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DFT and TDDFT studies on π-conjugated ligands for copper sensing: analyzing electronic structures and optical
Susheel1, Abdullah Saad Alsubaie2, Mukhtar Ahmed1
1Department of Chemistry, Central University of Haryana, Mahendergarh, Haryana, 123031, India.
Journal of Molecular Modeling
|October 22, 2025
Summary
Density functional theory investigated quinoline-based ligands and copper complexes, revealing L3-Cu²⁺ as promising for metal ion sensors due to its stability and optical properties. This theoretical study supports experimental findings for copper ion detection.
Area of Science:
- Computational Chemistry
- Materials Science
- Spectroscopy
Background:
- Investigated structural, bonding, and optical properties of π-conjugated quinoline-based ligands (L1-L4) and their copper (Cu²⁺) complexes.
- Utilized density functional theory (DFT) and time-dependent DFT (TDDFT) for comprehensive analysis.
Purpose of the Study:
- To explore the potential of quinoline-based ligands and their copper complexes for applications in metal ion sensing.
- To elucidate the electronic structure, bonding characteristics, and optical behavior of these systems.
Main Methods:
- Employed DFT for geometry optimization and frequency analysis (B3LYP/6-311G(d,p) for non-metals, LANL2DZ for copper).
- Utilized the polarized continuum model for solvation.
- Applied Natural Bond Orbital (NBO) analysis for bonding nature and stabilization energies.
- Simulated absorption spectra using TDDFT (ORCA4.2) and performed topological analysis (Multiwfn, VMD).
Main Results:
- L3 ligand exhibited the lowest HOMO-LUMO gap (3.05 eV), significantly reduced in its Cu²⁺ complex (2.52 eV), indicating enhanced charge transfer.
- NBO analysis showed high stabilization energy (79.15 kcal/mol) for L3-Cu²⁺, confirming strong donor-acceptor interactions.
- TDDFT revealed strong ligand-to-metal charge transfer bands for L3-Cu²⁺ at 452 and 667 nm.
- Non-linear optical analysis indicated enhanced hyperpolarizability in copper complexes, particularly L1-Cu²⁺ and L4-Cu²⁺.
Conclusions:
- The L3-Cu²⁺ complex demonstrates favorable stability and optical properties, making it a strong candidate for developing selective copper ion sensors.
- Theoretical findings align with experimental observations, validating the potential of L3-based systems for copper ion detection applications.
- The study provides a theoretical framework for designing novel metal ion sensors with improved optical responses.
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