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Ag(I) induced emission with azines having donor-acceptor-donor chromophore
Debdas Ray1, E Siva Subramaniam Iyer, Kalyan K Sadhu
1Department of Chemistry, Indian Institute of Technology, Kanpur, 208016, India.
Two novel azine molecules exhibit weak fluorescence, but strongly emit upon binding with silver ions (Ag+). This selective fluorescence enhancement allows for the sensitive detection of silver ions, even in the presence of other metal ions.
Area of Science:
- Coordination Chemistry
- Materials Science
- Analytical Chemistry
Background:
- Schiff base condensation is a common method for synthesizing ligands.
- Intra-ligand charge transfer (ILCT) can influence the photophysical properties of organic molecules.
- Metal ion sensing often relies on changes in fluorescence intensity or wavelength.
Purpose of the Study:
- To synthesize and characterize two novel azine ligands.
- To investigate the photophysical properties of these ligands and their complexes with metal ions.
- To develop a selective and sensitive method for detecting silver ions.
Main Methods:
- Synthesis of azine ligands via Schiff base condensation.
- Spectroscopic analysis (absorption and emission) in solution and solid-state.
- X-ray crystallography for structural characterization of metal complexes.
- Time-resolved fluorescence measurements.
Main Results:
- Two azine ligands, [3-{4-(dimethylamino)phenyl}prop-2-en-1-ylidene]hydrazone (HL) and [4-(dimethylamino)benzylidene]hydrazone (LL), were synthesized.
- Both ligands exhibit weak fluorescence, attributed to ILCT.
- Upon addition of silver ions (Ag+), a significant (approx. 400-fold) fluorescence enhancement was observed due to metal-ligand binding.
- Copper ions (Cu+) showed a slight emission enhancement, while other tested metal ions did not induce emission.
- Ag+ complexes displayed similar solid-state and solution spectra.
- Time-resolved fluorescence revealed two excited-state lifetimes for the Ag+ complexes.
Conclusions:
- The synthesized azine ligands are effective fluorescent probes for silver ions.
- The selective fluorescence enhancement by Ag+ allows for its detection in the presence of other metal ions.
- The structural and photophysical properties of the Ag+ complexes are well-defined.
- These findings open avenues for developing new chemosensors for metal ion detection.
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