Self-assembly of triazatriangulenium-based functional adlayers on Au(111) surfaces

Abstract

EditorialInterfacial systems chemistry: out of the vacuum-through the liquid-into the cell Phys. Chem Detailed scanning tunneling microscopy studies of the attachment of freestanding molecular functions to Au(111) surfaces via self-assembly of functional molecules based on triazatriangulenium platforms are presented. As shown for molecules with side chains of different length and phenyl, azobenzyl, or azobenzyl derivatives with different terminal groups (iodo, cyano, or dimethyl) as functional units, this approach allows the preparation of very stable, hexagonally ordered adlayers. The intermolecular spacings in these adlayers are independent of the attached functions with the latter being orientated perpendicular to the Au surface. Due to their open structure, adlayers of platforms with attached functional groups exhibit a tendency towards bilayer formation, which can be suppressed by derivatization with appropriate terminal groups.

Adlayers based on molecular platforms of trioxatriangulenium

“…Otherwise, the morphology of the Au substrate is only marginally affected by the formation of these adlayers, similarly as for TATA adlayers. 3 A surprising result of these studies is the relatively low surface density of the TOTA and Me-TOTA adlayers of 0.053 monolayers (ML). In particular, this is significantly lower than that of Pr 3 -TATA adlayers, which form a ð ffiffiffiffiffi 13 p  ffiffiffiffiffi 13 p ÞR13:9…”

“…2d), as also previously identified for Oct 3 -TATA adlayers. 2,3,5 High-resolution STM images ( Fig. 2a and b, inset) reveal the triangular shape of the molecules, indicating a planar adsorption of the bare and vertically functionalized platforms and a uniform orientation of the molecules.…”

“…4 Adlayers of these compounds have been studied by STM, 2,3,5 different spectroscopies, 5 and electrochemical methods. 5,3 Using these techniques the TATA derivatives were shown to form hexagonally-ordered adlayers where the platforms adsorb flat on the metal substrate, the intermolecular distances can be varied by the attached side groups, and the central functional groups are oriented perpendicularly to the surface. Although this approach turned out to be an excellent method for preparation of highly-ordered functional adlayers, the employed TATA platforms have some disadvantages.…”

“…1 We recently introduced the platform approach for preparation of wellordered adlayers with freestanding functional groups on metal surfaces and illustrated its feasibility by employing derivatives of the triazatriangulenium (TATA) ion. [2][3][4][5] The triangularshaped TATA platform can be functionalized either vertically at the central carbon or laterally at the outer nitrogen atoms and thus serves as a chemically very modular and versatile template. Up to now, more than 30 TATA derivatives with different functional groups have been synthesized.…”

Triazatriangulene platform for self-assembled monolayers of free-standing diarylethene

“…It has been reported that the TATA platforms could provide sufficient space for various functional molecules to be free-standing in the SAMs, such as azobenzene derivatives [32][33][34] and porphyrins [35]. In these systems, the functional units keep independent from neighbors due to large distance between them, which is a critical feature to enable the fast response of functional moieties within the monolayers [33].…”