UV-vis-near-IR absorption spectrum

The UV-vis-near-IR absorption spectrum of the solution of the protonated polymer exhibits MLCT bands and valence tautomerization similar to those of 1,8-Fc2Aq as shown in Fig. 3.32, indicating the formation of fulvene complexes in the main chain in solution. Infrared spectrum of the protonated polymer also shows the similarity with that of l,8-Fc2Aq, namely, half the CC triple bond remains. 

Fig. 3.32 UV-vis-near-IR absorption spectrum of protonated (l,r-Fc-l,8-Aq) (1.3 X 10 mol dm as Fc-Aq monomer unit) in acetonitrile.

The UV-Vis-near-IR absorption spectral change of FcCHCBQH in acetonitrile, on stepwise addition of CF3SO3H (0-100 eq), indicated an interesting proton response, as shown in Figure 13b. The new intense bands appearing at 400 and 456 nm, the molar extinction coefficients, e values, of which were estimated at 4.0 X 10 and 2.5 X lO mol dm cm, respectively, were appreciably similar to those of the free semiquinone radical," " and the weak shoulder band at 600 nm with 8 = 350 mol dm cm" can be attributed to the E2g -> Eiu transition of the ferrocenium ion. The EPR spectrum of the frozen solution of the product at 6.4 K exhibited a well-resolved signal (g = 3.97, = 1.64) attributable to a ferrocenium... 

Figure 2.1 Ultraviolet (UV)-visible (Vis)-near-IR absorption spectra of 12 purified semiconducting SWNTs and the starting HiPco-produced SWNT mixture (SWNTsHiPco)- The structure of each purified SWNT species (viewed along the tube axis) and its n, m) notation are given at the right side of the corresponding spectrum. The baseline level of each spectrum was offset to facilitate visual comparison. Reprinted by permission from Macmillan Publishers Ltd." ...

The ruthenium oligothienylacetylide complexes 93 (Chart 5.30) [106] and the oligothienylferrocene complexes 94a and b were electrochemically polymerized [107]. The voltammetry of poly-94a and poly-94b films contains redox waves due to both the ferrocene and backbone redox couples. Low-energy absorption bands appear upon oxidation of both the Fe centers and the conjugated backbone in the UV-Vis-near-IR spectrum of the films, and these have been attributed to charge-transfer processes. The poor solubility of 94b prevents electropolymerization at room temperature however, polymer films can be prepared at elevated temperatures. Electropolymerization of 95, in which hexyl chains have been added to increase the monomer solubility, has also been reported [108]. 

Ketenes absorb near 2100-2130cm . When the photolysis was carried out and the IR spectrum of the solution monitored, it was found that a band appeared at 2118 cm , grew, and then decreased as photolysis proceeded. The observation of this characteristic absorption constitutes good evidence for a ketene intermediate. As with UV-VIS spectroscopy, the amount of intermediate that can be detected depends both on the intensity of the absorption band and the presence of interfering bands. In general, IR spectroscopy requires somewhat higher concentration for detection than does UV-VIS spectroscopy. 

Optical and FTIR instrumentation. Absorption spectra were taken on three instruments. A Hewlett Packard 8450 UV/Vis Spectrophometer was used for the visible region of the spectrum. This instrument was computer control led and used to measure standard absorption spectra as well as absorption difference spectra. A Cary 14 Spectrophotometer was used for the near IR region, and an IBM IR/90 Series... 

Similar oxidative coupling [Cu(OAc)2/pyridine/dbu, 40 °C] of Fe(C=CC=CH)(dppe)Cp gives Fe(dppe)Cp 2 r-(C=C)4 (159) as an air- and thermally-stable burnt-orange compound.307 Oxidation with [FcH]+ gave forest-green [ Fe(dppe)Cp 2( r-C8)]+ which has two v(CC) absorptions at lower frequencies (1784, 1879 cm-1), intermediate between the diyndiyl and cumulenic forms. The UV/vis spectra contain MLCT bands at 389, 481 nm (neutral) and 403, 423, 556, 624, 707 nm (cation), while the near IR spectrum contains a narrow intense intervalence CT band... 

Three major infrared absorptions occur in the carbonyl stretching region near 2014, 2005, and 1982 cm (cyclohexane) and the molar absorptivi-ties at these positions are 86, 22, and 2.7 L g cm S respectively. The metal-hydrogen stretching absorptions are at 1882 cm" for the hydride and 1313 cm for the deuteride (cyclohexane). A singlet is observed in the HNMR spectrum at d —5.88 (hexane). The gas-phase IR and Raman spectra as well as the UV-Vis spectrum have also been reported. 

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