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Rotaxane Formation With Intramolecular Charge Transfer Properties for Phosphate Sensing
Chi-Hin Wong1, Daniel Nnaemaka Tritton1, Chak-Shing Kwan1,2
1Department of Chemistry, Hong Kong Baptist University, Hong Kong SAR, the People's Republic of China.
Chemistry, an Asian Journal
|December 7, 2025
Summary
This study introduces a novel rotaxane sensor for detecting anions. The developed mechanically interlocked molecule (MIM) shows significant fluorescence quenching in the presence of phosphate, enabling sensitive anion detection.
Area of Science:
- Supramolecular Chemistry
- Chemical Sensing
- Materials Science
Background:
- Mechanically interlocked molecules (MIMs), particularly rotaxanes, are valuable sensing materials due to their unique structures.
- Intramolecular charge transfer (ICT) in aromatic amides has been used for sensing, but less explored in rotaxanes for anion detection.
Purpose of the Study:
- To construct a novel, kinetically stable [1]rotaxane for anion sensing.
- To investigate the fluorescence response of the rotaxane to various analytes.
Main Methods:
- Synthesis of a [1]rotaxane using a template-directed "slippage" approach.
- Characterization of the rotaxane's fluorescence properties.
- Titration experiments with metal cations and inorganic anions.
Main Results:
- The synthesized [1]rotaxane, 1-H(Rot)·PF6, exhibited restored fluorescence compared to its linear precursor due to inhibited ICT.
- The rotaxane showed marginal fluorescence quenching with metal cations via a photoinduced electron transfer (PeT) mechanism.
- Significant emission quenching (up to 50%) was observed with inorganic anions, particularly phosphate (PO4^3-).
Conclusions:
- The novel rotaxane functions as an effective fluorescent sensor for inorganic anions.
- Phosphate ions can be detected with high sensitivity by this rotaxane system.
- The study highlights the potential of rotaxanes in anion sensing applications.
