High‐Accuracy Quantum Chemistry and Chiroptical Properties

Crawford, T. Daniel

doi:10.1002/9781118120187.ch23

Cited by 17 publications

(16 citation statements)

References 142 publications

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“…Indeed, the calculated values predict the correct sign of all compounds, except that of (S p ,S)-5. The calculated absolute values are also very good, with two exceptions; it should be remembered that, by rule of thumb, computed DFT results may be considered reliable only up to 50 [α] D absolute values, [39,40] above which more complete approaches should be 7361 considered. The reasons for some discordant results may be ascribed to two factors influencing the performance of calculations, such as the population of the conformers and the representation of electronic functions (e.g., correlations as in CI).…”

Section: Or Valuesmentioning

confidence: 94%

Chiroptical Signatures of Planar and Central Chirality in [2]Paracyclo[2](5,8)quinolinophane Derivatives

et al. 2014

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Electronic and vibrational circular dichroism (ECD and VCD) spectra and specific optical rotation measurements at the sodium D-line (OR) have been taken for thirteen chiral [2]-paracyclo[2](5,8)quinolinophane derivatives and calculated by density functional theory. Besides the planar chirality from the paracyclophane moiety in all molecules, some of the investigated compounds also exhibit central chirality due to an\ud asymmetric carbon atom in the side-chain bound at C-2 of the heterocyclic ring. Characteristic bands for each type ofchirality were clearly identified in the VCD spectra in the CH-stretching and mid-IR regions, allowing assignment of absolute and relative configurations. ECD was found to be sensitive mostly, if not exclusively, to planar chirality, whereas OR was also very sensitive to central chirality. Configurational assignment of the different diastereomers by the\ud present method provided results that are in agreement with those inferred from NOE-NMR experiments

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Section: Or Valuesmentioning

confidence: 94%

Chiroptical Signatures of Planar and Central Chirality in [2]Paracyclo[2](5,8)quinolinophane Derivatives

et al. 2014

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“…Figure 2 clearly shows a large variability of the OR as a function of the particular geometrical arrangement of water around the target molecule. The OR can vary sensitively, not only in absolute value, but especially in sign, taking any value in the range 2150/150 deg dm 21 g 21 cm 3 . This means that any static approach to such property, such as the PCM or simple cluster-based models, where the specific interaction is modeled by redefining the solute as the target molecule plus a limited number of explicitly treated solvent molecules, will most probably give a result falling in this range, however, a good reproduction of the average value is not guaranteed.…”

Section: The or Of (R)-methyloxiranementioning

confidence: 99%

“…K E Y W O R D S aqueous solutions, chirality, polarizable embedding, solvent effects, quantum mechanical/molecular mechanics 1 | I N T R O D U C T I O N The calculation of chiroptical properties and chiral spectra by means of Quantum-Mechanical (QM) methods [1-5] is a mature research field. Many theoretical developments have been reported in the literature, focusing on the different aspects (accuracy in the description of the molecular Hamiltonian, choice of the basis set, inclusion of environmental effects) [3,[6][7][8][9] which may contribute to reach an accurate description of chirality. The definition of accurate protocols is nowadays accompanied by several applications, which demonstrate that a significant level of accuracy is accessible, so that QM calculations are universally accepted as a powerful methodology to assist the determination of the molecular absolute configuration.…”

mentioning

confidence: 99%

Integrated QM/polarizable MM/continuum approaches to model chiroptical properties of strongly interacting solute–solvent systems

