Star-Shaped Oligo(p-phenylenevinylene) Substituted Hexaarylbenzene:  Purity, Stability, and Chiral Self-assembly^†

Abstract

An oligo(p-phenylenevinylene) (OPV)-substituted hexaarylbenzene has been synthesized and fully characterized. Recycling gel permeation chromatography appeared to be a powerful technique to obtain the OPV molecules in a very pure form. X-ray analysis and polarization optical microscopy revealed that the OPV molecule is plastic crystalline at room temperature with an ordered columnar superstructure. In apolar solvents, the molecules self-assemble via a highly cooperative fashion into right-handed chiral superstructures, which are stable even at high temperatures and low concentration. Atomic force microscopy revealed right-handed fibers with a diameter of 6 nm, indicating pi-stacked aggregates; on a silicon oxide substrate, supercoiled chiral structures were observed. STM studies on a liquid-solid interface showed that the star-shaped OPV molecule forms an organized monolayer having a chiral hexagonal lattice.

What Molecular Features Govern the Mechanism of Supramolecular Polymerization?

“…The molecule self-assembles to chiral, ordered stacks in a highly cooperative manner (Figure 6 A), as indicated by the cooperativity parameter of s = 10 À4 . [48] The precise reason for cooperativity in these last two examples is unclear (from a molecular point of view) as they lack an apparent intermolecular hydrogen bond but still exhibit high cooperativity. In another example, self-assembly of an OPVsubstituted hexarylbenzene (15, Figure 6) led to the formation of ordered, columnar superstructures.…”

Dynamics in Self-assembled Organic Monolayers at the Liquid/Solid Interface Revealed by Scanning Tunneling Microscopy

“…3A) that acts as molecular 'hexapod' in a self-assembled monolayer at the 1-phenyloctane/ HOPG interface. [52][53][54] Structurally defect-free 2D crystalline domains covering large areas are not observed though often 'disordered' domains are observed in the midst of or between these small crystalline domains. We identify a group of molecules as belonging to a disordered domain if the centres of the molecules are not on top of 2D crystalline lattice points within a given area or if the molecules have a different orientation than those in the crystalline matrix.…”

Star-Shaped Conjugated Systems

“…For example, they were employed to design new ligands for multimetal complexes [131,230,231,232,233,234]. Especially the cobalt complexes, were subsequently used to prepare carbon nanomaterials by pyrolysis [235].…”