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Testing the vibrational exciton and the local mode models on the instructive cases of dicarvone, dipinocarvone, and dimenthol vibrational circular dichroism spectra
Author(s) -
Mazzeo Giuseppe,
Santoro Ernesto,
Abbate Sergio,
Zonta Cristiano,
Fabris Fabrizio,
Longhi Giovanna
Publication year - 2020
Publication title -
chirality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.43
H-Index - 77
eISSN - 1520-636X
pISSN - 0899-0042
DOI - 10.1002/chir.23232
Subject(s) - vibrational circular dichroism , chemistry , overtone , exciton , density functional theory , molecular vibration , infrared spectroscopy , spectral line , molecular physics , infrared , hot band , crystallography , circular dichroism , computational chemistry , molecule , optics , physics , organic chemistry , condensed matter physics , astronomy
The vibrational circular dichroism (VCD) spectra of dicarvone ( 1 ), dipinocarvone ( 2 ), and dimenthol ( 3 ) have been recorded in the range 900–3200 cm −1 , encompassing the mid‐infrared (mid‐IR), the CO stretching, and the CH‐stretching regions. For compound 3 also, the fundamental and the first overtone OH stretching regions have been investigated by IR/NIR absorption and VCD. Density functional theory (DFT) calculations allow one to interpret the IR and VCD spectra and to confirm the configuration/conformational studies previously conducted by X‐ray diffraction. The most intense VCD signals are associated with the vibrational normal modes involving symmetry‐related groups close to the CC bond connecting covalently the two molecular units. The vibrational exciton (VCDEC) model is fruitfully tested on the VCD data of compounds 1 and 2 for the spectroscopic regions at ~1700 cm −1 , and the local mode model is tested on compound 3 at ~3500 and ~6500 cm −1 . For compounds 1 and 2 also, ECD spectra are reported, and the exciton mechanism is tested also there, and connections to the VCDEC model are examined.