1,8-naphthyridine-derived Ni(2+)/Cu(2+)-selective fluorescent chemosensor with different charge transfer processses

Area of Science:

• Analytical Chemistry
• Materials Science
• Biophysical Chemistry

Background:

• Developing selective and sensitive chemosensors for metal ion detection is crucial for environmental monitoring and biological studies.
• 1,8-naphthyridine derivatives offer promising photophysical properties for sensing applications.

Purpose of the Study:

• To develop a highly fluorescent chemosensor for selective detection of Ni(2+) and Cu(2+) ions.
• To investigate the sensing mechanism and differentiate between Ni(2+) and Cu(2+) in various environments.

Main Methods:

• Synthesis of a 1,8-naphthyridine-based fluorescent chemosensor.
• Spectroscopic analysis (fluorescence) in aqueous solutions across a wide pH range (4-10).
• Cellular imaging studies and picosecond time-resolved fluorescence spectroscopy.
• Time-dependent density functional theory (TD-DFT) calculations.

Main Results:

• The chemosensor exhibited high sensitivity and selectivity for Ni(2+) and Cu(2+) over other common cations.
• Detection was effective in aqueous solutions (pH 4-10) and within cellular environments.
• Ethylenediamine selectively interacted with the Cu(2+) complex, enabling differentiation between Ni(2+) and Cu(2+).
• Distinct fluorescence on-off mechanisms were elucidated: Ni(2+) involved metal-to-ligand charge transfer, while Cu(2+) involved ligand-to-metal charge transfer.

Conclusions:

• A robust 1,8-naphthyridine-based chemosensor was successfully developed for Ni(2+) and Cu(2+) detection.
• The developed sensor demonstrates applicability in complex biological systems.
• The study provides insights into the photophysical mechanisms underlying metal ion sensing.