Self-Assembly and Electronic Structure of Tribenzotriquinacenes on Ag(111)

Abstract

The structure of two-dimensional layers of organic compounds on metal surfaces is of great interest for the fabrication of devices in the field of organic electronics. To progress in this area, a deeper understanding of intermolecular interactions and charge transfer processes between organic molecules and a metal substrate is required. Here, the two-dimensional self-assembly of tribenzotriquinacenes (TBTQs) on Ag(111) was studied by scanning tunneling microscopy under ultrahigh vacuum conditions. Highly ordered monolayers of tribenzotriquinacene (TBTQ) and centro-methyl tribenzotriquinacene (Me-TBTQ) were observed for the first time. At low to moderate coverage, both of these bowl-shaped molecules adsorb with the bowl opening faced downward, appearing in two orientations that are rotated by 14° from the high-symmetry axis of the Ag(111) surface. At high TBTQ coverage, extended islands with a self-assembled highly ordered windmill nanostructure dominate the surface, interspaced with nanometer-sized openings. This windmill structure is absent in Me-TBTQ, which immediately forms double-layered regions at high coverage. Scanning tunneling spectroscopy measurements, which probe the local density of states, identify a shift of the Ag(111) surface state in the presence of the TBTQ molecules. Investigations such as these into the self-assembly of curved aromatics provide a foundation for further work on the construction of multilayer nanostructures and the production of electronic devices.

Controlled Formation of Porous 2D Lattices from C3‐symmetric Ph6−Me‐Tribenzotriquinacene‐OAc3

“…It reveals a lattice constant of a tri= (4.3±0.2) nm and a corrugation of only 220 pm. The shallow corrugation suggests that there are no groups pointing out of the surface plane, in contrast to the previously observed Me‐TBTQ [26] . Therefore, we assume that the two remaining OAc groups as well as the CH 3 group have been cleaved off at this elevated substrate temperature.…”

“…As shown in Figure 1b, the C 3vsymmetric molecules exhibit a bowl shape, which is in good agreement with previous studies on TBTQ molecules. [23][24][25][26] In the crystal, these bowls face each other in a bowl-to-bowl arrangement, thus creating dimers in the lattice. The top view in Figure 1c reveals that the six phenyl rings form an alternating pattern of in-plane and out-of-plane orientations, allowing for enantiomers with opposite handedness (for details see the Supporting Information).…”

“…The shallow corrugation suggests that there are no groups pointing out of the surface plane, in contrast to the previously observed Me-TBTQ. [26] Therefore, we assume that the two remaining OAc groups as well as the CH 3 group have been cleaved off at this elevated substrate temperature. Such on-surface cleavage is also supported by the signals observed by mass spectrometry (cf.…”

Edge-On Self-Assembly of Tetra-bromoanthracenyl-porphyrin on Silver Surfaces

“…The control on the structure of supramolecular architectures on a surface is of prime importance to steer their properties. − For two-dimensional (2D) self-assemblies in a monolayer or submonolayer regime, conformational adaptation is often produced as a response to various stimuli and a transition from 2D planar to three-dimensional (3D) reticular geometry can be observed. − Porphyrins are a widely studied class of molecules exhibiting promising electronic, optical, magnetic, or catalytic properties with large interest in materials science for many applications. − Porphyrin-based thin films deposited on a solid surface can be easily processed and investigated at the molecular level by scanning probe microscopy techniques. − They most generally adopt a face-on conformation to optimize their adsorption on a metal or a HOPG surface, but an edge-on geometry can also be observed because of the presence and the size of side groups, the nature of the solvent, or the concentration. − The edge-on self-assembly is particularly attractive because it allows for charge migration along the columnar structure, thus providing particular mesoscopic properties appealing for molecular electronics. More elaborated strategies based on the use of a self-assembled monolayer (SAM) as a support have also been implemented to gain advanced control on the self-assembly of porphyrins. , …”

Synthesis of Enantiopure Hydrocarbon Cages Based on an Optically Resolved C3-Symmetric Triaminotribenzotriquinacene

“…Tribenzotriquinacene (TBTQ) and its derivatives are bowl-shaped molecules that have been widely studied as versatile organic building blocks in supramolecular and materials chemistry . Among various multiply functionalized TBTQ derivatives, C 3 -symmetrically 3-fold-substituted chiral congeners are especially important in these fields. , In particular, because of their unique molecular shape, TBTQ derivatives are important components for the construction of different kinds of organic cages.…”