Diaminomaleonitrile-based Fluorophores as Highly Selective Sensing Platform for Cu²

Area of Science:

• Analytical Chemistry
• Materials Science
• Environmental Science

Background:

• Accurate detection of metal ions like copper (Cu²⁺) is crucial for environmental monitoring and biological studies.
• Existing chemosensors often rely on metal-complexation induced fluorescence enhancement, necessitating exploration of alternative sensing mechanisms.
• Diaminomaleonitrile-based compounds offer potential as versatile building blocks for chemosensor development.

Purpose of the Study:

• To synthesize and characterize a novel colorimetric and fluorescent chemodosimeter for selective Cu²⁺ detection.
• To investigate the sensing mechanism of the developed probe, differentiating it from conventional metal-complexation based methods.
• To evaluate the probe's sensitivity, selectivity, and detection limit for Cu²⁺ in solution.

Main Methods:

• Synthesis of a diaminomaleonitrile-based chemodosimeter (probe 1).
• Spectroscopic analysis (UV-Vis absorption and fluorescence emission) for Cu²⁺ detection.
• Nuclear Magnetic Resonance (¹H NMR, ¹³C NMR) and mass spectrometry to elucidate the sensing mechanism.
• Selectivity studies against various interfering metal ions.
• Determination of the detection limit for Cu²⁺.

Main Results:

• Probe 1 exhibited high selectivity and sensitivity towards Cu²⁺.
• Upon addition of Cu²⁺, a 30-nm blue shift in absorption at 530 nm and significant fluorescence enhancement were observed.
• The detection limit for Cu²⁺ was determined to be as low as 28 nM.
• Spectroscopic analysis confirmed a Cu²⁺-promoted hydrolysis reaction as the sensing mechanism, distinct from metal-complexation.
• Further studies with probe 2 validated the universality of this hydrolysis-based sensing mechanism.

Conclusions:

• A novel diaminomaleonitrile-based chemodosimeter enables sensitive and selective colorimetric and fluorescent detection of Cu²⁺.
• The unique Cu²⁺-promoted hydrolysis mechanism offers a new strategy for designing metal ion sensors.
• The developed probe demonstrates significant potential for practical applications in Cu²⁺ monitoring.