3 research outputs found
Understanding Solvent Effects in Vibrational Circular Dichroism Spectra: [1,1′-Binaphthalene]-2,2′-diol in Dichloromethane, Acetonitrile, and Dimethyl Sulfoxide Solvents
We present a combined experimental and computational
investigation
of the vibrational absorption (VA) and vibrational circular dichroism
(VCD) spectra of [1,1′-binaphthalene]-2,2′-diol. First,
the sensitive dependence of the experimental VA and VCD spectra on
the solvent is demonstrated by comparing the experimental spectra
measured in CH<sub>2</sub>Cl<sub>2</sub>, CD<sub>3</sub>CN, and DMSO-<i>d</i><sub>6</sub> solvents. Then, by comparing calculations
performed for the isolated solute molecule to calculations performed
for molecular complexes formed between solute and solvent molecules,
we identify three main types of perturbations that affect the shape
of the VA and VCD spectra when going from one solvent to another.
These sources of perturbations are (1) perturbation of the Boltzmann
populations, (2) perturbation of the electronic structure, and (3)
perturbation of the normal modes
The Importance of Large-Amplitude Motions for the Interpretation of Mid-Infrared Vibrational Absorption and Circular Dichroism Spectra: 6,6′-Dibromo-[1,1′-binaphthalene]-2,2′-diol in Dimethyl Sulfoxide
Using the 6,6′-dibromo-[1,1′-binaphthalene]-2,2′-diol
molecule and its vibrational absorption (VA) and vibrational circular
dichroism (VCD) spectra measured in deuterated dimethyl sulfoxide
as example, we present a first detailed study of the effects induced
in VCD spectra by the large-amplitude motions of solvent molecules
loosely bound to a solute molecule. We show that this type of perturbation
can induce significant effects in the VA and VCD spectra. We also
outline a computational procedure that can effectively model the effects
induced in the spectra and at the same time provide detailed structural
information regarding the relative orientations of moieties involved
in a solute–solvent molecular complex
Importance of C*–H Based Modes and Large Amplitude Motion Effects in Vibrational Circular Dichroism Spectra: The Case of the Chiral Adduct of Dimethyl Fumarate and Anthracene
The role played by the C*–H
based modes (C* being the chiral
carbon atom) and the large amplitude motions in the vibrational absorption
(VA) and vibrational circular dichroism (VCD) spectra is investigated.
The example of an adduct of dimethyl fumarate and anthracene, i.e.,
dimethyl-(+)-(11<i>R</i>,12<i>R</i>)-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylate,
and two deuterated isotopomers thereof specially synthesized for this
goal, are considered. By comparing the experimental and DFT calculated
spectra of the undeuterated and deuterated species, we demonstrate
that the C*–H bending, rocking, and stretching modes in the
VA and VCD spectra are clearly identified in well defined spectroscopic
features. Further, significant information about the conformer distribution
is gathered by analyzing the VA and VCD data of both the fingerprint
and the C–H stretching regions, with particular attention paid
to the band shape data. Effects related to the large amplitude motions
of the two methoxy moieties have been simulated by performing linear
transit (LT) calculations, which consists of varying systematically
the relative positions of the two methoxy moieties and calculating
VCD spectra for the partially optimized structures obtained in this
way. The LT method allows one to improve the quality of calculated
spectra, as compared to experimental results, especially in regard
to relative intensities and bandwidths