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Auto-oligomerization and hydration of pyrrole revealed by x-ray absorption spectroscopy
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10.1063/1.3223539
/content/aip/journal/jcp/131/11/10.1063/1.3223539
http://aip.metastore.ingenta.com/content/aip/journal/jcp/131/11/10.1063/1.3223539
View: Figures

Figures

Image of FIG. 1.
FIG. 1.

Experimental carbon -edge NEXAFS (green) and ISEELS (red dotted) spectra of gaseous pyrrole with features labeled and a sketch of the molecular structure. The carbons are labeled 1 and 2 to differentiate between the calculated carbon spectra. The calculated carbon 1 fixed nuclei spectrum is shown (blue dots) with the classical MD overlaid (red with shaded error bars) and for carbon 2 the fixed nuclei spectra is shown (purple dots) with the classical MD overlaid (orange with error bars). The experimental ISEELS are from Ref. 19 and the calculated spectra are aligned to the experimental IP of carbon 2, which is shown, as well as that of carbon 1. The calculated spectra are summed to give the total combined carbon -edge spectra shown as summed fixed nuclei (orange dotted) and the summed MD spectra (purple). The arrows indicate corresponding features between theory and experiment.

Image of FIG. 2.
FIG. 2.

Calculated carbon -edge spectra of possible aggregation products are shown. The calculated nonbonded dimer spectrum is shown in blue. The structure of the chemically bonded dimer is shown at the top and its calculated spectrum is shown in both the flat conformation (orange) and when twisted about the carbon-carbon bond formed upon dimerizing (red). The shoulder grows more intense for the trimer (green) and polypyrrole (yellow). The carbons labeled give rise to the large subfeature also labeled .

Image of FIG. 3.
FIG. 3.

Experimental carbon -edge NEXAFS (light green) and ISEELS (red dotted from Ref. 19) spectra of gaseous pyrrole. A 1:1 mixture of the flat pyrrole dimer and the pyrrole monomer (black) captures all the low energy features observed experimentally.

Image of FIG. 4.
FIG. 4.

Experimental carbon -edge NEXAFS of solvated pyrrole at (light green) and (dark green) with features labeled and a drawing of the molecule. The carbons are labeled 1 and 2 to differentiate between the calculated carbon edges. The calculated carbon spectra are obtained from classical MD at 300 K. The carbon 1 spectra are shown (blue with error bars) as are the carbon 2 spectra (red with error bars). The spectra are summed to give the total combined carbon -edge spectrum (purple).

Image of FIG. 5.
FIG. 5.

Experimental nitrogen -edge NEXAFS (green) and ISEELS (red dotted) spectra of gaseous pyrrole and calculated fixed nuclei (purple dashed) and classical MD (blue with error bars) spectra of pyrrole with features labeled and the molecule studied pictured. The average spectrum for classical MD is shown in darker colors and one standard deviation is shown as a lightly shaded line for the classical MD spectra. The experimental IP is shown as a vertical line. The experimental ISEELS is from Ref. 19.

Image of FIG. 6.
FIG. 6.

Experimental nitrogen -edge NEXAFS spectra of pyrrole solvated in water at (orange) and (yellow) and a calculated spectrum at 300 K of the solvated molecule from classical MD (green with error bars) with features labeled. The average spectrum for classical MD is shown in darker colors, with one standard deviation lightly shaded.

Image of FIG. 7.
FIG. 7.

Isosurfaces are shown for the LUMO and of the excited state of pyrrole with and without water, corresponding to 30% of the total integrated value. The nitrogen atom is at the top of the pyrrole molecule in each of these images. These are the transitions that cause the intense first feature of the nitrogen -edge of pyrrole. Part of the reason this feature decreases in intensity upon solvation is due to the mixing of the solvated with the surrounding water molecules. Such mixing is not as strong in the case of the solvated LUMO.

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/content/aip/journal/jcp/131/11/10.1063/1.3223539
2009-09-21
2014-04-25
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Auto-oligomerization and hydration of pyrrole revealed by x-ray absorption spectroscopy
http://aip.metastore.ingenta.com/content/aip/journal/jcp/131/11/10.1063/1.3223539
10.1063/1.3223539
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