Hyperbranched Poly phenylene Derivatives

Kim and Webster [57] were the first to show that trifunctional benzene-based monomers can also be used to synthesize poly(phenylene)s, in this case hyperbranched structures 31 based on 1,3,5-trisubsfituted benzene cores. They self-condensed l,3-dibromophenyl-5-boronic acid leading to the formation of soluble, hyperbranched PPP-type macromolecule 31. 

The transformation of the hydrophobic periphery composed of bromo substituents into a hydrophilic wrapping of carboxylic acid functions was achieved by reacting 31 with (i) w-butyllithiimi and (ii) carbon dioxide. The polymer-analogous transformation provides water soluble, amphiphilic derivatives of 31 which constitute useful covalently bonded unimolecular models for micellar structures. 

2 01igo(phenylene)s Composed of Orthogonally Arranged Arms 

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-spirobifluorenes 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 crosscoupling with various oligoaryl and oligoheteroaryl boronic acids to obtain the 2,2, 7,7 -tetraarylated derivatives 33. 

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