| New atropisomers have been synthesized that display restricted rotation about a Caryl-Nimide bond to afford two conformers: a convergent syn- and a divergent anti-isomer. These molecules interconvert with one another at elevated temperatures, but are both stable and separable at ambient temperatures.; The short-term goal is to thoroughly synthesize and study the properties of these atropisomers at the molecular level. Although the syntheses were quite straightforward, the properties of these molecules were found to be quite remarkable. Various experiments were carried out that exploited the differences in polarity, size, and molecular recognition between the two isomers. Another area of research with these molecules is to utilize their inherent preorganization to form macrocycles. More specifically, a convergent syndialkyne has been used to form a large shape-persistent 48-membered macrocycle with the ability to shape-adapt into three conformers. Furthermore, techniques to control the equilibrium of these isomers and to later incorporate them into more extended arrays have been developed. One particularly effective method is the use of host-guest chemistry, such as metal ions, to quantitatively favor a syn-bis(pyridine) ligand as shown below.; The long-term goal of this project is to synthesize switchable polymeric materials from these atropisomeric monomers. The shape of these materials is governed by controlling the monomeric syn/anti -ratio. Several resulting shape-based properties that can potentially be modulated are viscosity, refractive index, conductivity, mechanical properties, and polymer morphology. Some of the more interesting potential applications of these systems are switches, sensors, reprogrammable polymers, and memory devices for information storage. |
