Fluorene-carbazole

J. Lu, Y. Tao, M. D iorio, Y. Li, J. Ding, and M. Day, Pure deep blue light-emitting diodes from alternating fluorene/carbazole copolymers by using suitable hole-blocking materials, Macromolecules, 37 2442-2449, 2004. 

Hutchison reported the first ESR spectrum of a metastable phosphorescent state by study of naphthalene oriented in durene crystals.4 Since then, similar spectra have been recorded for several other polynuclear aromatics both oriented in host crystals and randomly suspended in glassy matrices. D values for all these ir,n excited states are quite low, indicating little interaction between the unpaired electrons. Interestingly, D for the quinolines equals 0.10cm"1 just as in naphthalene,197 indicating that the presence of a heteroatom does not necessarily change the ir,w nature of the lowest triplet state very much. A similar conclusion has been reached from a comparison of the ESR spectra of fluorene, carbazole, dibenzofuran, and dibenzothiophene.198... 

Ljubic 1, Sabljic A (2011) CASSCF/CASPT2 and TD-DFT study of valence and Rydberg electronic transitions in fluorene, carbazole, dibenzofuran, and dibenzothiophene. J Phys Chem A... 

The photophysics of triplet excitons in conjugated donor-acceptor copolymers e.g. fluorene, carbazole and thiophene derivatives), and their quenching by molecular ojqrgen were evaluated by transient absorption spectroscopy, and correlated with X-ray diffraction measurements of relative material crystallinity. ... 

As might be anticipated from the behaviour of the parent heterocycles, C-2 of indole, benzo[i]furan and benzo[i]thiophene (Table 13) is shifted to lower field than C-3. However, the shifts for C-2 (O, 144.8 Se, 128.8 S, 126.1 NH, 124.7 Te, 120.8) and C-7a (O, 155.0 Se, 141.3 S, 139.6 NH, 135.7 Te, 133.0) in the benzo[i] heterocycles vary irregularly (80OMR(l3)3l9), and the sequence is different to that observed for C-2 in the parent heterocycles, namely 0>Se>Te>S>NH. Also noteworthy is the upheld position of C-7, especially in indole and benzofuran, relative to the other benzenoid carbons at positions 4, 5 and 6. A similar situation pertains in the dibenzo heterocycles (Table 14), where not only are C-1 and C-8 shifted upheld in carbazole and dibenzofuran relative to the corresponding carbons in dibenzothiophene and fluorene, but similar, though smaller, shifts can be discerned for C-3 and C-6 in the former compounds. These carbon atoms are of course ortho and para to the heteroatom and the shifts reflect its mesomeric properties. Little variation in the carbon-hydrogen coupling constants is observed for these dibenzo compounds with V(qh) = 158-165 and V(c,h) = 6-8 Hz. 

The Pschorr reaction also works with substrates containing a bridge other than oxygen. Thus various tricyclic products containing a biaryl subunit are accessible, e.g. carbazoles and fluorenes. 

Figure 7.23 shows the prototype diazobenzo[Z ]fluorene-based natural products kinamycin A and prekinamycin. The kinamycin A-D family were first isolated from Streptomyces murayamaensis, but the structures were incorrectly characterized as having a cyanobenzo[Z ]carbazole ring. Since the initial discovery of the kinamycins, many new analogues have been discovered from natural sources.88-92... 

Carbazole, A-methylcarbazole, IV-ethylcarbazole, dibenzofuran, dibenzothiophene, fluorene, dibenzo-p-dioxin, phenoxathiin, phenoxazine, phenothiazine, xanthene, biphenyl, naphthalene, phenanthrene, anthracene, and fluoranthene could be transformed by E. coli, [314] which was transformed using a plasmid bearing the carAa, Ac, and Ad genes, and expressing only the carA-encoded proteins. Further work is needed to develop a final biocatalyst and to prove the advantages that this degradative pathway would incorporate in a refining bioprocess. 

In the effort to make pure blue-emitting materials Shim and coworkers [146] synthesized a series of PPV-based copolymers containing carbazole (polymers 95 and 96) and fluorene (polymers 97 and 98) units via Wittig polycondensation. The use of trimethylsilyl substituents, instead of alkoxy groups, eliminates the electron donor influence of the latter and leads to chain distortion that bathochromically shifts the emission (Amax = 480 nm for 95 and 495 nm for 97). In addition, a very high PLQY was found for these polymers in the solid state (64 and 81%, respectively). Single-layer PLEDs fabricated with 95 and 97 (ITO/polymer/Al) showed EL efficiencies of 13 and 32 times higher than MEH-PPV, respectively (see also Ref. [147] for synthesis and PLED studies of polymers 99 and 100) (Chart 2.20). 

