Vol. 24 No. 3 (2025): Mapana Journal of Sciences
Research Articles

Spectrophotometric Investigations of Charge Transfer Complexes formed between imidazoles and DMAD

  • Pratibha Mittal,
  • Manisha Patni,
  • Raakhi Gupta
Pratibha Mittal
Department of Chemistry, IIS (Deemed to be University), Jaipur, 302020, Rajasthan, India
Manisha Patni
Department of Chemistry, IIS (Deemed to be University), Jaipur, 302020, Rajasthan, India
Bio
Raakhi Gupta
Department of Chemistry, IIS (Deemed to be University), Jaipur, 302020, Rajasthan, India
Bio

Published 2025-09-29

Keywords

  • Imidazole,
  • DMAD,
  • UV studies,
  • DFT studies,
  • Global reactivity descriptiors,
  • FMO analysis
    • ...More
    Less

Copyright (c) 2025

Creative Commons License

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Abstract

Four novel charge transfer (CT) complexes were synthesized between imidazole-based donors and dimethyl acetylenedicarboxylate (DMAD) as the electron acceptor at room temperature in dichloromethane and acetone. CT complex formation was confirmed by characteristic n → π* and π → π* electronic transitions in UV-Vis spectra. Stoichiometric analysis using Job's method revealed 1:1 and 2:1 donor–acceptor ratios for imidazole and N-methylimidazole, respectively. Among the synthesized complexes, those containing N-methylimidazole displayed higher stability constants, negative Gibbs free energy changes (ΔG⁰), and molar extinction coefficients (ε), reflecting spontaneous as well as stable complexation. Additionally, the lowest CT transition energies (ECT) in dichloromethane confirmed stronger donor–acceptor interactions in the less polar solvent. DFT calculations at the B3LYP/6-31+G(d) level were carried out to further validate donor strength. N-methylimidazole exhibited the greater HOMO energy, low HOMO–LUMO energy gap (ΔE) and the most favourable global reactivity descriptors—chemical softness and chemical potential—affirming its better electron-donating ability compared to imidazole.

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