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From Branched Hydrocarbon Propellers to C3-Symmetric Graphite Disks

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posted on 06.08.2004, 00:00 authored by Jishan Wu, Željko Tomović, Volker Enkelmann, Klaus Müllen
Branched hydrocarbon propellers (9 and 12) were prepared by stepwise palladium-catalyzed Hagihara−Sonogashira coupling reactions and Diels−Alder cycloadditions and submitted to oxidative cyclodehydrogenation by FeCl3 to afford two new giant graphite disks 2 and 3 with 3-fold symmetry in high yield. One of the precursors, the polyphenylene dendrimer 9 containing 150 carbon atoms, was crystallographically characterized. The poorly soluble graphite disks were characterized by isotope-resolved MALDI-TOF mass spectroscopy, and their electronic and vibrational properties were investigated by solid-state UV−vis and Raman spectroscopy. The effect of molecular size and geometry on their properties was discussed. The molecule 2 represents the largest, 3-fold-symmetric all-benzenoid graphite disk, and the five-membered rings in molecule 3 open the opportunity to synthesize large bowl-shaped PAHs.

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