| Autor: |
Wang Y; Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA . Email: stoddart@northwestern.edu ; Tel: +1-847-491-3793., Sun J; Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA . Email: stoddart@northwestern.edu ; Tel: +1-847-491-3793., Liu Z; Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA . Email: stoddart@northwestern.edu ; Tel: +1-847-491-3793., Nassar MS; Joint Center of Excellence in Integrated Nano-Systems (JCIN) , King Abdul-Aziz City for Science and Technology (KACST) , P. O. Box 6086 , Riyadh 11442 , Saudi Arabia., Botros YY; Joint Center of Excellence in Integrated Nano-Systems (JCIN) , King Abdul-Aziz City for Science and Technology (KACST) , P. O. Box 6086 , Riyadh 11442 , Saudi Arabia.; PanaceaNano, Inc. , 2265 East Foothill Boulevard , Pasadena , California 91107 , USA., Stoddart JF; Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , USA . Email: stoddart@northwestern.edu ; Tel: +1-847-491-3793. |
| Abstrakt: |
Two potential viologen-based molecular lasso precursors-both composed of a 4,4'-bipyridinium (BIPY 2+ ) unit as part of a rope appended to a cyclobis(paraquat- p -phenylene) (CBPQT 4+ ) loop-that have been designed to mimic the threading/unthreading motion of lasso peptides, have been synthesised and characterised. Solution and solid-state experiments reveal that, when the BIPY 2+ unit in the rope and the CBPQT 4+ loop are connected by a bulky linker, no lasso-like conformational transformation is observed between the different redox states on account of steric effects. In sharp contrast, when the linker size is small, the molecule can be switched between (i) a free rope-like conformation in its fully oxidised state and (ii) a self-entangled lasso-like conformation under reducing conditions employing either chemical or electrochemical stimuli: the BIPY˙ + unit in the rope resides inside the cavity of the CBPQT 2( ˙ +) loop, forming a pseudo[1]rotaxane. The switching process is reversible and stereochemically unambiguous. This research shows how tiny structural differences can induce significantly different self-complexing properties and sheds light on designing functional artificial actuators. |
