Synthesis, Aggregation, and Adsorption Phenomena of Shape-Persistent Macrocycles with Extraannular Polyalkyl Substituents

Abstract

The synthesis of shape-persistent macrocycles based on the phenyl-ethynyl backbone containing various extraannular alkyl side chains is described. Although compound solubility increases with increasing size of the side groups, decreasing the solvent polarity induces aggregation of the rings by nonspecific interactions. This was investigated by proton NMR spectroscopy. The magnitude of aggregation can be varied by using solvent mixtures of different hexane content, supporting the model of a solvophobic effect. From 1,2,4-trichlorobenzene solution the macrocycle 1c adsorbs at the surface of highly oriented pyrolitic graphite (HOPG). The two-dimensional order of the structure was investigated by scanning tunneling microscopy (STM) revealing the formation of a two-dimensional lattice of p1(2)mm symmetry with lattice parameters A = 3.6 nm, B = 5.7 nm, and Gamma = 74 degrees.

Shape‐Switchable Azo‐Macrocycles

“…Shape persistent macrocycles comprising similar polyalkyl substituents have already been reported by Höger et al. [104][106][184] [196]- [198] Increased adsorption properties of these macrocycles with an increasing number of alkyl chains were observed. The driving force for the adsorption of the macrocycles at the surface is the nonspecific attractive van der Waals (vdW) interaction of the rigid and the flexible ring parts, including the alkyl chains, with the graphite surface.…”

“…[105] Scheme 9 Retrosynthetic scheme for the synthesis of symmetric macrocycles 2. In the case of the asymmetric macrocycle 4, the coupling between a nitroso-and an amino-functionalized semicircle (Mills reaction) [32] might be more favorable in order to enable the coupling of two different precursors (pathway a in Scheme 11).…”

Self-assembling subnanometer pores with unusual mass-transport properties

“…To date, several classes of planar, rigid macrocycles have been reported, including those based on arylene ethynylene backbones 21,22 and recently reported ones with aryl amide and hydrazide 23 or Schiff base 24 backbones that can be efficiently prepared. With their persistent shapes unaffected by synthetic modifications, these macrocycles provide an attractive class of building blocks for forming nanotubular assemblies containing internal pores of defined diameters.…”

Optical switching studies of an azobenzene rigidly linked to a hexa-peri-hexabenzocoronene derivative in solution and at a solid–liquid interface

“…Porous molecular monolayers are used as two-dimensional hosts for molecular guests, which may be employed for molecular selection or the isolation of single molecules. They have been obtained from macrocycles at the interface between an organic solution and the basal plane of graphite, providing pores in the range of 1.2 to 2.7 nm [19][20][21][22][23]. Alternatively, supramolecular two-dimensional structures have been self-assembled at such solid-liquid interfaces, which are stabilized van der Waals interactions between pending alkyl chains [11,[24][25][26][27][28].…”