Threading the Needle: Fluorescent Poly-pseudo-rotaxanes for Size-Exclusion Sensing
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Author(s)
Evans, Rachel C.
Belger, Christian
Fox, Niamh Denise Willis
Fennell, John Francis
Swager, Timothy M
Date Issued
April 2016
Journal
Chemistry of Materials
Publisher
American Chemical Society (ACS)
Citation
Willis-Fox, Niamh et al. “Threading the Needle: Fluorescent Poly- Pseudo -Rotaxanes for Size-Exclusion Sensing.” Chemistry of Materials 28.8 (2016): 2685–2691.
Version
Author's final manuscript
Abstract
Poly-pseudo-rotaxanes have been formed through the threading of cucurbit[n]urils (CB[n]) onto the cationic electron-poor poly(pyridyl vinylene), PPyV. The threading of CB[n] onto the PPyV backbone is confirmed by a broadening and upfield shift in the PPyV 1H NMR signals. Encapsulation of PPyV within the CB[n] macrocycles produces dramatic fluorescence enhancements with improved solubility. The threading ability of the CB[n] on the PPyV backbone is governed by the dimensions of the particular CB[n] portal, which grows with increasing number of methylene-bridged glycoluril repeat units. CB[5] is too small to thread onto the PPyV backbone. The portal of CB[6] requires extra time, suggesting high preorganization and/or macrocycle deformation are required to thread onto PPyV. Alternatively, the portal of CB[8] appears to be large enough such that it does not have sufficiently large dipole–dipole interactions with the PPyV chain to promote a strong threading equilibrium. However, we find that the portal of CB[7] is optimal for the threading of PPyV. The PPyV-CB[n] system was further exploited to demonstrate a dual-action sensor platform, combining the PL-responsive behavior demonstrated by PPyV toward electron-rich analytes with the size-exclusion properties imparted by volume of the respective CB[n] cavities. Thin films of PPyV-CB[7] were found to display reversible photoluminescence quenching when exposed to vapors of the biologically relevant molecule indole, which is recovered under ambient conditions, suggesting prospects for new size-exclusion based selective sensory schemes for volatile electron-rich analytes.
MIT Department
Massachusetts Institute of Technology. Institute for Soldier Nanotechnologies
Massachusetts Institute of Technology. Department of Chemistry
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DOI of Published Version
https://doi.org/10.1021/acs.chemmater.6b00186
