Carbazole-containing solutions

The negative influence of excimer formation has to be taken into consideration for the molecular design of new polymers having high carrier generation efficiency and effective carrier transport. Ledwith et al. have concluded that carbazole-containing polymers do not exhibit excimer emission except when the carbazole chromophores are directly bound to the polymer backbone [61]. This conclusion was corroborated by the investigation of the photophysical properties of dilute solutions of a number of polymers [62-64]. 

Purification of anthracene. Dissolve 0-3 g. of crude anthracene (usually yellowish in colour) in 160-200 ml. of hexane, and pass the solution through a column of activated alumina (1 5-2 X 8-10 cm.). Develop the chromatogram with 100 ml. of hexane. Examine the column in the hght of an ultra-violet lamp. A narrow, deep blue fluorescent zone (due to carbazole, m.p. 238°) will be seen near the top of the column. Immediately below this there is a yellow, non-fluorescent zone, due to naphthacene (m.p. 337°). The anthracene forms a broad, blue-violet fluorescent zone in the lower part of the column. Continue the development with hexane until fluorescent material commences to pass into the filtrate. Reject the first runnings which contain soluble impurities and yield a paraffin-hke substance upon evaporation. Now elute the column with hexane-benzene (1 1) until the yellow zone reaches the bottom region of the column. Upon concentration of the filtrate, pure anthracene, m.p. 215-216°, which is fluorescent in dayhght, is obtained. The experiment may be repeated several times in order to obtain a moderate quantity of material. 

The combination of thiophene and thiophene-51,S -dioxide units in a copolymer allows tuning the emission color from green to pure red [407,549], However, the PLEDs fabricated with these materials showed a rather low 4>el< 0.01% that further decreased with an increasing number of thiophene units. Similar results (significant decrease of the PL QE) were observed for thiophene thiophene-5,5-dioxide copolymers containing 3,6-dimethoxyfluorene (449 [303]) and carbazole units (450 [550]) (d>PL = 20-25% in solution). 

Various more complex dyes of industrial significance contain more than one carbazole system. For example, Cl Vat Orange 11 (6.86) contains two carbazole components and a central unit derived from 1,5-diaminoanthraquinone. This dye is prepared by carbazolisation of the trianthrimide produced when two moles of 1-chloroanthraquinone react with one mole of 1,5-diaminoanthraquinone. The equivalent isomeric dye obtained from 1,4-diamino-anthraquinone is reddish brown (6.87 Cl Vat Brown 1). The interesting, symmetrically-substituted tetracarbazole dye Cl Vat Green 8 (6.88) was first synthesised in 1911 by Hepp from 1,4,5,8-tetrachloroanthraquinone. Not surprisingly, the product (C70H28N4Oio relative molecular mass 1084) is of very low solubility. The structure was confirmed in 1957 by Jayaraman, who found no evidence of uncyclised anthrimides in the UV spectrum of the dye solution in concentrated sulphuric acid [32]. 

Rather different are two N-alkylations effected with mercuric acetate 9-(3-oxobut-l-yl)carbazole (29 R = CH2CH2COCH3) was formed from car-bazole and but-l-en-3-yne in ethanolic solution containing a trace of concentrated sulfuric acid/° and a low yield of 9-allylcarbazole was produced on reaction with allyl alcohol in benzene... 

A flask was charged with the step 1 product (3.0 gm) dissolved in 300 ml of 1,4-diox-ane and then treated with carbazole-9-carbonyl chloride (0.9 mmol) and methacryloyl chloride (2 mmol). Triethylamine (2 mmol), 4-dimethylaminopyridine (0.2 mmol), and hydroquinone (10 mg) were then added and the reaction mixture stirred at 60°C for 6 hours. The polymer solution was filtered and the polymer precipitated in diisopropyl ether three times. The product was isolated as an off-white solid containing... 

