Communication: Fullerene resolution by the magnetic circular dichroism

Štěpánek, Petr; Straka, Michal; Andrushchenko, Valery; Bouř, Petr

doi:10.1063/1.4802763

Cited by 20 publications

(9 citation statements)

References 44 publications

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“…Magnetic circular dichroism (MCD) is a technique not as common as ECD; yet its applicability has been recently enhanced by the possibility to reliably simulate spectra from the first principles using publicly available software only . Typically, molecules with conjugated π‐electrons, such as porphyrins, are studied by MCD, as these provide a strong signal, whereas their ECD would be zero or small due to molecular symmetry …”

Section: Introductionmentioning

confidence: 99%

Origin‐independent sum over states simulations of magnetic and electronic circular dichroism spectra via the localized orbital/local origin method

Štěpánek

Bouř

2015

J Comput Chem

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Although electronic and magnetic circular dichroism (ECD, MCD) spectra reveal valuable details about molecular geometry and electronic structure, quantum-chemical simulations significantly facilitate their interpretation. However, the simulated results may depend on the choice of coordinate origin. Previously (Štěpánek and Bouř, J. Comput. Chem. 2013, 34, 1531), the sum-over-states (SOS) methodology was found useful for efficient MCD computations. Approximate wave functions were "resolved" using time-dependent density functional theory, and the origin-dependence was avoided by placing the origin to the center of mass of the investigated molecule. In this study, a more elegant way is proposed, based on the localized orbital/local origin (LORG) formalism, and a similar approach is also applied to generate ECD intensities. The LORG-like approach yields fully origin-independent ECD and MCD spectra. The results thus indicate that the computationally relatively cheap SOS simulations open a new way of modeling molecular properties, including those involving the origin-dependent magnetic dipole moment operator.

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Section: Introductionmentioning

confidence: 99%

Origin‐independent sum over states simulations of magnetic and electronic circular dichroism spectra via the localized orbital/local origin method

Štěpánek

Bouř

2015

J Comput Chem

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“…34,35 Interest in MCD spectra of fullerenes is vivid till our days. 36,37 a) Email: szabados@chem.elte.hu Though no CCNS measurements have been reported yet, vibrational optical activity 38,39 (VOA) is especially appealing for structural studies on chiral systems. 40 On one hand, VOA is a promising method-complementary to ECD 41,42 -when aiming enantiomer identification.…”

Section: Introductionmentioning

confidence: 99%

Vibrational optical activity of chiral carbon nanoclusters treated by a generalized π-electron method

Nagy

Śurján

Szabados

2014

The Journal of Chemical Physics

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Cross sections of inelastic light scattering accompanied by vibronic excitation in large conjugated carbon structures is assessed at the π-electron level. Intensities of Raman and vibrational Raman optical activity (VROA) spectra of fullerenes are computed, relying on a single electron per atom. When considering only first neighbor terms in the Hamiltonian (a tight-binding (TB) type or Hückel-model), Raman intensities are captured remarkably well, based on comparison with frequency-dependent linear response of the self-consistent field (SCF) method. Resorting to π-electron levels when computing spectral intensities brings a beneficial reduction in computational cost as compared to linear response SCF. At difference with total intensities, the first neighbor TB model is found inadequate for giving the left and right circularly polarized components of the scattered light, especially when the molecular surface is highly curved. To step beyond first neighbor approximation, an effective π-electron Hamiltonian, including interaction of all sites is derived from the all-electron Fockian, in the spirit of the Bloch-equation. Chiroptical cross-sections computed by this novel π-electron method improve upon first-neighbor TB considerably, with no increase in computational cost. Computed VROA spectra of chiral fullerenes, such as C76 and C28, are reported for the first time, both by conventional linear response SCF and effective π-electron models.

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“…In the past, the CPP method has been used to investigate a variety of molecular properties such as natural optical activity, 39 x-ray absorption, 40 dispersion forces, 41 two-photon absorption, 42 and MCD. 27,37,38 MCD calculations using related damped response theory approaches have also been performed by Krykunov et al 43 and by Kjaergaard et al 34 Ref. 44 reported recently a real-time density-functional theory (DFT) method for calculating both the A and B terms.…”

Section: Introductionmentioning

confidence: 99%

“…generalized to nuclear spin-induced circular dichroism (NSCD), where the nuclear magnetization causes a differential absorption of left-and right-circularly polarized light, expressible via induced elliptic polarization onto the incident linearly polarized light. 1 Whereas the MCD ellipticity provides information on the excitations occurring in the entire molecule, and may be used for analytic purposes such as, e.g., to distinguish different fullerenes as shown in recent work, 27 NSCD furnishes a nuclear site-specific observable that may, at least in principle, be used to obtain a high-resolution spectrum. The ubiquitous Faraday B term contribution to MCD, arising from magnetic mixing of the excited states, 2 has in the past been obtained in electronic structure calculations by the analytical residues of appropriate quadratic response functions 28 (QRFs) or magnetic-field derivatives of transition strengths, 29,30 sometimes combined with empirical lineshape functions to simulate the spectral profiles.…”

Section: Introductionmentioning

confidence: 99%

Nuclear spin circular dichroism

Vaara¹,

Rizzo²,

Kauczor³

et al. 2014

The Journal of Chemical Physics

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Articles you may be interested inMagnetic circular dichroism of symmetry and spin forbidden transitions of high-spin metal ions J. Chem. Phys. 113, 5003 (2000) Recent years have witnessed a growing interest in magneto-optic spectroscopy techniques that use nuclear magnetization as the source of the magnetic field. Here we present a formulation of magnetic circular dichroism (CD) due to magnetically polarized nuclei, nuclear spin-induced CD (NSCD), in molecules. The NSCD ellipticity and nuclear spin-induced optical rotation (NSOR) angle correspond to the real and imaginary parts, respectively, of (complex) quadratic response functions involving the dynamic second-order interaction of the electron system with the linearly polarized light beam, as well as the static magnetic hyperfine interaction. Using the complex polarization propagator framework, NSCD and NSOR signals are obtained at frequencies in the vicinity of optical excitations. Hartree-Fock and density-functional theory calculations on relatively small model systems, ethene, benzene, and 1,4-benzoquinone, demonstrate the feasibility of the method for obtaining relatively strong nuclear spin-induced ellipticity and optical rotation signals. Comparison of the proton and carbon-13 signals of ethanol reveals that these resonant phenomena facilitate chemical resolution between non-equivalent nuclei in magneto-optic spectra. © 2014 AIP Publishing LLC.

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Communication: Fullerene resolution by the magnetic circular dichroism

Cited by 20 publications

References 44 publications

Origin‐independent sum over states simulations of magnetic and electronic circular dichroism spectra via the localized orbital/local origin method

Origin‐independent sum over states simulations of magnetic and electronic circular dichroism spectra via the localized orbital/local origin method

Vibrational optical activity of chiral carbon nanoclusters treated by a generalized π-electron method

Nuclear spin circular dichroism

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