9.9- Diarylfluorenes

The first oxetane-functionalized emitter were pyrene derivatives (Fig. 9.19(b), [46]), however, with very limited performance in OLEDs. Later, a poly(pheny-lene-fluorene)-copolymer was reported, however, without any electroluminescence data (Fig. 9.19(c), [47]). The breakthrough came with a recent report on a crosslinkable class of state-of-the-art spirofluorenes (Fig. 9.19(a), [48, 49]). By incorporating a green- and red-emitting comonomer, it was possible to generate the three primary colors (RGB) necessary for color-display applications. More recent concepts use sterically hindered 9,9 -diarylfluorene blocks to link conjugated oligomers (Fig. 9.19(d), [50]). 

Recently, a new synthetic protocol for synthesis of 9-arylfluorenes or 9,9-diarylfluorenes was reported wherein these products were furnished in good to excellent yields by Pd-catalyzed cross-coupling reactions of fluorene with haloarenes [141]. This synthetic method was also applied in the preparation of aryl-substituted sumanenes. Palladium-catalyzed arylation of sumanene (2) was conducted with l-bromo-2,6-dimethylbenzene, and the desired xylylsumanene 124-xyl was... 

LEST 09] Lin C.-Y., Lin Y.-C., Hung W.-Y. et al, A thermally cured 9,9-diarylfluorene-based triaryldiamine polymer displaying high hole mobility and remarkable arrrbient stability , Journal of Materials Chemistry, vol. 19, no. 22, pp. 3618-3623,2009. 

Spirobifluorenes have been investigated by Salbeck [100] and found to be promising materials for use in blue LEDs, and so some effort has been made to incorporate these units into polymers (Scheme 30). As poly(diarylfluorene)s have proven to be stable blue emitters it comes as no surprise to find that polymers containing spirobifluorenes such as 66 [101] and 67 [102] also produce stable blue emission. A fluorene-spirobifluorene alternating copolymer 68 has been made and was found to give stabler emission than the fluorene homopolymer 16, but green emission was still observed upon heating in air at 150 °C [103]. 

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