A single-crystal structure determination of DL-6-thioctic acid, C8H14O2S2

Stroud, R. M.; Carlisle, C. H.

doi:10.1107/s0567740872002225

Cited by 37 publications

(17 citation statements)

References 2 publications

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“…1,2-Dithiolane in the Gas Phase. The geometry of 1,2-dithiolane with the intact disulfide bond (cyclic 1,2-dithiolane) was taken from the crystal structure of DL-6-thioctic acid 69 and optimized in the gas phase using B3LYP. The final structure had a SsS distance of 2.120 Å and a CSSC dihedral angle of 33.0°, in agreement with the crystal structurevalues (2.053 Å and 34.5°).…”

Section: Resultsmentioning

confidence: 99%

Electron Transport through Cyclic Disulfide Molecular Junctions with Two Different Adsorption States at the Contact: A Density Functional Theory Study

Jang

Goddard

2008

J. Phys. Chem. C

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1,2-Dithiolane is a promising anchor group for attaching molecules to metal electrodes in molecular junction devices. This five-membered cyclic disulfide adsorbs on Au surfaces either in a cyclic fashion (with its disulfide bond intact, via molecular adsorption) or in an acyclic fashion (with its disulfide bond broken, via dissociative adsorption). Our density functional theory calculations show that the dissociative adsorption is slightly preferred, but both are stable. We also report nonequilibrium Green's function calculations showing that molecular junctions of cyclic and acyclic 1,2-dithiolanes sandwiched between two gold electrodes exhibit essentially the same insulating current-voltage characteristics at moderate bias voltages, despite the significant difference in their states of adsorption.

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Section: Resultsmentioning

confidence: 99%

Electron Transport through Cyclic Disulfide Molecular Junctions with Two Different Adsorption States at the Contact: A Density Functional Theory Study

Jang

Goddard

2008

J. Phys. Chem. C

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“…1A, from published UV absorption and x-ray and neutron diffraction data, for the compounds listed in the legend to Fig. 1A; for thioctic acid and dimethyl disulfide, the dihedral angles were obtained from x-ray (23) and microwave (22) data, respectively, and the UV absorption spectra were measured here. The diffraction and UV data of the compounds studied here are summarized in Table 1.…”

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confidence: 99%

Disulfide Bond Dihedral Angles from Raman Spectroscopy

Wart

Lewis

Scheraga

et al. 1973

Proc. Natl. Acad. Sci. U.S.A.

169

103

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Raman spectra of several compounds containing the CS-SC moiety were obtained (in the solid phase) from 450-800 cm-' to investigate the S-S and C-S stretching behavior. The S-S stretching frequency varied linearly with the CS-SC dihedral angle (obtained from either x-ray or neutron diffraction or ultraviolet absorption) for compounds whose CC-SS dihedral angles were not very different. The ratio of the intensities of the S-S and C-S stretching bands exhibited no recognizable correlation with either the CS-SC dihedral angle or the CSS bond angle, probably because this ratio is sesisitive to the crystalline environment. The linear dependence of the S-S stretching frequency on dihedral angle leads to a dihedral angle for the plant hormone, malformin A, that is in excellent agreement with that estimated from the longest wavelength CS-SC ultraviolet absorption band.The disulfide bond is an important structural feature of many important biological molecules. The CS-SC moiety occurs in antibiotics such as gliotoxin, sporidesmin, and acetylaranotin in the form of an S-S bridged piperazinedione system in which the CS-SC dihedral angle is severely restricted by ring closure (1, 2). Hormones, such as oxytocin (3), vasopressin (4), and malformin (5), contain disulfide bonds (cystine) that can assume conformations with widely varying dihedral angle, depending upon ring size and other structural constraints. In globular proteins, such as ribonuclease, chymotrypsin, lysozyme, carboxypeptidase, etc., packing requirements may result in dihedral angles that vary substantially from the widely accepted value (6) of about 900 for L-cystine in aqueous solution. In chymotrypsin, for example, this angle varies from 87°-126°(7). It is, therefore, of considerable importance to have a method that can provide information about this dihedral angle both in solid state and in aqueous solution. Raman spectroscopy appears to be a suitable technique for this purpose, since the Raman spectra of compounds containing disulfide bonds usually show welldefined bands that arise from C-S and S-S stretching modes (8,9), and these vibrations might be sensitive to the CS-SC dihedral angle.Absorption spectra can also be used to obtain information about CS-SC dihedral angles, since the relationship between this dihedral angle and the longest-wavelength CS-SC absorption frequency in the ultraviolet is well established both theoretically (10) and experimentally (see references cited in ref. 10). However, this method for determining CS-SC dihedral angles is limited to simple systems in which the UV absorption spectrum is free from nondisulfide-related transitions from about 250 to 380 nm. Many systems (proteins for example, which contain aromatic residues) have nondisulfide chromophores that absorb in this region, and thus prevent study of the CS-SC absorption bands. On the other hand, as t To whom requests for reprints should be addressed. 2619has been pointed out (8, 9), these compounds (including proteins) exhibit S-S and C-S stretching bands in a reg...

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“…5. Within the experimental deviation, the SeS bond length in 1 is similar to that found in lipoic acid (2.053(4)) [27]. The Cp rings are almost perfectly parallel.…”

Section: X-ray Crystallographymentioning

confidence: 52%