Optically active carbazole containing

Table 3. General properties of optically active carbazole containing homopolymers...

Optically active polymers containing carbazole groups may be synthesised by polymerisation of intrinsically optically active carhazole-containing monomers or by copolymerisation of a variety of optically active co-monomers with nonchiral carbazole-containing monomers. Full details are given and it is concluded that the second method is most useful, not least because it permits a wider variation in polymer backbone structures. V. V. absorption fluorescence emission, NMR, and circular dickroism spectra are reported in detail and help to establish a correlation between photophysical behaviour widi both primary and secondary structural features of the polymers. 

Accordingly for almost a decade the authors have studied, in a systematic way, the synthesis and properties of optically active polymers containing carbazole groups . In the present paper they review and evaluate the relevance of such studies to the interpretation of structural and electronic properties. 

Finally, it is worth noting that optically active polymers containing pendant carbazole units have been prepared by attachment of the carbazole group to chemically activated, optically active macromolecules, such as coisotactic copolymers of chiral a-olefins and p-chloromethyl styrene... 

In 1990, Furukawa et al. described the isolation and structural elucidation of chrestifoline-A (192), -B (193), and -C (194) from the root bark of M. euchrestifolia. The chrestifolines contain l-methoxy-3-methylcarbazole [murrayafoline A (7)] as the common structural subunit, which is linked to the second carbazole via the methyl group at C-3. Chrestifoline-C (194) was isolated from nature in optically active form [aJo —5.6 (c 0.054, CHCI3). However, the absolute configuration is not known (161) (Schemes 2.45 and 2.46). 

The brief presents a systematic study of synthesis of optically active polymers. It discusses in detail about the syntheses of three different types of optically active polymers from helical polymers, dendronized polymers and other types of polymeric compounds. The brief also explains the syntheses of optically active azoaromatic and carbazole containing azoaromatic polymers and copolymers optically active benzodithiophene and optically active porphyrin derivatives. The final chapter of the brief discusses different properties of optically active polymers such as nonlinear optical properties, chiroptical properties, vapochromic behavior, absorption and emission properties, fabrication and photochromic properties. The intrinsic details of different properties of optically active polymers will be useful for researchers and industry personnel, who are actively engaged in application oriented investigations. 

In the visible region, carbazole and azo chromophores containing side chain optically active co-polymers give rise to charge carried via a charge transfer complex of induced intramolecular structure. Due to the photoconductivity which was concerned to hole hopping between the molecular mobility of chromophore and side chain carbazole units affected the mechanism of hole transportation due to macromolecular structure [58]... 

Dissymmetric systems shows exciton splitting of dichroic absorptions and optical activity and photochromic materials having NLO, photoresponsiveness and photorefractivity properties, which occurred due to the presence of azoaromatic and chiral functionalities in the polymers [62]. Finally, novel optically active multifunctional methacrylic copolymers were synthesized, which contained side-chains chiral moieties and linked to a photoconductive carbazolic and to a photochromic azoaromatic chromophores... 

Cyanophenyl)-[3-[9-[2-(2-methacryloyloxy-propanoyloxyethyl] carbazolyl]] diazene [(5)-MLECA] chiral monomer containing the carbazole moiety is a novel optically active photochromic polymer. After study of chiroptical, thermally and spectroscopic properties shows the presence of dipolar interaction characteristics between chromophores and chiral confirmation of prevailing helical hardness for chain segments of macromolecules. 

Essentially there are two major ways in which optical activity may be introduced into synthetic polymers. Most obviously the synthesis and utilization of inherently chiral monomers may be employed. Alternatively, and perhaps more conveniently, a prochiral monomer may be copolymerized with a suitable chiral comonomer. For carbazole-containing polymers both synthetic approaches have been employed. 

The synthetic approach to optically active polymers based on the copolymerization of prochiral carbazole containing monomers with easily available optically active vinyl or vinylidenic comonomers is by far the most convenient route to a large variety of optically active polymers. Accordingly, N-vinylcarbazole and spaced-carbazole containing vinyl monomers 11-14 have been copolymerized with different optically active monomers 15-20. 

In copolymers of NVC with different optically active comonomers a definite contribution derived from the prochiral monomer to the molar optical rotation of the whole polymer, is more or less clearly obtained (Fig. 1). In copolymers containing the carbazole moiety spaced far apart from the polymer backbone no apparent contribution is evidenced. More detailed features of any preferentially dissymmetric conformational structure of the carbazole moieties can be gained through circular dichroism measurements . ... 

Table 4. General properties of copolymers of unsaturated carbazole-containing monomers with optically active comonomers obtained in the presence of different initiators...

Rather unusually, induced circular dichroism in copolymers of N-vinylcarbazole with different optically active monomers is optimized at particular copolymer compositions and hence offers an obvious route to the design of optically active polymer reagents from N-vinylcarbazole. Analogously, the dependence of excimer emission properties in carbazole-containing polymers on the primary structure of the monomeric units and the microstructure of the polymer backbone offers the possibility to design polymeric systems with predictable photoresponses and energy transfer characteristics. 

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