Theoretical Study of a Coumarin-Based Colorimetric Sensor for Cu2+ Detection Using DFT Calculation
DOI:
https://doi.org/10.61326/jaasci.v4i1-2.433Keywords:
Chemosensor, Colorimetric detection, Coumarin, Cu2+ ion, TD-DFTAbstract
The development of chemosensors for the detection of metal ions that are environmentally and biologically significant remains an important research goal. Herein, we present the rational design of a novel coumarin derivative, (E)-6-((1H-pyrrol-2-yl)diazenyl)-7-hydroxy-2H-chromen-2-one (CTD), as a potential colorimetric chemosensor for Cu2+ ions. Theoretical studies were conducted using DFT and TD-DFT methods to elucidate the electronic and optical properties of the 1:1 stoichiometric complex molecule formed between CTD and Cu2+. Ground-state geometry optimizations performed with the PBEPBE function and the LANL2DZ basis set revealed that CTD is an effective chelating agent for Cu2+. The absorption maximum of CTD was 410.81 nm as a result of TD-DFT calculations. Following complexation with Cu2+, a significant bathochromic shift of approximately 90 nm was observed, and the absorption of the CTD-Cu2+ complex was calculated to be 502.10 nm. This pronounced red shift is indicative of a visible colorimetric response. To reveal the electronic origin of this spectral modulation, a Frontier Molecular Orbital (FMO) analysis was performed. The calculations showed a decrease in the HOMO-LUMO energy gap (Egap) from 1.78 eV for the free CTD molecule to 1.54 eV for the CTD-Cu2+ complex. These theoretical findings strongly suggest that CTD is a highly promising candidate for experimental validation as a new generation, visually detectable colorimetric chemosensor for Cu2+.
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