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Volumn 692, Issue 13, 2007, Pages 2705-2715

Computational modeling of isotropic electron paramagnetic resonance spectra of doublet state main group radicals

Author keywords

DFT calculations; EPR spectroscopy; Main group radicals; Spectral simulation

Indexed keywords

COMPLEXATION; COMPUTATIONAL METHODS; COMPUTER SIMULATION; DENSITY FUNCTIONAL THEORY; PARAMAGNETIC RESONANCE;

EID: 34248209083     PISSN: 0022328X     EISSN: None     Source Type: Journal    
DOI: 10.1016/j.jorganchem.2006.12.019     Document Type: Article
Times cited : (12)

References (82)
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    • For radicals in which the spin density is highly delocalized over several hydrogen and nitrogen nuclei, the EPR spectra can, however, become increasingly complex. See, for example, the EPR spectrum reported for the cation radical of 6-hydrodipyrido[1,2-c:2′,1′-e]-imidazole in
    • For radicals in which the spin density is highly delocalized over several hydrogen and nitrogen nuclei, the EPR spectra can, however, become increasingly complex. See, for example, the EPR spectrum reported for the cation radical of 6-hydrodipyrido[1,2-c:2′,1′-e]-imidazole in. Sullivan P.D., Fong J.Y., and Williams M.L. J. Phys. Chem. 82 (1978) 1181
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    • See, for example, discussion in Ref. [1].
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    • For a more in-depth discussion of the theory behind EPR spectroscopy, see Ref. [1].
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    • For this reason, Slater-type orbitals (STO) should, in principle, show superior performance in calculation of hfc constants. Comparison of results at various DFT levels of theory has, however, shown that in practice both STO- and GTO-based approaches yield results of comparable accuracy. See Chapter 29 in Ref. [7].
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    • For recent benchmarks, see. Chong D.P. (Ed), World Scientific, Singapore (Chapter 8)
    • For recent benchmarks, see. Barone V. In: Chong D.P. (Ed). Recent Advances in Density Functional Methods vol. 1 (1996), World Scientific, Singapore (Chapter 8)
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    • For a recent review on main group radicals, see. Power P.P. Chem. Rev. 103 (2003) 789
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    • See discussion in Chapters 5 and 29 of Ref. [7].
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    • See discussion in Chapter 30 of Ref. [7].
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    • See discussion in Chapter 29 of Ref. [7].
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    • See discussion in Chapters 29 and 35 of Ref. [7].
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    • An important exception to this rule is observed with transition metal compounds for which none of the current density functionals shows uniform performance.
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    • The analysis of EPR spectra using iterative least-squares fit methods has been reviewed in
    • The analysis of EPR spectra using iterative least-squares fit methods has been reviewed in. Kriste B. Anal. Chim. Acta 265 (1992) 191
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    • For radicals containing nuclei that have more than one naturally abundant spin-active isotope, the simulation is done by using a weighted sum of individual subspectra for each isotopomer. The weight factors can be readily calculated from the relative abundances of the different isotopes.
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    • note
    • In this paper we have omitted lineshape related questions from the discussion mainly for simplicity. In addition, all EPR spectra presented in Section 3 can be simulated using either pure or almost pure (i.e. small Gaussian component) Lorenzian lineshape. However, we wish to point out here that in many cases the experimental EPR spectra can show linewidth variations due to internal dynamics (alternating lineshape) or slow molecular tumbling (asymmetric lineshape). In such cases, accurate simulations of the EPR spectra require the use of approaches which are capable of dealing with more complex lineshape functions.
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    • note
    • We note here that application of various peak difference search methods yields only ambiguous estimates of hfcs, because a multitude of sums and differences are generally found from the experimental spectrum in addition to the relevant parameters. In addition, whereas ENDOR spectroscopy can effectively provide high-quality values for hfcs, the number of each equivalent nucleus is not by any means clear from the measured spectra. Hence, this information must be determined separately either by using chemical considerations or time consuming "brute force" approaches in which several different EPR simulations with varying number of nuclei are performed.
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    • tBu groups are replaced with Me groups were used to speed up the calculations. In the present case, such alteration is expected to have a negligible effect on the electronic structures and the spin density distributions of the radical species 2a-d.
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    • note
    • We note that the indium species 2d is a transient radical and even though its characterization was carried out at -40 °C, the recorded EPR spectrum still shows some signals belonging to the decomposition products.
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    • Another possibility is that the hfcs are almost equal by chance. In such a case one would, however, expect that the spectral lines would be much broader (cf. EPR spectra in Fig. 2).
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    • note
    • To accurately model the experimental spectra, a third-order perturbation theory based Hamiltonian was utilized when creating the spectral simulations.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.