Mounting Freestanding Molecular Functions onto Surfaces: The Platform Approach

Abstract

A modular system has been developed to mount molecules upright onto metal surfaces in a well controlled geometry. The approach is based on a reactive platform (triazatriangulenium salt) with an electrophilic center. Functional molecules are attached via C-C bond formation. The distance from the surface can be varied by a spacer, and the distance of the functional units from each other by the size of the platform. Self-assembly of the parent triazaangulenium salt as well as the functionalized platforms on Au(111) surfaces results in stable, hexagonally ordered adlayers.

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

“…As shown in our previous publication 28 and illustrated in Fig. 2a-d these molecules form hexagonally ordered adlayers, indicative of a planar adsorption geometry.…”

“…28 As shown now for a variety of different molecules exhibiting different functional units with various head groups as well as with two types of side chains, structurally highly defined adlayers can be formed whose intermolecular spacing is solely determined by the adsorbed TATA platform rather than by packing of the vertically oriented functional groups. This affords the preparation of functionalized surfaces with attached freestanding molecular functions, that possess excellent stability under a broad range of conditions.…”

“…The substances were synthesized following the procedure described in our previous paper. 28 The quality of all substances was verified by NMR and mass spectroscopy, indicating a purity better than 99%.…”

“…In our previous publication we recently demonstrated a novel concept for attaching molecular functions to metal surfaces that combines the advantages of both approaches. 28 This new approach employs customizable molecular platforms based on the triazatriangulenium (TATA) ion (Fig. 1), which allows covalent attachment of a functional group to the central carbon atom.…”

Brownian molecular rotors: Theoretical design principles and predicted realizations

“…The platform offers the practical advantage of well-defined monolayer assembly on surfaces. 25 Also, attaching substituents of different sizes on the platform periphery makes it possible to tune the lateral distance between the switching molecules in the monolayer. In this way, close contacts that could hinder the photochemical switching and/or the rotor action can be avoided.…”