The paper compares the experimental FT-IR, UV-vis, and ¹H NMR spectra of isoconazole and bifonazole with the density functional theory (DFT) calculations using different functionals. The results were compared with previously reported data related to their analogue, posaconazole. The analysis of calculated IR spectra with use of CAM-B3LYP (isoconazole) or B3LYP (bifonazole) functionals shows good accordance with the experimental IR spectrum. The best compatibility between the experimental and theoretical UV spectra was observed with the use of B3LYP or wB97XD functionals for isoconazole or bifonazole, respectively. The reason for the difference in the UV-vis spectra of isoconazole and bifonazole was discussed based on linear response time-dependent DFT and natural bond orbital methods. The calculated ¹H NMR spectrum shows that the DFT formalism, particularly the B3LYP functional, give an accurate description of the isoconazole and bifonazole chemical shifts.

This study presents an integrated experimental and theoretical investigation of two pharmacologically significant neolignans—magnolol and honokiol—with the aim of characterizing their structural and spectroscopic properties in detail. Experimental Fourier-transform infrared (FT-IR), ultraviolet–visible (UV-Vis), and nuclear magnetic resonance (¹H NMR) spectra were recorded and analyzed. To support and interpret these findings, a series of density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were conducted using several hybrid and long-range corrected functionals (B3LYP, CAM-B3LYP, M06X, PW6B95D3, and ωB97XD). Implicit solvation effects were modeled using the CPCM approach across a variety of solvents. The theoretical spectra were systematically compared to experimental data to determine the most reliable computational approaches. Additionally, natural bond orbital (NBO) analysis, molecular electrostatic potential (MEP) mapping, and frontier molecular orbital (FMO) visualization were performed to explore electronic properties and reactivity descriptors. The results provide valuable insight into the structure–spectrum relationships of magnolol and honokiol and establish a computational benchmark for further studies on neolignan analogues.