A Vibrational Raman Optical Activity Study of 1,1′‐Binaphthyl Derivatives

Abstract

The Raman polarized and vibrational Raman optical activity (VROA) backward spectra are simulated for a series of 2,2'-substituted 1,1'-binaphthyl compounds presenting a variety of torsion angles between the two naphthalene rings. The substitution prevents free rotation along this torsion angle and the chirality of these compounds is thus called atropisomerism. However, the rotation is not completely frozen so that two different conformations, namely cisoid and transoid, are found and their Raman and VROA signatures are studied. As expected, the Raman spectra are not very sensitive whereas the VROA spectra present more complex patterns, which evolve as a function of the torsion angle between the two naphthalene groups. In particular, our analysis shows that some modes can be used as a probe for the determination of the torsion angle of these molecules in solution. The contributions of both invariants to the VROA backward intensity are also assessed.

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

“…(It should be noted here that although the γ dihedral angle is not associated with the largeamplitude motion of the solvent molecules, variations in γ induce variations in the α angle that are related to the large-amplitude motion of the solvent. We also note that Bour et al 36 and Liegeois et al 37 have carried out investigations similar to our γ LT calculations here for systems very similar to the one considered here.) Finally, we note that, because the C 3 −(DMSO) 2 complex has C 2 symmetry (like the isolated C 3 conformer), there are two α, two β, and two δ LT parameters (one for each solvent molecule).…”

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

“…To simulate the effects induced in the spectra by the large amplitude pseudorotations performed by the two methoxy groups, the relative orientation of the two carbonyl groups was systematically varied by performing linear transit (LT) calculations (described in section ) for the C 2 -(CDCl 3 ) 2 and C 3 -(CDCl 3 ) 2 molecular complexes. This approach had been tried somewhat empirically previously, − but here we proposed, as also proposed in ref 56, to Boltzmann average the VA and VCD spectra of all LT structures, as for hindered rotations or torsions defining flat energy curves, it is practically impossible to define an absolute energy minimum. Two dihedral angles have been varied during the LT calculations, i.e., O 3 C 13 C 12 C 11 and O 2 C 14 C 11 C 12 (the atoms defining these two angles are shown in Figure ; see also the IUPAC numbering in Scheme ).…”

In Situ Ultralow-Frequency Raman Tracking of the Polymorphic Transformation of Crystalline 1,1′-Binaphthyl

“…BN is a typical biaryl compound that has been the subject of extensive studies in the condensed phase − as well as in the gas phase . It occurs as two distinct crystal forms.…”