Cyclobis(Paraquat‐4,4′‐Biphenylene)–an Organic Molecular Square

Publisher Website
Google Scholar
Abstract
Template‐directed syntheses of cyclobis(paraquat‐4,4′‐biphenylene) (1)– a Molecular square–have been achieved by use of π‐electron‐rich macrocyclic hydroquinone‐based and acyclic ferrocene‐based templates. In particular, the use of a polyether‐disubstituted ferrocene derivative as a template permits synthesis of 1 (which is accessible only in very low yields without templates) on a preparative scale. Furthermore, the use of a macrocyclic hydroquinone‐based polyether template in corporating an ester function in one polyether chain–an (oriented) macrocycle–affords a 1 : 1 mixture of two topologically stereoisomeric [3]catenanes. Ester hydrolysis of the π‐electron‐rich macrocyclic components mechanically interlocked with 1 within the catenated structures releases the tetracationic cyclophane in quantitative yield as a result of the degradation of the [3]catenanes. The molecular square has been characterized by X‐ray crystallography, FAB mass spectrometry, 1H NMR and 13C NMR spectroscopies, and elemental analysis. The binding properties of 1 and of the smaller cyclophane cyclobis(paraquat‐p‐phenylene) toward a series of π‐electronrich guests have also been investigated with the above techniques and UV/VIS spectroscopy. The self‐assembly of the resulting supramolecular complexes in solution and in the solid state is driven mainly by π–π stacking interactions and hydrogen‐bonding interactions, as well as by edge‐to‐face T‐type interactions. In particular, the complexation of ferrocene or a ferrocene‐based derivative within the cavity of 1 suggests the possibility of constructing functioning ferrocene‐based molecular and supramolecular devices that can be controlled electrochemically in the form of catenanes, rotaxanes, and pseudorotaxanes.

This publication has 120 references indexed in Scilit: