Upon DFT-D3 dispersion correction and ECD spectral confirmation, only several conformers can stably coexist for three fungal cycloaspeptides (A, D, G)

• Published in: Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy Vol. 283; p. 121710
• Main Authors: Liu, Yong, Liu, Cai-Ping, Mang, Chao-Yong, Wu, Ke-Chen
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2022
• Subjects: Conformation; Density functional calculations; Dispersion correction; Electronic circular dichroism; Molecular orbital; Solvation effect; Molecular orbital; Density functional calculations; Dispersion correction; Electronic circular dichroism; Solvation effect; Conformation
• ISSN: 1386-1425
• DOI: 10.1016/j.saa.2022.121710

[Display omitted] •Few conformers can co-exist.•TD-B3LYP-D3 can more successfully reproduce the experiment than TD-CAM-B3LYP-D3.•ECD bands observed in experiment originate from the ππ* transitions other than the σπ* transitions.•Excitation energy and Cotton effect are seriously influenced by component of the Hartee-Fock wavefunctions of hybrid density functionals other than dispersion correction. Dispersion correction in theoretical determination of cyclopeptide conformations is emphasized. Whether in gas approximation or in solvation simulation, the density functional theory with London dispersion correction (DFT-D3) demonstrates that only 2–3 conformers can stably coexist for cycloaspeptides (A, D, G) at B3LYP-D3 and CAM-B3LYP-D3. Conformational rationality is confirmed by electronic circular dichroism (ECD). Whether for Cotton effect or for excitation energy, TD-B3LYP-D3 has better performances than TD-CAM-B3LYP-D3 because the former can better reproduce the experiment. A molecular orbital analysis is used to interpret ECD, where two energy bands observed in experiment originates from the ππ* transitions other than the σπ* transitions. Long-range correction and solvent effect make H-bonds shorten, and dispersion correction makes them further shorten.