D-term scattering in the resonance Raman spectrum of C60

Gallagher, Sean H.; Armstrong, Robert S.; Lay, Peter A.; Reed, Christopher A.

doi:10.1021/ja00105a075

Cited by 15 publications

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“…C 60 displays 13 classes of RR scattering phenomena, probably more than any other individual molecule, complex, or ion. Recently, we have shown that vibronic coupling 6 and solvent distortion of the sphericity of C 60 1 are integral to the molecule's RR behavior. In a solvent environment, the fast rotation of C 60 is slowed in electrondonating solvents, such as aromatics.…”

Section: Discussionmentioning

confidence: 99%

“…1,6 The H g (7) vibrational mode at 1421 cm -1 receives intensity enhancement through rare D-term scattering, which arises from non-adiabatic vibronic coupling of the LUMO of C 60 with the excited state of the higher energy C (3 1 T 1u -1 1 A g ) transition. 6 Most recently, a RR study of the spectrum of C 60 in a number of solvents revealed that the symmetry of C 60 is sensitive to its solvent environment, giving rise to a proliferation of bands arising from I h IR-active/Raman-silent and I h IR/Raman-silent vibrational modes. 1 Of the I h IR/Ramansilent bands, the one that arises from the G g (4) mode at 1140 cm -1 has an intensity exceeded only by that of the most intense bands of Raman-active modes.…”

Section: Introductionmentioning

confidence: 99%

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Resonance Raman Scattering from Solutions of C₆₀

et al. 1997

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The resonance Raman (RR) spectrum of C60 has been studied in benzene and carbon disulfide using eight excitation wavelengths between 406.7 and 647.1 nm. Raman excitation profile calculations have been performed on the five most intense RR bands; the Hg(1), Ag(1), Gg(4), Hg(7), and Ag(2) vibrational modes. Two main scattering mechanisms predominate, Herzberg−Teller (HT) B-term scattering and nonadiabatic D-term scattering. This is the first observation of rare D-term scattering in a system without a metal. The requirement of a Jahn−Teller distortion of the excited state, produced upon population of the degenerate T1u LUMO, is essentially negated by solvent distortion of the symmetry of C60. While the I h point group is a good descriptor for the 10 fundamental Raman modes of C60, the slight reduction in the high symmetry of the molecule, due to solvent and 13C effects, activates at least 6 of the remaining 36 Raman-silent modes. At resonance with the HOMO−LUMO transition of C60, or its vibronic sideband, the solution resonance Raman spectra of C60 display almost the full gamut of RR scattering phenomena with no fewer than 13 distinct classes of first- and second-order vibrational features. The intensity behavior and the depolarization ratio of the band due to the I h -Raman-silent Gg(4) mode at 1140 cm-1 suggest that the distorted excited state is best approximated as having D 5 d symmetry. The presence of overtones and combinations of Raman-active and Raman-silent vibrational modes is explained in terms of a second-order HT scattering. These studies of the RR spectroscopy of C60 in solution have implications for the electron-pairing mechanism in the superconductivity of fullerides and the nature of solute−solvent associations such as between water-soluble derivatives of C60 and HIV-1 protease.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Resonance Raman Scattering from Solutions of C₆₀

et al. 1997

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“…Symmetry-reduced structures of C 60 would activate some of the otherwise silent I h modes, which could then be amenable to experimental verification as in resonance Raman scattering. [20][21] We performed quantum chemical calculations, at the density functional B3LYP and BPW91 levels, [22][23][24][25][26] and with two different basis sets, on symmetry constrained structures of C 60 : I h , T h , D 5d , D 3d , and S 6 . Results of optimization within these symmetry constraints proved, consistently, that the D 3d structure is the lowest in energy at all levels of theory, being about 35-39 meV even lower than the I h symmetry constrained molecule, as listed in Table I.…”

Section: Enhanced Optical Activity Of Symmetry-reduced C 60mentioning

confidence: 99%

Optimization of Optical and Electronic Properties of Carbon Fullerenes: Symmetry-Reduced C<SUB>60</SUB> and Dumbbell-Like Novel Structures

Manaa¹

2009

Jnl of Comp & Theo Nano

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Using quantum chemical density functional calculations, we study two possible pathways for manipulating the optical and electronic properties of all-carbon fullerenes structures. In the first, the optical properties of C 60 are shown to be enhanced via reduction of the perfectly spherical I h symmetry structure to energetically feasible lower symmetries. A D 3d symmetry structure of C 60 proved to be 39 meV lower in energy than the I h conformation. This reduction in symmetry activates otherwise silent modes in the IR and Raman spectra, possibly achievable via solvation effects. In the second pathway, fusing a building block of an-all carbon hexagonal unit as a connector between two C 60 cages is considered. Optimizations on a resulting series of dumbbell-like structures, molecular C 126 , C 132 , C 138 , C 144 , and C 180 , impart distinct variation in the electronic properties of these novel structures with size of the fused unit. These structures are further shown to support stable anionic radical forms.

