Theoretical investigation of cyromazine tautomerism using density functional theory and Moller–Plesset perturbation theory methods

Authors: TU, YI-SHU - Ministry Of Science And Technology; TSENG, YUFENG - National Taiwan University; Appell, Michael

Submitted to: Molecular Simulation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/24/2018
Publication Date: 8/14/2018
Citation: Tu, Y.-S., Tseng, Y.J., Appell, M. 2018. Theoretical investigation of cyromazine tautomerism using density functional theory and Moller–Plesset perturbation theory methods. Molecular Simulation. 44(16):1344-1352. https://doi.org/10.1080/08927022.2018.1506117.
DOI: https://doi.org/10.1080/08927022.2018.1506117

Interpretive Summary: Pest control is important for commodity production and consumer health. Cyromazine is a pesticide with low toxicity to mammals and birds that is applied for fly control in agricultural production. Determination of cyromazine levels can provide information on exposure and its fate in agricultural processes. Computational methods were developed and applied to identify the chemical properties of cyromazine that are related to detection. The peak characteristics in the calculated infrared and Raman spectra provide structural information on cyromazine and simplify the interpretation of experimental spectra. These findings are important to analytical scientists and regulators looking for economical methods to improve cyromazine detection.

Technical Abstract: A computational chemistry analysis of six unique tautomers of cyromazine, a pesticide used for fly control, was performed with density functional theory (DFT) and canonical second order Moller–Plesset perturbation theory (MP2) methods to gain insight into the contributions of molecular structure to detection properties. Full geometry optimization using the 6-311++G** basis set provided energetic properties, electrostatic charges, frontier orbitals, and vibrational modes. Excitation energies were obtained using time-dependent density functional theory. Hydrogen location and bond order contribute significantly to the electronic properties. The common cyromazine tautomer possesses the lowest electronic energy, highest band gap energy, and highest excitation energy. Tautomerization involving intramolecular hydrogen transfer influences the natural charges of neighboring atoms and the frontier orbital properties. The excitation energies are highly correlated with band gap energies of the frontier orbitals. The calculated infrared and Raman spectra are suitable for vibrational assignments associated with the chemical structure. The tautomeric forms of cyromazine possess similar spatial properties and significant variation in electronic properties.