Light-Induced Pyramidal Inversion of Sulfoxides<sup>1</sup>

Mislow, Kurt; Axelrod, Michael; Rayner, Dennis R.; Gotthardt, Hans; Coyne, Lelia M.; Hammond, George S.

doi:10.1021/ja00949a052

Cited by 69 publications

(36 citation statements)

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“…Without entering into details of bar formation, SB galaxies can be seen as an intermediate state between chirallydefined systems (S-galaxies) and system which are loosing, by gravitational interactions, their chiral features (E and S0 galaxies) since they are living in much dense environments. Gravitational field and tidal encounters act as a sort of thermic or photo-induced racemization for enantiopure compounds (Rayner et al, 1968;Mislow et al, 1965). In other words, starting from a well-defined chiral modality (trailing S-galaxies), an evolution through a pseudo-racemic mixture (S and SBgalaxies) and toward completely achiral objects (E, S0 galaxies) can be envisaged.…”

Section: Discussionmentioning

confidence: 99%

Spiral Galaxies as Chiral Objects?

Capozziello

Lattanzi

2006

Astrophys Space Sci

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Abstract. Spiral galaxies show axial symmetry and an intrinsic 2D-chirality. Environmental effects can influence the chirality of originally isolated stellar systems and a progressive loss of chirality can be recognised in the Hubble sequence. We point out a preferential modality for genetic galaxies as in microscopic systems like aminoacids, sugars or neutrinos. This feature could be the remnant of a primordial symmetry breaking characterizing systems at all scales.

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Section: Discussionmentioning

confidence: 99%

Spiral Galaxies as Chiral Objects?

Capozziello

Lattanzi

2006

Astrophys Space Sci

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“…2 Thus, the reactivity of sulfoxides in polar, radical, and photochemical processes has been the object of much investigation. 3 In contrast, the behavior of sulfoxides in electron transfer oxidation reactions has been little studied, probably due to the relatively high oxidation potential of these species. 4 Consequently, little is known about sulfoxide radical cations, the few studies presently available exclusively concerning dialkyl sulfoxide radical cations.…”

Section: Introductionmentioning

confidence: 99%

Aryl Sulfoxide Radical Cations. Generation, Spectral Properties, and Theoretical Calculations

et al. 2006

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Aromatic sulfoxide radical cations have been generated by pulse radiolysis and laser flash photolysis techniques. In water (pulse radiolysis) the radical cations showed an intense absorption band in the UV region (ca. 300 nm) and a broad less intense band in the visible region (from 500 to 1000 nm) whose position depends on the nature of the ring substituent. At very low pulse energy, the radical cations decayed by first-order kinetics, the decay rate increasing as the pH increases. It is suggested that the decay involves a nucleophilic attack of H(2)O or OH(-) (in basic solutions) to the positively charged sulfur atom to give the radical ArSO(OH)CH(3)(*). By sensitized [N-methylquinolinium tetrafluoborate (NMQ(+))] laser flash photolysis (LFP) the aromatic sulfoxide radical cations were generated in acetonitrile. In these experiments, however, only the band of the radical cation in the visible region could be observed, the UV band being covered by the UV absorption of NMQ(+). The lambda(max) values of the bands in the visible region resulted almost identical to those observed in water for the same radical cations. In the LFP experiments the sulfoxide radical cations decayed by second-order kinetics at a diffusion-controlled rate, and the decay is attributed to the back electron transfer between the radical cation and NMQ(*). DFT calculations were also carried out for a number of 4-X ring substituted (X = H, Me, Br, OMe, CN) aromatic sulfoxide radical cations (and their neutral parents). In all radical cations, the conformation with the S-O bond almost coplanar with the aromatic ring is the only one corresponding to the energy minimum. The maximum of energy corresponds to the conformation where the S-O bond is perpendicular to the aromatic ring. The rotational energy barriers are not very high, ranging from 3.9 to 6.9 kcal/mol. In all radical cations, the major fraction of charge and spin density is localized on the SOMe group. However, a substantial delocalization of charge and spin on the ring (almost 50% for the 4-methoxy derivative and around 30% for the other radical cations) is also observed. This suggests some conjugative interaction between the MeSO group and the aromatic system that may become very significant when a strong electron donating substituent like the MeO group is present. The ionization energies (IE) of the 4-X ring substituted neutral aromatic sulfoxides were also calculated, which were found to satisfactorily correlate with the experimental E(p) potentials measured by cyclic voltammetry.

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“…21 Stereomutation of sulfoxides can also be induced photochemically. 22 Restricting the discussion to directly irradiated cases, two limiting mechanisms have generally been advanced. The first derives from the well-known R-cleavage photochemistry of sulfoxides that produces an alkyl radical and a sulfinyl radical.…”

Section: Introductionmentioning

confidence: 99%

Computational Studies of the Ground and Excited State Potentials of DMSO and H₂SO: Relevance to Photostereomutation

Cubbage

Jenks

2001

J. Phys. Chem. A

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A computational study on ground and excited states of dimethyl sulfoxide (DMSO) and the hypothetical molecule H 2 SO is reported. Full valence CASSCF/6-311+G(3df,2p) with a multireference perturbation theory correction was used for the latter, while DMSO was examined with an active space that neglected only the CH bonds and an analogous basis set that neglected polarization functions on H. A realistic value of 41.5 kcal/mol was obtained for the ground state pyramidal inversion of sulfur for DMSO, though no directly comparable experimental value is available. Calculations were also carried out on singlet and triplet excited state surfaces of both A′ and A′′ symmetry. Relaxed excited state geometries fairly near the ground state geometry were found, but perhaps more importantly, excited state stationary points were also found in C 2V symmetry. These were the lowest energy of any geometry on their respective surfaces. This leads to the speculation that photochemical stereomutation of alkyl sulfoxides may occur without C-S bond cleavage in a mechanism formally analogous to the photochemical cis-trans isomerization of olefins.

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Light-Induced Pyramidal Inversion of Sulfoxides¹

Cited by 69 publications

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Spiral Galaxies as Chiral Objects?

Spiral Galaxies as Chiral Objects?

Aryl Sulfoxide Radical Cations. Generation, Spectral Properties, and Theoretical Calculations

Computational Studies of the Ground and Excited State Potentials of DMSO and H₂SO: Relevance to Photostereomutation

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Light-Induced Pyramidal Inversion of Sulfoxides1

Cited by 69 publications

References 0 publications

Spiral Galaxies as Chiral Objects?

Spiral Galaxies as Chiral Objects?

Aryl Sulfoxide Radical Cations. Generation, Spectral Properties, and Theoretical Calculations

Computational Studies of the Ground and Excited State Potentials of DMSO and H2SO: Relevance to Photostereomutation

Contact Info

Product

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Light-Induced Pyramidal Inversion of Sulfoxides¹

Computational Studies of the Ground and Excited State Potentials of DMSO and H₂SO: Relevance to Photostereomutation