Premium
A Photoswitchable Rotaxane with a Folded Molecular Thread
Author(s) -
Abraham Werner,
Grubert Lutz,
Grummt Ulrich W.,
Buck Karin
Publication year - 2004
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200400243
Subject(s) - rotaxane , cyclophane , chemistry , cycloheptatriene , molecular switch , molecular machine , polymer chemistry , stereochemistry , crystallography , supramolecular chemistry , molecule , nanotechnology , crystal structure , organic chemistry , materials science
Novel [2]rotaxanes containing the tetracationic cyclophane cyclobis(paraquat‐4,4‐biphenylene) and a dumbbell‐shaped molecular thread incorporating a photoactive diarylcycloheptatriene station as well as a photoinactive anisol station have been synthesized with yields of nearly 50 % by the alkylative endcapping method. The rotaxane was transformed into the related rotaxane incorporating a diaryl tropylium unit by electrochemical oxidation. The precursor of the cycloheptatrienyl rotaxane, the related pseudorotaxane, and the rotaxanes incorporating the diarylcycloheptatriene and the corresponding tropylium unit were characterized by 1 HNMR spectroscopy and UV/Vis spectroscopy. According to the NMR spectra, both the cycloheptatriene and the tropylium rotaxane possess a folded conformation enabling the tetracationic cyclophane to interact with two stations. The diarylcycloheptatriene station is incorporated inside the cavity of the cyclophane and the anisol station resides alongside the bipyridinium unit of the cyclophane. In contrast, the anisol station is inside the cyclophane in the tropylium rotaxane. The exchange between both conformations can be achieved by introducing the methoxy leaving group into the cycloheptatriene ring; the tropylium rotaxane is generated by photoheterolysis of this methoxy‐substituted rotaxane, which reacts thermally back to the cycloheptatriene rotaxane, thus closing the switching cycle. These induced conformational changes achieve a so‐called molecular machine.