A Chiral [3]Rotaxane Comprising Achiral Bis-macrocyclic and Dumbbell-Shaped Components

A Dualistic Arrangement of a Chiral [1]Rotaxane Based on the Assembly of Two Rings and Two Rods

We demonstrate the synthesis and chiroptical properties of doubled molecules of a chiral [1]rotaxane, based on the assembly of an achiral ring of a phenylacetylene macrocycle (6PAM) and a p-phenylene ethynylene rod. Two molecules of [1]rotaxane constituted the doubled molecule through the ring fusion of 6PAMs to a 10PAM, which assured stationary occupation relative to each optically active unit. The absorption properties of the 10PAM-based doubled molecule and 6PAM-based original unit were consistently characterized by the independent existence of m-phenylene ethynylene ring(s) and p-phenylene ethynylene rod(s). Thus, molar circular dichroism (CD) was directly compared between the doubled molecule (n = 2) and the original unit (n = 1) to show that molar CD was increased more than expected by an increase in the number of units, or by an increase in absorbance. Due to the invariance of the configuration and the relative occupation of two units arranged adjacent to each other in 10PAM, one more comparison was available with an isomeric molecule of two rings and two rods in a threaded-and-unthreaded form. The additional arrangement of an optically inactive unit in an unthreaded form also led to an increase in molar CD, compared to that of the original chiral unit in a threaded form.

Synthesis of a Mechanically Planar Chiral and Axially Chiral [2]Rotaxane

In this study, we synthesized a [2]rotaxane that was both mechanically planar chiral and axially chiral, comprising a symmetrical bis-crown ether featuring a biphenyl moiety (as the macrocyclic component) and a symmetrical bis-ammonium salt (as the dumbbell-shaped component).

Mechanically Interlocked Chiral Self-Templated [2]Catenanes from 2,6-Bis(1,2,3-triazol-4-yl)pyridine (btp) Ligands

We report the efficient self-templated formation of optically active 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) derived homocircuit [2]catenane enantiomers. This represents the first example of the enantiopure formation of chiral btp homocircuit [2]catenanes from starting materials consisting of a classical chiral element; X-ray diffraction crystallography enabled the structural characterization of the [2]catenane. The self-assembly reaction was monitored closely in solution facilitating the characterization of the pseudo-rotaxane reaction intermediate prior to mechanically interlocking the pre-organised system via ring-closing metathesis.