…”

“…In addition to the difference in the products, the surface reaction conditions can be different from and tend to be milder than those in traditional wet chemistry. It has been reported that the coupling reaction of s ‐indacene‐1,3,5,7(2H,6H)‐tetrone takes place at a lower temperature on metal surfaces than that in solvents . Moreover, the polymerization of 4,4′‐diethynyl‐1,1′‐biphenyl that involves a two‐step [2 + 2 + 2] cyclization reaction on Au(111) can be performed at a lower temperature than that for the uncatalyzed alkyne cyclotrimerization from the same precursor …”