Cappelli

2016

Int J of Quantum Chemistry

140

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Solvent effects on chiroptical properties and spectroscopies can be huge, and affect not only the absolute value but the sign of molecular chiroptical responses. Therefore, the definition of reliable theoretical models and computational protocols to calculate chiroptical responses and assist the assignment of the chiral absolute configuration cannot overlook the effects of the surrounding environment. Continuum solvation methodologies are successful in case of weakly interacting solute-solvent couples, whereas in case of strongly interacting systems, such as those dominated by explicit hydrogen bonding interaction, a change of strategy is required to gain a reliable modeling.In this review, a recently developed integrated Quantum-Mechanical/Polarizable molecular mechanics (MM)/polarizable continuum model (PCM) method is discussed, which combines a fluctuating charge approach to the MM polarization with the PCM. Its theoretical fundamentals, and issues related to the calculation of chiroptical responses are summarized, and the application to few representative test cases in aqueous solution is discussed.aqueous solutions, chirality, polarizable embedding, solvent effects, quantum mechanical/molecular mechanics | I N T R O D U C T I O NThe calculation of chiroptical properties and chiral spectra by means of Quantum-Mechanical (QM) methods [1][2][3][4][5] is a mature research field.Many theoretical developments have been reported in the literature, focusing on the different aspects (accuracy in the description of the molecular Hamiltonian, choice of the basis set, inclusion of environmental effects) [3,[6][7][8][9] which may contribute to reach an accurate description of chirality. The definition of accurate protocols is nowadays accompanied by several applications, which demonstrate that a significant level of accuracy is accessible, so that QM calculations are universally accepted as a powerful methodology to assist the determination of the molecular absolute configuration.[10]In case of standard (non-chiral) spectroscopies, the most relevant information which is extracted from spectra is mainly related to peak positions (energies), whereas peak intensities play a secondary role. This is reflected in the computational methodologies which have been developed so far, which are mainly interested in getting an accurate reproduction of peak positions (infrared/Raman wavenumbers, UV-Vis transition energies, NMR chemical shieldings, etc.), reserving instead much less attention to spectral intensities. [11][12][13] In case of chiroptical properties/spectroscopies, an opposite situation occurs, in fact not only the absolute value but also especially the sign of the spectroscopic response is the most relevant information taken from the spectra. This feature makes chiroptical properties among the most challenging for theoretical models, and the difficulties in their accurate modeling are further increased by that fact that they are formally mixed electricmagnetic properties, where the effects of both the fields are ...

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“…[1][2][3][4][5][6] The latter techniques have gained increasing interest recently as valuable tools for assigning the absolute configurations and for obtaining information on the local environment of oscillating modes of molecular systems and on conformational ratios important in determining reactivities of biomolecules. 5,7 The tremendous progress of ab initio quantum chemistry in such a field has been reflected in the larger number of applications of QM approaches to the calculation of chiroptical properties and spectroscopies.…”

Section: Introductionmentioning

confidence: 99%

Origin invariance in vibrational resonance Raman optical activity

Vidal

Egidi

Barone

et al. 2015

The Journal of Chemical Physics

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A theoretical investigation on the origin dependence of the vibronic polarizabilities, isotropic and anisotropic rotational invariants, and scattering cross sections in Resonance Raman Optical Activity (RROA) spectroscopy is presented. Expressions showing the origin dependence of these polarizabilities were written in the resonance regime using the Franck-Condon (FC) and Herzberg-Teller (HT) approximations for the electronic transition moments. Differently from the far-from-resonance scattering regime, where the origin dependent terms cancel out when the rotational invariants are calculated, RROA spectrum can exhibit some origin dependence even for eigenfunctions of the electronic Hamiltonian. At the FC level, the RROA spectrum is completely origin invariant if the polarizabilities are calculated using a single excited state or for a set of degenerate states. Otherwise, some origin effects can be observed in the spectrum. At the HT level, RROA spectrum is origin dependent even when the polarizabilities are evaluated from a single excited state but the origin effect is expected to be small in this case. Numerical calculations performed for (S)-methyloxirane, (2R,3R)-dimethyloxirane, and (R)-4-F-2-azetidinone at both FC and HT levels using the velocity representation of the electric dipole and quadrupole transition moments confirm the predictions of the theory and show the extent of origin effects and the effectiveness of suggested ways to remove them.

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High‐Accuracy Quantum Chemistry and Chiroptical Properties

Cited by 17 publications

References 142 publications

Chiroptical Signatures of Planar and Central Chirality in [2]Paracyclo[2](5,8)quinolinophane Derivatives

Chiroptical Signatures of Planar and Central Chirality in [2]Paracyclo[2](5,8)quinolinophane Derivatives

Integrated QM/polarizable MM/continuum approaches to model chiroptical properties of strongly interacting solute–solvent systems

Origin invariance in vibrational resonance Raman optical activity

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