Fluorenes dendrimers

Fig. 5 Typical room temperature TOF hole transient for a first generation bis-fluorene dendrimer film of thickness 300 nm and an electric field of 1.6 x lO V/cm. Also shown is the structure of the dendrimer. From [49] with permission. Copyright (2008) by Elsevier...

A year later, Chou and Shu [316] reported Suzuki coupling of similar alternating fluorene copolymers containing Frechet-type dendrimers as side chains. In contrast to the above... 

SCHEME 2.30 Synthesis of the Frechet-type dendrimer-substituted PFs and fluorene random and alternating copolymers. (From Marsitzky, D., Vestberg, R., Blainey, P., Tang, B.T., Hawker, C.J., and Carter, K.R., J. Am. Chem. Soc., 123, 6965, 2001.)... 

A textbook example for the application of the uncorrelated GDM is the recent study by Gambino et al. on a light emitting dendrimer [49]. The system consists of a bis (fluorene) core, meta-linked biphenyl dendrons, and ethylhexyloxy surface units. ToF experiments shown in Fig. 5 were performed on 300 nm thick sandwich films... 

Gambino S, Samuel IDW, Barcena H, Bum PL (2008) Electric field and temperature dependence of the hole mobility in a bis-fluorene cored dendrimer. Org Electron 9 220... 

The first example of the use of a chiral-core dendrimer as enantioselective receptor in molecular recognition processes was reported by Diederich (see Fig. 4.70). This dendrimer, designated as a dendrocleff, acts as enantioselective receptor for monosaccharides. It bears a central axially chiral 9,9 -spirobi[9H-fluorene] unit which is linked via two 2,6-bis(carbonylamino)pyridine spacer groups, each in 2,2 position, with triethylene glycol monomethyl ether dendrons [14b]. Both... 

Other approaches have involved reduction of interchain interaction either by cross-linking the polymers using vinyl endgroups [ 71 ] or by attaching bulky groups, e.g., dendrimers [72,73] or silsesquioxanes [74,75], as end- or side-groups. There is evidence that reduction of fluorene by calcium cathodes is implicated in the formation of ketone defects during LED operation, and this can be suppressed by introduction of a buffer layer between the polymer and the cathode [76]. 

Keywords Branched molecules Dendrimer Excitonic coupling Fluorene Oligomer Two-photon absorption... 

Junction parameter within the excitonic model Excitonic perturbation matrix element Transition oscillator strength Two-photon absorption transition strength N,N-Diethyl-4-(2-nitroethenyl)phenylamine Oligomer consisting of N monomers V-shape molecule with N monomers on branches g-generation dendrimer with N monomers on branches fluorene-fluorene junction... 

I. D. W. Samuel, S. C. Lo, P. L. Bum, Fluorene-containing dendrimers, Patent application W02004029134. 

They have also prepared polymers with Frechet-type dendrons of generations one to three as side chains by Yamamoto polycondensation (Scheme 59) [226]. A molecular weight of 51000 was obtained for the homopolymer 125 with a first-generation dendrimer attached, but only oHgomers (Mn < lOOOOg/mol) were obtained from polymerisation of the fluorenes... 

Mullen and coworkers have prepared a polymer 129 with a first-generation polyphenylene dendron on the side chain (Scheme 60) [228]. Unlike Fr chet dendrimers, such dendrimers are rigid and shape-persistent. Interestingly, the bulky side chains produced no blue shift in the absorption or emission of the polymer compared with PDAFs such as 89, indicating that there is no increased steric repulsion between adjacent fluorene units. LEDs using this polymer display device characteristics (turn-on voltage, emission efficiency. 

Wong WWH, Jones DJ, Yan C, Watkins SE, King S, Haque SA, Wen X, Ghiggino KP, Hohnes AB (2009) Synthesis, photophysical, and device properties of novel dendrimers based on a fluorene-hexabenzocoronene (FHBC) core. Org Lett 11 975-978... 

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