Spirobifluorenes

Star-shaped molecules with oligophenyl arms derived from 9,9-spirobifluorene as the central unit have been synthesized by Tour et al. [58] and Salbeck et al. [59] and have been suggested as potential emitter materials for blue LEDs. 

The authors used a synthesis of 9,9-spirobitluorenes 32 which was developed by Clarksen and Gomberg [60] and which includes the addition of biphenyl-2-yl-magnesium iodide to fluorenone and subsequent cyclization with protic acids. To obtain 2,2,, 7,7 -arylated 9,9-spirobifluorenes 33, 9,9-spirobifluorene (32) was tetrabrominated [58] to yield 34 followed by a Suzuki-type aryl-aryl cross-coupling with various oligoaryl and oligoheteroaryl boronic acids to obtain the 2,2, 7,7 -tetraarylated derivatives 33. 

Crystal structure of 9,9 -spirobifluorene Csoregh, I., Czugler, M., Weber, E. Unpublished result (1985)... 

The low efficiencies could be due to lack of intimate contact (interface) between the sensitizer (which is hydrophilic) and the spirobifluorene (which is hydrophobic). Moreover, the surface charge also plays a significant role in the regeneration of the dye by the electrolyte.98 In an effort to reduce the charge of the sensitizer and improve the interfacial properties between the surface-bound sensitizer and the spirobifluorene hole-carrier, amphiphilic heteroleptic ruthenium(II) complexes ((48)-(53)) have been used as sensitizers. These complexes show excellent stability and good interfacial properties with hole-transport materials, resulting in improved efficiencies for the solar cells. 

A blue OLED with a very low turn-on voltage of 2.7 V and a luminance of 500 cd/m2 at 5 V with structure ITO/Spiro-TAD/Spiro-PBD/Al Mg has been reported. The robust and morphologically stable spirobifluorene-cored pyrimidine oligoaryl blue emitter... 

Prelog and co-workers (160, 161) chose 9,9 -spirobifluorene as a starting material for synthesizing chiral crown ethers since (i) it has a more rigid carbon skeleton than the 1,1 -binaphthyl unit, and (ii) it can be substituted easily in the 2 and 2 positions by electrophilic reagents. Thus, the 2,2 -diacetyl derivative (Figure 19) obtained after a Friedel-Crafts on 9,9 -spirobifluoiene can be con-... 

Very recently, the synthesis of a series of chiral poly(9,9 -spirobiflu-orene)crown ethers [e.g., (SS)-139, (SSSS)-140, (SSSSSS)-141, and (S55SSS5S)-142] with 26-, 52-, 78-, and 104-membered rings have been described (162). The last three are rare examples of compounds with C4, 5, and Cg synunetries, respectively. They were isolated chromatographically from a reaction mixture consisting of (S)-2,2 -bisbromomethyl-9,9 -spirobifluorene, ethylene glycol, KOr-Bu, and Csl in tolune. 

Figure 19. The synthesis of crown compounds containing racemic and chiral 9,9 -spirobifluorene units.

The signs of the exciton-split Cotton effect reflect the absolute configuration of the molecule if the direction of the transition moment in the chromophore is established. For example, chiral 9,9 -spirobifluorene derivative 1 has R configuration as indicated by a strong positive CD couplet (A = +1111.7) due to the LBb band of the anthracene chromophores, the electric transition moment of which is polarized along the long axis of the chromophore (Figure 14)100... 

Becker et al. (5) prepared polymeric organic light-emitting diodes by copolymerizing 4,7-dibromobenzo[l,2,5]-thiadiazole, (IV), and 4,7-dibromobenzo-furazone, (V), with spirobifluorene derivatives. Polymerizations were performed under Yamamoto conditions. 

Conjugated polymers containing spirobifluorene and fluorene units,... 

Title Conjugated Polymers Containing Spirobifluorene Units and Use Thereof... 

Research Focus Preparation of optoelectronic devices using copolymers containing spirobifluorene derivatives. 

Originality Electroactive modified polymeric spirobifluorene derivatives are... 

Preparation of 2,7-dibromo-8 -f-butyl-5 -(4"-f-butylphenyl)-2, 3 -bis(2-methylbutyloxy)spirobifluorene (S-US1)... 

A Schlenk flask was charged with Ni(COD)2 (5.57 mmol) and 2,2 -bipyridyl (5.57 mmol) and then 25 ml of dimethylformamide and 80 ml of toluene were added. The mixture was heated to 80°C and after 30 minutes treated with 1,5-cyclooctadiene (3.51 mmol) and a solution of a selected spirobifluorene (2.11 mmol) and a selected comonomer (0.242 mmol) dissolved in 20 ml of toluene added. After 144 hours the... 

Spirobifluorene monomers and spirobifluorene copolymers are provided in Tables 1 and 2, respectively. 

TABLE 1. Selected Spirobifluorene Monomers Prepared in Three Reaction Steps for Subsequent Conversion into Spirobifluorene Copolymer by Yamamato Coupling... 

TABLE 2. Spirobifluorene Copolymers Prepared by Yamamoto Coupling of... 

Tsai et al. (2) determined that blue phosphorescent organic light-emitting devices consisting of 2,2 -bis(A,A-disubstituted amino)-9,9 -spirobifluorenes, (I), were effective as hole transporting materials and had efficiencies of up to 16%, 30.6 cd/A and 26.7 lm/W. 

Low cost alternatives to inorganic p-type semiconductors can be found in organic species and conductive polymers. Organic hole conductors like the spiro-compound 2,2, 7,7 -tetrakis(/V,/V-di-/)-methoxyphenyl-amine)-9,9,-spirobifluorene (OMeTAD) (Fig. 17.41) have demonstrated some promise for application in dye-sensitized... 

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