ISSN:
0377-0486
Schlagwort(e):
Chemistry
;
Analytical Chemistry and Spectroscopy
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
The infrared and Raman spectra of methylviologen (1,1′-dimethyl-4,4′-bipyridine dication, MV2+) have been measured from both the solid dichloride and aqueous solutions. The preresonance behaviour of MV2+ Raman bands showed that the absorption at ˜196 nm is mainly responsible for the resonance scattering process in MV2+. In the region below 1700 cm-1, nine polarized (p˜1/3) resonance Raman bands of the methylviologen radical cation, MV+, were assigned to in-plane ring modes. Arguments are given that the chromophore of MV+ may also partially include the methyl groups. The excitation profiles of the MV+fundamentals, measured with laser wavelengths covering the range 350.6-676.4 nm, reveal three main groups of modes, each behaving differently for the excitation in this range. Modes containing largely ν(C—C) ring contributions are mainly coupled with electronic transitions at ˜395, ˜605 and ˜720 nm and yield simple excitation profiles. Modes involving principally the vibrations of the N+—CH3 group show complicated interference peaks in the whole range of the excitation profiles. γ(CCC) is mainly coupled with the absorption at ˜620 nm. Resonance Raman bands of the (MV+)2 dimer have been characterized through studies of the concentration dependence of the spectra.
Zusätzliches Material:
8 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/jrs.1250120107
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