Similar PPV-based copolymers with carbazole and fluorene units in the backbone 101 and 102 (and also similar copolymers with oxadiazole substituents 103 and 104) have been synthesized by Ree and coworkers [148], Much lower PL efficiency in films was found in this case for carbazole-containing polymers 102 and 104 (1-4%), when compared to materials prepared by Shim (95 and 96, 59-64%) (Chart 2.21). 

A series of carbazole-3,6-diyl polymers, including homopolymer 537c, alternating carba-zole-oxadiazole and carbazole-fluorene copolymers 541-545 and analogous random copolymers containing all three (carbazole, fluorene, and oxadiazole) units were prepared and... 

As demonstrated in previous sections, the carbazole unit was introduced as a pendant group or as a chain member in major classes of EL polymers such as PPVs (95-105,141,177, 190) and PFs (62, 63, 242-245). A variety of 2,7-carbazole-derived polymers with different conjugated units, such as 2-alkoxy- and 2,5-dialkoxy-l,4-phenylene (549) and l,l -binaphtha-lene-6,6 -diyl (550 [658]), 2,5-pyridine (551), 2,7-fluorene (245 [345,346]), 2,5 -bithiophene (554 [345]), 5,8-quinoxaline (552), quinquethiophene-SjS -dioxide (450 [550]), 2,5-thiophene (553), 2,5-furan (555), and acetylene (556 [659]) were reported by Leclerc and coworkers... 

T. Ahn, S. Song, and H. Shim, Highly photoluminescent and blue-green electroluminescent polymers new silyl- and alkoxy-substituted poly(p-phenylene vinylene) related copolymers containing carbazole or fluorene groups, Macromolecules, 33 6764-6771, 2000. 

Y. Fu, J. Li, S. Yan, and Z. Bo, High molecular weight dendronized poly(fluorene)s with peripheral carbazole groups synthesis, characterization, and properties, Macromolecules, 37 6395-6400, 2004. 

O. Stephan and J.-C. Vial, Blue light electroluminescent devices based on a copolymer derived from fluorene and carbazole, Synth. Met., 106 115-119, 1999. 

CHART 4.25 Chemical structure of electrophosphorescent fluorene copolymers where the holetransporting carbazole units have been introduced in the polymer backbone. 

Later, Yang and coworkers [84] reported similar electrophosphorescent fluorene copolymers 71 and 72, where the hole-transporting carbazole units have been introduced in the polymer backbone (Chart 4.25). Optimizing the polymer structure (comonomer ratio) and the device structure (blending with electron-transporting material PBD 8), the EQE of 4.9% has been achieved. 

J Jiang, C Jiang, W Yang, H Zhen, F Huang, and Y Cao, High-efficiency electrophosphorescent fluorene-alt-carbazole copolymers IV-grafted with cylometalated Ir complexes, Macromolecules, 38 4072 1080, 2005. 

Note Technical grades of naphthalene may contain one or more of the following impurities acenaphthene, benzo[6]thiophene, carbazole, chrysene, fluoranthene, fluorene, naphthacene, phenanthrene, pyrene, pyridine, and tetrazene. 

The currently accepted name for (1) in Chemical Abstracts is dibenzothiophene, although biphenylene, diphenylene, or biphenylylene sulfide are still used, especially in the Russian literature. Occasionally 9-thia-fluorene is used and recently, in one instance, dibenzo[6,d]thiophene. An alternative numbering system for (1) is met with on occasions in which C-4 is taken as C-1, as in carbazole. In the absenee of moleeular diagrams this system must be detected by reference to the chemistry described. For example, in a few dyestuff patents 2,7-diaminodibenzothiophene 5,5-dioxide is referred to and this is obviously the 3,7-diamino compound, also known as benzidine sulfone. 

Dibenzothiophene acts as a 7r-electron donor and readily forms complexes with known electron acceptors. In such cases the electronic spectrum of a solution of the two compounds shows a new absorption band, usually in the visible region. The order of donor strengths of several o,o -bridged biphenyls has been estimated from their respective charge-transfer spectra and found to be carbazole > fluorene > dibenzothiophene >dibenzofuran. Dibenzothiophene forms complexes with tetracy-anoethylene, various polynitro derivatives of fluorenone, > naphthalene-1,4,5,8-tetracarboxylic acid dianhydride, and tetra-methylmic acid. ... 

In the absence of any accurate isomer distribution studies the question of theoretical positional reactivities in dibenzothiophene becomes somewhat meaningless. However, when viewed within the context of the behavior of the related heterocycles dibenzofuran, carbazole, and fluorene, specific studies on dibenzothiophene are more valid. Such studies have been made by Eaborn and co-workers. The rates of cleavage of the four isomeric trimethylsilyldibenzothiophenes (Section VI, H, 2) were studied at 50° using a mixture of methanol and aqueous perchloric acid and compared with the rates of protodesilylation of 2- and 4-trimethylsilyldiphenyl sulfide. The reactivities shown in Fig. 3... 

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