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“…2 The model proposed by Suppan neglects several features of the C 60 molecule that we have addressed elsewhere. 2,8,9 The first is that the C 60 molecule is poorly described as a theoretical point quadrupole. It is more akin to an activated surface interacting quite strongly with the surrounding solvent.…”

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Reply to Comment on “Solvent Effects on the Electronic Spectrum of C₆₀”

et al. 1996

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In the preceding comment 1 a number of criticisms were raised concerning our paper 2 on the solvatochromism of C 60 . These criticisms were based, in part, on a recently published theory of the effects of solute quadrupoles on the solvatochromism. 3 The purpose of this comment is to correct some misconceptions in the previous comment and to address the remaining points raised.Suppan 1 has asserted incorrectly that in our paper 1 the quadrupole in the excited state had a moment in "some undefined direction". The proposed axial quadrupole was illustrated clearly in Figure 5 of the original article, 2,4 and the equation defining the quadrupole was given in eq 15; 2 therefore, this assertion is without basis. It was also stated, 1 on the basis of a previous theoretical paper, 3 that a change in quadrupole moment from zero in the ground state to a nonzero value in the excited state cannot result in solvatochromism. Such a postulate is unlikely to be correct, since in the analogous prediction for systems incorporating solvent dipoles, contributions involving products of the polarizability with both µ g ∆µ and (∆µ) 2 are important. 5 This is the basis of our suggestion 2,6 that terms involving ∆Q (i.e., f[Q g ∆Q] and f[(∆Q) 2 ]) are important, which will be addressed in detail elsewhere. 7 Suppan is correct in stating 1 that there cannot be a term involving solvent polarity for C 60 when using a point charge (quadrupole) theory, since this term is a function of Q g ∆Q and, hence, would be zero assuming that C 60 has no ground state quadrupole. His theory 3 also predicts that only the first allowed transition should show significant solvatochromism due to this term. While this has been verified experimentally with molecules, such as benzene, 3 similar behavior is not observed in the solvatochromism of C 60 . 2 The model proposed by Suppan neglects several features of the C 60 molecule that we have addressed elsewhere. 2,8,9 The first is that the C 60 molecule is poorly described as a theoretical point quadrupole. It is more akin to an activated surface interacting quite strongly with the surrounding solvent. These localized effects are likely to invalidate a point charge model with fullerenes, and this is one reason why we have not defined an equation involving ∆Q in the original paper 2 (another criticism in Suppan's comment 1 ). In addition, the solvent/solute interactions involving the C 60 molecule are likely to reduce the symmetry of the molecule in the ground state from the spherical symmetry of the molecule in the gas phase, producing a multipole in the solvated ground state. This solvent-induced distortion of the symmetry is evident in the resonance Raman spectrum of C 60 8,9 and is supported by studies on the rotational reorientation dynamics. 10 These results have been interpreted 10 as having the C 60 molecule spinning on an axis in solution, which implies the formation of an axial quadrupole in the ground state due to specific solvent/solute interactions. Consistent with these results is the observation that ...

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D-term scattering in the resonance Raman spectrum of C60

Cited by 15 publications

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Resonance Raman Scattering from Solutions of C₆₀

Resonance Raman Scattering from Solutions of C₆₀

Optimization of Optical and Electronic Properties of Carbon Fullerenes: Symmetry-Reduced C<SUB>60</SUB> and Dumbbell-Like Novel Structures

Reply to Comment on “Solvent Effects on the Electronic Spectrum of C₆₀”

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D-term scattering in the resonance Raman spectrum of C60

Cited by 15 publications

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Resonance Raman Scattering from Solutions of C60

Resonance Raman Scattering from Solutions of C60

Optimization of Optical and Electronic Properties of Carbon Fullerenes: Symmetry-Reduced C<SUB>60</SUB> and Dumbbell-Like Novel Structures

Reply to Comment on “Solvent Effects on the Electronic Spectrum of C60”

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Resonance Raman Scattering from Solutions of C₆₀

Resonance Raman Scattering from Solutions of C₆₀

Reply to Comment on “Solvent Effects on the Electronic Spectrum of C₆₀”