Sensitive Structural Control of Macrocycle Threading by a Fluorescent Squaraine Dye Flanked by Polymer Chains

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Organic Chemistry

Background:

• Macrocyclic compounds offer unique host-guest chemistry.
• Squaraine dyes are known for their optical properties.
• Polyethylene glycol chains can modify solubility and interactions.

Purpose of the Study:

• To synthesize and characterize a novel pseudorotaxane complex.
• To investigate the influence of N-alkyl substituents on squaraine dye threading.
• To evaluate the near-infrared fluorescence properties of the complex.

Main Methods:

• Synthesis of a macrocyclic tetralactam and functionalized squaraine dyes.
• Formation of the pseudorotaxane complex via threading.
• Thermodynamic and kinetic measurements of association.
• Spectroscopic analysis of fluorescence properties.

Main Results:

• A pseudorotaxane complex was successfully formed between tetralactam and squaraine dye.
• Near-infrared fluorescence properties were observed.
• Steric bulk of N-alkyl substituents significantly affected threading kinetics.
• High association constants were maintained despite kinetic variations.

Conclusions:

• The study demonstrates a method for creating fluorescent pseudorotaxanes.
• Substituent engineering of dyes can control complexation dynamics.
• These findings are relevant for developing new fluorescent materials and sensors.