Optical Distinction between "Slow" and "Fast" Translational Motion in Degenerate Molecular Shuttles. Issue 22 (1st February 2017)

• Record Type: Journal Article
• Authors: Vukotic, V. Nicholas; Zhu, Kelong; Baggi, Giorgio; Loeb, Stephen J.
• Is Part Of: Angewandte Chemie international edition. Volume 56:Issue 22(2017)
• Page Start: 6136
• Page End: 6141
• Publication Date: 2017-02-01
• Subjects: co-conformations -- molecular shuttles -- optical switches -- rotaxanes -- supramolecular chemistry; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201612549
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: A series of six [2]rotaxane molecular shuttles was designed which contain an axle with a benzo‐bis(imidazole) core (in either a neutral or dicationic form) and a single 24‐membered, crown ether wheel (24C6, B24C6, orDMB24C6 ), and the shuttling rates of the ring along the axle were determined. The charged versions showed much slower shuttling rates as a result of the increase in noncovalent interactions between the axle and wheel. The [2]rotaxane with aB24C6 wheel shows a difference in fluorescence between the charged and neutral species, while the [2]rotaxane with aDMB24C6 wheel exhibits a difference in color between the charged and neutral compounds. These changes in optical properties can be attributed to the structural differences in the co‐conformations of the [2]rotaxane as they adapt to the changes in acid/base chemistry. This allowed the relative rate of the translational motion of a molecular shuttle to be determined by observation of a simple optical probe. Abstract : Set the wheels in motion : The dicationic and neutral forms of a degenerate molecular shuttle containing an axle with a benzo‐bis(imidazole) core show very different shuttling rates as a result of differences in the noncovalent interactions between the axle and wheel in the two forms. Acid/base chemistry can be used to control the shuttling, which is signaled by an optical output: a change in color or fluorescence.