Determination of the molecular structure and spectroscopic properties of capsaicin. (July 2023)

• Record Type: Journal Article
• Authors: Çınar, Mehmet; Alım, Bünyamin; Alım, Zuhal; Şakar, Erdem
• Is Part Of: Radiation physics and chemistry. Volume 208(2023)
• Publication Date: 2023-07
• Subjects: Capsaicin -- Density functional theory -- Spectroscopic characterization -- Hirshfeld surface -- Density of states; Radiation chemistry -- Periodicals; Radiometry -- Periodicals; Radiation -- Periodicals; Chimie sous rayonnement -- Périodiques; 539.2
• DOI: 10.1016/j.radphyschem.2023.110879
• Languages: English
• ISSNs: 0969-806X

Abstract

Abstract: In this study, the ground state molecular structure and spectroscopic features of cis- and trans-forms of capsaicin were investigated using DFT (B3LYP) invoking 6–311++G(d, p) basis set. The optimized geometry of capsaicin was determined for the isolated molecule in a vacuum, and then the vibrational spectra –IR and Raman-were obtained, and the assignments of fundamental vibrational modes were done. By applying the GIAO method, proton and carbon chemical shifts were computed for the gas and solvated phases. Besides using the TD-DFT, the Hirshfeld surface and Molecular Electrostatic Potential surfaces were obtained and evaluated to understand the electronic properties. The Total and partial density of state (TDOS and PDOS) spectra were also examined. All obtained computational results were compared with the previously reported experimental data. A high accuracy was obtained for the ground state geometrical structure, and thus, the vibrational frequencies especially lie on the finger print region are predicted also with a high correlation. Similarly, the optimization of chemical shift values calculated by considering solvent effects with experimental data were found as high R 2 values of 0.9953 and 0.9455 for C and H atoms, respectively. This comparison shows that the DFT method precisely predicts capsaicin's molecular and spectroscopic characteristics. Highlights: The vibrational, NMR and electronic analyzes of capsaicin were performed in detail. A strong correlation was found between the experimental and DFT calculations. The most significant differences were observed in dihedral angles. The HOMO and LUMO energies of cis-capsaicin were obtained as −5.86 eV and −0.51 eV.