Carbazole Oligomers Research Articles

A Cyclic Carbazole Oligomer for Electroluminescence Applications

Abstract A novel cyclic carbazole oligomer, which contains the EL chromophore in the main-chain, for organic light-emitting diodes is described. The device structure of glass substrate/indium tin oxide/hole transport layer/cyclic oligomer (electron transport layer)/Al was employed. The EL device exhibited green light with a luminance of 60 cd/m2 at 15 V.

Monolithic carbazole oligomer exhibiting efficient photorefractivity

A multifunctional conjugated carbazole trimer has been designed as a monolithic photorefractive material. The photorefractive properties of this carbazole trimer were demonstrated by a two-beam coupling experiment at a wavelength of 532 nm. An asymmetric energy transfer between the two beams has been observed. A relatively large two-beam coupling net gain coefficient and a four-wave mixing diffraction efficiency have been obtained.

Multifunctional Carbazole Oligomer for Monolithic Photorefractive Materials.

We have developed a novel multifunctional chromophore for photorefractive applications. This chromophore, a carbazole oligomer, possesses all the properties required for photorefractivity. Furthermore, because of its good film forming properties, it can be used for optical image processing. The photocarrier generation properties of this chromophore and its second-order nonlinear optical response in acceptor-substituted carbazoles were examined by xerographic discharge, second-harmonic generation, and electro-optic measurements. Photorefractivity was measured directly by two-beam coupling and four-wave mixing experiments.

Novel Molecules for Photorefractive Application

Abstract Monolithic multifunctional chromophores have been developed as a new class of organic photorefractive materials. Oligomeric carbazole molecular systems in the form of starburst dendrimers and conjugated trimers were studied. Molecular solids of acceptor-substituted carbazole oligomers and dendrimers exhibit glass transition. The second-order nonlinear optical coefficients d ij were determined to be 50 pm/V by second-harmonic generation measurements. We also examined the photoconductive properties by the xerographic discharge method. Two beam coupling and four-wave mixing experiments were performed to characterize photorefractivities. The photorefractive phase shift measurement indicated that the induced index grating is shifted by 90[ddot] with respect to the absorption grating. Unlike usual photorefractive polymers containing multi-component systems these multifunctional chromophores can be applied to monolithic photorefractive materials.

The Structural Elucidation of Oligomeric Blue Dyes Derived from 9‐Alkylcarbazoles

AbstractCarbazoles react with a variety of one‐carbon fragments at the 3‐ or 3,6‐positions to give di‐ and trimeric products with CH2: links. These precursors react by losing hydride ion to give blue oligomeric dyes. Carbazoles substituted in the 9‐position by CH2SPh, CH2SOPh, and CH2SO2Ph rearrange to give carbazole oligomers linked at the 3,6‐positions. Products are characterised spectrally, and their mechanism of formation is discussed.

Application of Gel Permeation Chromatography for Investigation of 9-(2, 3-Epoxypropyl)-Carbazole Oligomers

Abstract Gel permeation chromatography on dextran gels “Sephadex LH-2O” and “Sepnadex LH-60” in the solution of dimethyl formamide was used for the estimation of molecular weight and molecular weight distribution of 9-C2, 3-epoxypropyl)carbazole oligomers and for the investigation of the process of their obtaining as well. The simple numerical method of the instrumental dispersion correction as well as the principle of “the differential chromatograms” was used to interpret the gel permeation chromatography data. The method used permits to separate 9-(2, 3-epoxypropyl)carbazole oligomers within the range of molecular weights 150–15000.

Polaromicrotribometric (PMT) and IR, ESCA, EPR spectroscopic study of colored radical films formed by the electrochemical oxidation of carbazoles: Part I. Carbazole and N-ethyl, N-phenyl and N-carbazyl derivatives

Under certain experimental conditions, the electrochemical oxidation of carbazole in a CH 3CN medium yields radical films which are stable. The formation of these films has been followed in situ by PMT, and their structure has been determined by IR, ESCA and EPR spectroscopy. In the medium without pyridine, the formation of adherent dark-green films (type I films) on a Pt or Au electrode is detected as soon as the potential reaches 0.8 V/Ag−Ag +. Reduction with sodium dithionite bleaches the color and yields a new film which has the structure of 3,3′-dicarbazyl. In the medium with pyridine, the films detected at comparable potentials are brownish (type II films) and more passivating than type I films, and are comparable to films obtained by the direct oxidation of 9,9′-dicarbazyl; they correspond to carbazole oligomers bound both by the 9,9′ nitrogen atoms and the 3,3′ carbon atoms. Both type I and type II films display paramagnetic properties caused by the presence of carbazole cation radicals associated with the ions of the supporting electrolyte (ClO 4 − or BF 4 −).

Polaromicrotribometric (PMT) and IR, ESCA, EPR spectroscopic study of colored rdical films formed by the electrochemical oxidation of carbazoles Part I. Carbazole and N-ethyl, N-phenyl and N-carbazyl derivatives

Under certain experimental conditions, the electrochemical oxidation of carbazole in a CH3CN medium yields radical films which are stable. The formation of these films has been followed in situ by PMT, and their structure has been determined by IR, ESCA and EPR spectroscopy. In the medium without pyridine, the formation of adherent dark-green films (type I films) on a Pt or Au electrode is detected as soon as the potential reaches 0.8 V/Ag−Ag+. Reduction with sodium dithionite bleaches the color and yields a new film which has the structure of 3,3′-dicarbazyl. In the medium with pyridine, the films detected at comparable potentials are brownish (type II films) and more passivating than type I films, and are comparable to films obtained by the direct oxidation of 9,9′-dicarbazyl; they correspond to carbazole oligomers bound both by the 9,9′ nitrogen atoms and the 3,3′ carbon atoms. Both type I and type II films display paramagnetic properties caused by the presence of carbazole cation radicals associated with the ions of the supporting electrolyte (ClO4− or BF4−).