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New tetralactam hosts for squaraine dyes
Janel M Dempsey1, Qi-Wei Zhang, Allen G Oliver
1Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA. smith.115@nd.edu.
Organic & Biomolecular Chemistry
|November 13, 2018
Summary
Researchers improved deep-red fluorescent dye properties using tetralactam macrocycles. Two macrocycles effectively bound the dye, enhancing fluorescence, while one sterically hindered binding, showing potential for biological imaging.
Area of Science:
- Supramolecular Chemistry
- Organic Dyes
- Photophysics
Background:
- Squaraine dyes are valuable for their deep-red fluorescence but often suffer from aggregation-caused quenching.
- Macrocyclic compounds offer potential for host-guest chemistry, enabling control over dye properties.
Purpose of the Study:
- To synthesize and characterize novel tetralactam macrocycles with varying substituents.
- To investigate the encapsulation of a deep-red fluorescent squaraine dye within these macrocycles.
- To evaluate the impact of macrocycle encapsulation on the squaraine dye's photophysical properties.
Main Methods:
- Synthesis of three tetralactam macrocycles with methyl, methoxy, and methylenedioxy substituents.
- Experimental determination of squaraine dye encapsulation using UV-Vis absorption, fluorescence spectroscopy, and Nuclear Magnetic Resonance (NMR) spectroscopy in chloroform.
- X-ray crystallography to elucidate the structural basis of squaraine-macrocycle interactions.
Main Results:
- Two tetralactam macrocycles demonstrated strong binding affinity (association constants ~10^6 M^-1) for the squaraine dye.
- One macrocycle, due to steric hindrance from its substituents, showed no affinity for the squaraine dye.
- Encapsulation by one effective macrocycle enhanced the squaraine dye's fluorescence quantum yield, while the other led to fluorescence quenching.
Conclusions:
- Tetralactam macrocycles can be designed to modulate the photophysical properties of squaraine dyes.
- The substituents on the macrocycle play a critical role in determining binding affinity and the resulting fluorescence modulation.
- These tailored squaraine-binding systems hold promise for advanced applications in biological imaging and diagnostics.
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