Structural and Spectroscopic Properties of Magnolol and Honokiol-Experimental and Theoretical Studies.

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 (H 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.