DFT-based investigation on dihydrodehydrodiconiferyl-9-O-sulfate in methanol: insights into spectroscopy (IR, Raman, and NMR), reactivity, and topology analyses

The electronic structure and spectroscopic properties of dihydrodehydrodiconiferyl-9-O-sulfate alcohol (DDDC-9-OS), a phenolic neolignan sulfate in methanolic solution were investigated using density functional theory (DFT). An extensive benchmark of functionals, including B3LYP, B3LYP-D3BJ, PW6B95, PW6B95D, ωB97X-D, MPWPKZB, and LC-TPSSTPSS, combined with the 6-311++G(d,p) and cc-pVTZ basis sets, was performed to simulate nuclear magnetic resonance (NMR) chemical shifts and vibrational (IR and Raman) spectra. With mean variances less than 4%, the calculated harmonic frequencies showed excellent agreement with experimental infrared data. While the B3LYP/6-311++G(d,p) level theory offered the closest match to experimental IR band intensities, chemical shift predictions from the CSGT/ωB97X-D/6-311++G(d,p) method shown good agreement with experimental NMR values. The intramolecular charge distribution, reactivity, and non-covalent interactions controlling the stability of the molecule were also profoundly revealed by a thorough examination of the electronic structure using the B3LYP-D3BJ/6-311++G(d,p) level, which included the electron localization function (ELF), frontier molecular orbitals (FMO), reduced density gradient non-covalent interactions (RDG-NCI), and molecular electrostatic potential (MEP).