Switching-On Fluorescence by Copper (II) and Basic Anions: A Case Study with a Pyrene-Functionalized Squaramide.

Area of Science:

• Supramolecular Chemistry
• Analytical Chemistry
• Materials Science

Background:

• Squaramide derivatives are versatile building blocks in supramolecular chemistry.
• Pyrene moieties are known for their fluorescent properties, useful in sensing applications.
• Selective anion and metal ion detection remains a critical challenge in analytical chemistry.

Purpose of the Study:

• To design and synthesize a novel pyrene-functionalized squaramide receptor.
• To investigate the selective binding and sensing capabilities of the receptor for anions and metal ions.
• To explore the photophysical properties and potential applications of the receptor and its complexes.

Main Methods:

• Synthesis of N,N'-bis(1-pyrenyl) squaramide.
• Spectroscopic studies (UV-Vis absorption, fluorescence spectroscopy) in solution and solid state.
• Complexation studies with various anions (Cl-, OH-, CN-, F-) and metal ions (Cu2+).

Main Results:

• The squaramide receptor selectively binds chloride ions in solution and solid states.
• The receptor selectively detects Cu2+ in acetonitrile, forming a 2:1 complex with intense green fluorescence visible to the naked eye.
• The Cu2+-receptor complex retains fluorescence in the presence of Cl- but undergoes deprotonation and emission changes upon addition of basic anions (OH-, CN-, F-).

Conclusions:

• The designed pyrene-functionalized squaramide is an effective chemosensor for Cl- and Cu2+.
• The receptor exhibits distinct responses to different analytes, enabling selective detection.
• The study highlights the potential of squaramide-based systems for developing advanced fluorescent sensors.