<i>Ab initio</i> calculation of magnetic circular dichroism

Magnetic circular dichroism (MCD) spectroscopy has been established as a convenient method to study electronic structure, in particular for small symmetric organic molecules. Newer applications on more complex systems are additionally stimulated by the latest availability of precise quantum-chemical techniques for the spectral simulations. In this work, a sum over states (SOS) summation is reexamined as an alternative to the derivative techniques for the MCD modeling. Unlike in previous works, the excited electronic states are calculated by the time-dependent density functional theory (TDDFT). A gradient formulation of the MCD intensities is also proposed, less dependent on the origin choice than the standard expressions. The dependencies of the results on the basis set, number of electronic states, and coordinate origin are tested on model examples, including large symmetric molecules with degenerate electronic states. The results suggest that the SOS/TDDFT approach is a viable and accurate technique for spectral simulation. It may even considerably reduce the computational time, if compared with the traditional MCD computational procedures based on the response theory.

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“…For comparison, the SOS MCD intensities were compared to those obtained by the RT method as implemented in the Dalton program, version “2011.”…”

Section: Methodsmentioning

confidence: 99%

Computation of magnetic circular dichroism by sum‐over‐states summations

Štěpánek

Bouř

2013

J Comput Chem

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“…4 After a few relatively scarce studies at Hartree-Fock, MCSCF 4 and Coupled Cluster 5,6 levels of theory, a boost in the applications has come from the extension of the computational methodology within the realm of Time-Dependent Density Functional Theory (TD-DFT), resulting in the ability to address larger systems. [7][8][9][10][11][12][13][14][15][16][17][18][19] Beside the residue-based approach of Refs. 4,6,11,16, so-called complex polarization propagator (also known as damped response theory) methods 12,13,20 -as well as realtime methods 21 -have emerged in the last decade along with modern versions of sum-over-states approaches; 22,23 relativistic schemes have also been proposed.…”

Section: Introductionmentioning

confidence: 99%

“…47 As thoroughly reviewed in Ref. 18 In the framework of response theory, MCD spectra can be computed in two ways. In the first one, the sum-over-state expressions of the A, B and C terms derived by Buckingham and…”

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confidence: 99%

TD-DFT Investigation of the Magnetic Circular Dichroism Spectra of Some Purine and Pyrimidine Bases of Nucleic Acids

et al. 2015

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We present a computational study of the magnetic circular dichroism (MCD) spectra in the 200-300 nm wavelength region of purine and its derivative hypoxanthine, as well as of the pyrimidine bases of nucleic acids uracil, thymine, and cytosine, using the B3LYP and CAM-B3LYP functionals. Solvent effects are investigated within the polarizable continuum model and by inclusion of explicit water molecules. In general, the computed spectra are found to be in good agreement with the experimental ones, apart from some overall blue shifts. Both the pseudo-A term shape of the MCD spectra of the purines and the B term shape of the spectra of pyrimidine bases are reproduced. Our calculations also correctly reproduce the reversed phase of the MCD bands in purine compared to that of its derivatives present in nucleic acids. Solvent effects are sizable and system specific, but they do not in general alter the qualitative shape of the spectra. The bands are dominated by the bright π → π* transitions, and our calculations in solution nicely reproduce their energy differences, improving the estimates obtained in the gas phase. Shoulders are predicted for purine and uracil due to n → π* excitations, but they are too weak to be observed in the experiment.

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“…Theoretical analysis of these effects involves nonlinear interactions between the electromagnetic beam, B 0 , and the electronic wave function of the system in question. 1,[6][7][8] As shown in 2006 by Savukov, Lee, and Romalis, 9 magneto-optic effects can also be caused by the field due to the collective magnetization of nuclei, such as typically used in nuclear magnetic resonance experiments. In Ref.…”

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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Ab initio calculation of magnetic circular dichroism

Cited by 35 publications

References 81 publications

Computation of magnetic circular dichroism by sum‐over‐states summations

Computation of magnetic circular dichroism by sum‐over‐states summations

TD-DFT Investigation of the Magnetic Circular Dichroism Spectra of Some Purine and Pyrimidine Bases of Nucleic Acids

Nuclear spin circular dichroism

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