Modular Bicyclophane-Based Molecular Platforms.

The modular synthesis of a series of nanoscale phenylene bicyclophanes with an intraannular orthogonal pillar is described. The compounds are obtained by a Suzuki cross-coupling condensation and are characterized by mass spectrometry and NMR spectroscopy as well as in situ scanning tunneling microscopy at the solid/liquid interface of highly ordered pyrolytic graphite. In addition, their structures and conformations are supported by quantum chemical calculations, also after adsorption to the substrate.

Influence of Different Substitution Patterns on the 2D Crystalline Aggregation of Small Molecules on HOPG Surfaces.

A series of benzoic and terephthalic acid derivatives and their corresponding ethyl esters have been synthesized. These are decorated with dendritic units carrying alkoxy chains that differ in the number of alkoxy groups and/or their substitution pattern. These molecules were deposited from solution on highly oriented pyrolytic graphite, and the resulting supramolecular surface patterns have been studied by scanning tunneling microscopy at the solid/liquid interface.

Nanoscale π-conjugated ladders.

It is challenging to increase the rigidity of a macromolecule while maintaining solubility. Established strategies rely on templating by dendrons, or by encapsulation in macrocycles, and exploit supramolecular arrangements with limited robustness. Covalently bonded structures have entailed intramolecular coupling of units to resemble the structure of an alternating tread ladder with rungs composed of a covalent bond.

Supramolecular Nanopatterns of Molecular Spoked Wheels with Orthogonal Pillars: The Observation of a Fullerene Haze.

Molecular spoked wheels with intraannular functionalizable pillars are synthesized in a modular approach. The functionalities at their ends are variable, and a propargyl alcohol, a [6,6]-phenyl-C61-butyrate, and a perylene monoimide are investigated. All compounds form two-dimensional crystals on highly oriented pyrolytic graphite at the solid-liquid interface.

Nanopatterns of molecular spoked wheels as giant homologues of benzene tricarboxylic acids.

Molecular spoked wheels with and symmetry are synthesized by Vollhardt trimerization of -symmetric dumbbell structures with central acetylene units and subsequent intramolecular ring closure. Scanning tunneling microscopy of the -symmetric species at the solid/liquid interface on graphite reveals triporous chiral honeycomb nanopatterns in which the alkoxy side chains dominate the packing over the carboxylic acid groups, which remain unpaired. In contrast, -symmetric isomers partially allow for pairing of the carboxylic acids, which therefore act as a probe for the reduced alkoxy chain nanopattern stabilization.

Highly Strained Nanoscale Bicyclophane Monolayers Entering the Third Dimension: A Combined Synthetic and Scanning Tunneling Microscopy Investigation.

Invited for this month's cover are the collaborating groups of Prof. Dr. Sigurd Höger and Dr.

Highly Strained Nanoscale Bicyclophane Monolayers Entering the Third Dimension: A Combined Synthetic and Scanning Tunneling Microscopy Investigation.

Tetrabromo aromatics can be synthesized by the Fischer-Zimmermann condensation of appropriate pyrylium salts with arylene dicarboxylic acid salts. Their cyclization by intramolecular Yamamoto coupling yields strained bicyclophanes with adjustable sizes and different intraannular bridges. All compounds adsorb at the solid/liquid interface on highly oriented pyrolytic graphite (HOPG) and are investigated by scanning tunneling microscopy (STM) with submolecular resolution.

Interplay Between J- and H-Type Coupling in Aggregates of π-Conjugated Polymers: A Single-Molecule Perspective.

Strong dipole-dipole coupling within and between π-conjugated segments shifts electronic transitions, and modifies vibronic coupling and excited-state lifetimes. Since J-type coupling between monomers along the conjugated-polymer (CP) chain and H-type coupling of chromophores between chains of a CP compete, a superposition of the spectral modifications arising from each type of coupling emerges, making the two couplings hard to discern in the ensemble. We introduce a single-molecule H-type aggregate of fixed spacing and variable length of up to 10 nm.

Nanopatterns of arylene-alkynylene squares on graphite: self-sorting and intercalation.

Supramolecular nanopatterns of arylene-alkynylene squares with side chains of different lengths are investigated by scanning tunneling microscopy at the solid/liquid interface of highly oriented pyrolytic graphite and 1,2,4-trichlorobenzene. Self-sorting leads to the intermolecular interdigitation of alkoxy side chains of identical length. Voids inside and between the squares are occupied by intercalated solvent molecules, which numbers depend on the sizes and shapes of the nanopores.

Donor-acceptor interactions between cyclic trinuclear pyridinate gold(i)-complexes and electron-poor guests: nature and energetics of guest-binding and templating on graphite.

Donor-acceptor-type interactions between π-electron systems are of high relevance in the design of chemical sensors. Due to their electron-rich nature, cyclic trinuclear complexes (CTCs) of gold(i) are ideal receptor sites for electron-deficient aromatic analytes. Scanning tunneling microscopy provided insight into the structures of two-dimensional crystals of pyridinate gold CTCs that form on a graphite template at the solid/liquid interface.

Molecular Polygons Probe the Role of Intramolecular Strain in the Photophysics of π-Conjugated Chromophores.

π-Conjugated segments, chromophores, are the electronically active units of polymer materials used in organic electronics. To elucidate the effect of the bending of these linear moieties on elementary electronic properties, such as luminescence color and radiative rate, we introduce a series of molecular polygons. The π-system in these molecules becomes so distorted in bichromophores (digons) that these absorb and emit light of arbitrary polarization: any part of the chain absorbs and emits radiation with equal probability.