Covalent networks through on-surface chemistry in ultra-high vacuum: state-of-the-art and recent developments

Abstract

The fabrication of large molecular devices, directly on surfaces in UHV conditions, by covalent coupling of smaller precursors has become in the past years an attractive solution for Molecular Electronics. This review presents the state-of-the-art and an analysis of the potential of this new field, from Ullmann type C-C coupling, cyclodehydrogenation, and reactions involving heteroelements to 2D polymerisation on insulating thin films. Mechanistic insights are also mentioned, giving preliminary explanations on the influence of the substrate and the 2D confinement. Potential perspectives for further developments are then evoked.

Manipulating the Conformation of Single Organometallic Chains on Au(111)

“…15,[36][37][38] This leads in general to a second reaction step, the intermolecular Ullmann carbon-carbon coupling. 15,16,22,36,[39][40][41][42][43][44][45] Here, our initial aim was to utilize an on-surface chemical reaction to produce covalently bonded linear polymers. In order to characterize the structure of the unreacted monomer units, the I 2 TMTP molecule was deposited onto an Au(111) sample held at a temperature of approximately 30K with the C-I bond expected to remain intact upon molecular adsorption, due to the low temperature.…”

“…with more conformational flexibility, is less well studied, for example the bending of chains on a surface. [14][15][16][17] This is mainly due to the difficulties in depositing such large molecules on surfaces in a clean and intact fashion, 18 and hence alternative strategies such as the on-surface formation of organometallic [19][20][21] or covalently bonded structures 22 are utilized. Although the adsorption geometry of monomers within a Cucoordinated polymer has been studied, 23 no details of the manipulation of the conformational structure of a molecular chain or the interaction between the conformation of the chain and its overall shape has been reported upon.…”

Homo-coupling of terminal alkynes on a noble metal surface

“…Thus, it is a timely issue to explore acetylenic coupling at interfaces, and recent studies using a sequential protocol with monolayer self-assembly followed by a crosslinking step provided encouraging results 11 . Pursuing a different vein, there is the prospective research domain dealing with on-surface covalent reactions under ultrahigh vacuum (UHV) conditions on clean metal surfaces to realize novel functional nano-architectures and networks [12][13][14][15][16][17][18][19] . However, many of the employed protocols imply appreciable activation barriers or rely on the enabling character of a set of leaving groups.…”

Adsorption of Large Hydrocarbons on Coinage Metals: A van der Waals Density Functional Study

“…The assembly of organic molecules on metal surfaces into one-and two-dimensional nanoarchitectures, stabilized by either non-covalent [1][2][3][4][5] or covalent interactions, [6][7][8][9][10] has become a very active area in surface and nanoscale science over the past decade. Density functional theory (DFT) is important as a complemental tool for the experimental characterization of molecular architectures on surfaces.…”