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Updated: Jun 8, 2025
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On-line Analysis of Nitrogen Containing Compounds in Complex Hydrocarbon Matrixes
Published on: August 5, 2016
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NEXAFS Spectra Simulations of Nitrogen-Bearing Heterocycles.
Ricardo R Oliveira1, Amanda D Torres1, Alexandre B Rocha1
1Chemistry Institute, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil - 21941-909.
ACS Omega
|November 4, 2024
Summary
Simulating K-edge NEXAFS spectra using time-dependent density functional theory (TDDFT) and inner-shell multiconfigurational self-consistent field (IS-MCSCF) accurately characterizes nitrogen-containing heterocycles. These computational methods align well with experimental data for biomolecule building blocks.
Area of Science:
- Computational chemistry
- Spectroscopy
- Materials science
Background:
- Five-membered nitrogen-containing heterocycles are crucial biomolecule components with diverse technological applications.
- Accurate characterization techniques are essential for understanding these important molecular systems.
Purpose of the Study:
- To simulate K-edge NEXAFS spectra of selected nitrogen-containing heterocyclic molecules.
- To evaluate the applicability of time-dependent density functional theory (TDDFT) and inner-shell multiconfigurational self-consistent field (IS-MCSCF) methods for spectral characterization.
- To investigate the impact of vibronic coupling on TDDFT calculations.
Main Methods:
- Simulations of K-edge NEXAFS spectra were performed using TDDFT and IS-MCSCF.
- Vibronic coupling was incorporated into the TDDFT computations.
- Molecular orbital binding energies and transition energies were compared.
Main Results:
- A discrepancy was observed between molecular orbital binding energies and transition energies from IS-MCSCF, suggesting limitations of the orbital picture for NEXAFS.
- TDDFT and IS-MCSCF results showed good agreement with each other and with experimental data.
- Vibronic coupling and vertical transition results were found to be highly similar.
Conclusions:
- TDDFT and IS-MCSCF are reliable computational methods for characterizing K-edge NEXAFS spectra of nitrogen-containing heterocycles.
- The IS-MCSCF method was successfully applied to relatively large molecular systems for the first time.
- Computational simulations provide valuable insights complementing experimental observations in molecular characterization.
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