From branched hydrocarbon propellers to C3-symmetric graphite disks.
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.
Wu
Jishan
J
Max-Planck Institut für Polymerforschung, Ackermannweg 10, Mainz 55128, Germany.
Tomović
Zeljko
Z
Enkelmann
Volker
V
Müllen
Klaus
K