Oligo absorption

The optical absorption spectra and the first reduction potentials are virtually independent of the number of pyrene units present in the molecule, as a result of the specific stereoelectronic situation. Since the orbital coefficients of the bridgehead centers are almost zero, the rings are electronically decoupled. Thus, oligopyrenes differ significantly from oligo(pflrfl-phenylene)s (OPVs). 

As mentioned above, poly(9,10-anthrylenevinylene) is not accessible by means of the Wessling polymerization procedure. Well defined oligo(9,10-anthrylene-vinylene)s (111) were synthesized via Horner-type coupling [132]. Extrapolation of the optical absorption energies in the 111 series against the corres-... 

H. Anger, E. Walzel and B. Kahrmann, About the absorption of oligo-galacturonides from caecum of rats. FASEB Meeting (1994), Anaheim/USA Abstr. FASEB J. 8 (1994) A152. 

Deoxy-L-threo-hexos-5-ulosuronic acid (10), the product of the action of oligo-D-galactosiduronate lyase, shows no absorption at 235 nm therefore, its activity is estimated on the basis of the decrease in ultraviolet absorption at this wavelength, using unsaturated di(D-galactosiduronic acid) as the substrate. 

Exposure to periodate yields 3-formylpyruvic acid, which reacts with thiobarbituric acid, giving rise to red condensation products having an absorption maximum at 545-550 nm. Certain workers have used the thiobarbituric acid test without previous oxidation of the unsaturated oligo-D-galactosiduronates with periodic acid.3-29,239,260 Even here, the products of reaction with thiobarbituric acid have an absorption maximum at 550 nm. 

By competitively inhibiting the alpha-glucosidase enzymes in the mucosa cells of the small intestine these agents suppress the breakdown of di-, oligo-and polysaccharides into monosaccharides and thus decrease carbohydrate absorption. In this way postprandial elevations of blood glucose levels can be prevented or diminished. 

Fig. 4 Absorption spectra of radical cations of oligo-phenylenevmylenes OPV of different chain lengths in CH2CI2 solution. Cj and C2 denote the transitions indicated in Fig. 2a. The radical ions are generated by adding SbCl5 as an oxidant to the solution. From [37] with permission. Copyright (1993) by Elsevier...

Poly(a-phenylethyl isocyanide), however, yields complex products distinguishable from monomer upon thermal degradation at 20 mm Hg (13). At 300° C a viscous condensate is produced which is free of isocyanide absorption in its infrared spectrum and appears very similar to the recently synthesized oligo-isocyanides, a,co-dihydrotri(a-phenylethyl isocyanide) and a,co-dihydrohexa(a-phenylethyl isocyanide) (15). Pyrolysis at 500° C produces an intense broad infrared absorption band in the range about 3300 cm-1, which is the range of associated N il bonds. Pyrolysates obtained at 700° C reveal nitrile absorption at 2270 cm"1, that becomes more intense in pyrolysates produced at temperatures up to 1300° C. A slow pyrolysis at 200-300° C is indicated for the study of primary structural changes in poly(a-phenylethyl isocyanide). Pyrolysates of poly(<7-... 

The band occurring at about 345 nm could be assigned to absorptions involving the spider legs, as suggested by the extinction coefficient values s which are linearly dependent on the number of bithienyl pendants present in the molecule (2, 4, and 6). The extinction coefficient is known to be dependent upon the number of the thiophene units also in linear a-oligo thiophenes. 

Oligo(thienylene-ethynylene) derivatives were obtained linked with [60]fullerene. A typical compound showed absorptions at 641 and 704 nm and emission at 716 and 798 nm (01T6877). 

Some other 3-thienyl ether derivatives have been prepared. Poly[3-oligo(oxyethylene)-4-methyltiophene] showed an absorption peak at 550 nm (95JCS(CC)2293). On the other hand, poly[3-(N-succinimido(tetra-ethoxy)oxy)-4-methylthiophene] was prepared and it is able to react with amines to give the corresponding carbamate with a 15-crown-5 attached substructure. This polymer showed absorption at 429 nm and fluorescence at 543 nm (04T11169). 

Optical absorption, PL and EL in poly[(tetraalkyldisilanylene)-/>-oligophenylene]s (PDSiOP) were found to depend on the length of the oligo-phenylene and not on the length of the short alkyl substituents, such as methyl and ethyl groups.76... 

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