Physico-chemical studies on some fluorescence sensors: DFT based ESIPT process

Area of Science:

• Organic Chemistry
• Photophysics
• Computational Chemistry

Background:

• Schiff bases are versatile organic compounds with diverse applications.
• Intramolecular proton transfer is crucial for understanding photophysical properties.
• Metal ion sensing is an important area in chemical research.

Purpose of the Study:

• To synthesize novel heterocyclic Schiff base derivatives.
• To investigate their excited-state intramolecular proton transfer (ESIPT) processes.
• To explore their interaction with copper(II) ions and their electronic properties.

Main Methods:

• Synthesis and characterization using NMR, mass spectrometry, and CHN analysis.
• Electronic spectral studies to investigate ESIPT.
• Fluorescence spectroscopy to study metal ion interactions.
• Density Functional Theory (DFT) calculations for electronic structure analysis.

Main Results:

• Synthesized novel heterocyclic Schiff bases.
• Confirmed predominance of the trans enol form.
• Observed significant fluorescence quenching upon addition of Cu(2+).
• DFT calculations provided insights into energy, dipole moment, and charge distribution.
• PES calculations showed a high energy barrier for rotamer interconversion in the excited state.
• NLO and NBO analyses indicated specific charge distributions.
• HOMO/LUMO and MEP studies evidenced intramolecular charge transfer (ICT).

Conclusions:

• The synthesized Schiff bases exhibit interesting photophysical properties.
• Their fluorescence can be modulated by copper ions, suggesting potential as sensors.
• Computational studies elucidated the electronic structure and ICT mechanisms within the molecules.