Electrochemical doping of insulating polymers has been attempted for polyacetylene, polypyrrole, poly-A/-vinyl carbazole and phthalocyaninato-poly-siloxane. Significantly, Shirota et al. [91] claim to have achieved the first synthesis of electrically conducting poly(vinyl ferrocene) by the method of electrochemical deposition (ECD) [91]. This is based on the insolubilization of doped polymers from a solution of neutral polymers. A typical procedure applied [91] for polyvinyl ferrocene is to dissolve the polymer in dichlorometh-ane and oxidize it anodically with Ag/Ag+ reference electrode under selective conditions. The modified polymer [91] (Fig. 28) is a partially oxidized mixed valence salt containing ferrocene and ferrocenium ion pendant groups with C104 as the counter anion. 

Crude anthracene (about 40%) is mixed in a vessel fitted with a mechanical stirrer, with 1J times its weight of benzol or solvent naphtha (90% at 160°) this specification means that 90% by volume distils up to 160°. Sodium nitrite to one-tenth of the weight of crude anthracene taken is dissolved in 10 times its weight of water, and sufficient 10% sulphuric acid (7-2 gms. for each 1 gm. of 10% nitrite) to decompose this quantity of nitrite is added to the benzol—anthracene mixture and the temperature maintained at 25°. The nitrite solution is then run in at such a speed that no red fumes escape. When all the solution has been added the mixture is filtered at the pump. The filtrate consists of two layers, one of sodium sulphate solution and one of solvent naphtha, or benzol containing the impurities such as nitroso-carbazol. The purified anthracene on the filter is washed with benzol or solvent naphtha this latter on a large scale is used for the final treatment of a fresh lot of crude anthracene. The initial benzol or solvent naphtha, after separation from the aqueous solution, is recovered by distillation. The anthracene from this treatment will be about 80% pure. It may be purified to 95% by crystallising from heavy bases (pyridine, etc.), and is finally raised by sublimation and re-crystallisation from benzol to 98%. (For the estimation of purity, see p. 497.) (C. T., 23, 8, 21 D.R.P., 122852.)... 

Similar results (a significant decrease of the photoluminescence quantum yields) were observed for thiophene-thiophene-S,S-dioxide copolymers containing 3,6-dimethoxyfluorene 560 (03MM8986) and carbazole 561 (02MM8413) (with 0F = 20-25% in solution). 

Carbazole forms a persistent nitroxyl (13) when a solution in benzene containing di-tert-butyl peroxide is photolyzed 471 The radical had been observed earlier in both isotropic and nematic liquid phases and the radical has been theoretically described.573,574... 

Early methods of separation employed such solvents as oleic acid/ crude coal-tar solvent naphtha, light pyridine,5 etc. Based on the selective solution of phenanthrene by the coal-tar naphtha, and of carbazole liy the light pyridine, Clark proposed a complicated scheme for the separation and recovery of all three of these constituents. Recently, organic liquid compounds containing the furan nucleus have been found to have a highly selective solvent action on phenanthrene and carbazole." Thns, furfural while dissolving phenanthrene and carbazole does not have a marked solvent action on anthracene at low temperatures. However, at elevated temperatures it does dissolve anthracene with the result that it is possible... 

Intermolecular energy transfer from one polymeric material to another while the molecules are in solution or in the melt can also take place [17]. This was demonstrated on an intramolecular excimer and exiplex formation in solutions of polyesters containing naphthalene or carbazole moieties in their chemical structures [98]. 

In addition to the reactions mentioned above, there are others of this type that are used in detecting and determining specific classes of carbohydrates. The carbazole-sulfuric acid method has been much used in analysis of uronic acids and acidic polysaccharides, which give a weaker response than neutral sugars in the other methods. The presence of borate ions decreases interference by proteins and salts, increases color yield, and reduces the time required for color development. In a recommended procedure for manual analysis, the sample solution (containing 0.02-0.2 [tmol of uronic acid) is mixed (1 5, v/v) with a solution of sodium tetraborate (25mmol 1 ) in concentrated sulfuric acid and the mixture is heated at 100°C for 10 min. After rapid... 

A similar effect (decrease in the PL efficiency, pl = 20-25 % in solution) was observed for thiophene-thiophene-5, 5 -dioxide copolymers containing 3,6-dimethoxyfluorene (120 [163]) and carbazole units (121 [164]). 

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