Date of Award
Bachelor of Science
Marina A. Petrukhina
Buckybowls are bowl-shaped aromatic polycyclic hydrocarbons that map onto the surface of fullerene molecules, such as C60 and C70, but lack their full closure. They are revered for their ability to undergo multiple reduction reactions, accepting several electrons, due to their degenerate and low energy LUMO orbitals. Corannulene (C20H10), the smallest buckybowl, is well known for its ability to accept up to four electrons. Many studies have been performed targeting preparation and characterization of corannulene anions using the NMR, ESR and UV-vis spectroscopic techniques. Corannulene has also been found to form a solid adduct with C60 without selectivity in its binding. Dibenzo[a,g]corannulene (C28H14), a larger π-bowl and focus of this work, contains a corannulene ring system with an addition of one peripheral benzene ring on each side. Originally studied as a synthetic precursor for creating carbon nanotube endcaps, C28H14 contains two consecutive low energy LUMO orbitals, making it also capable of accepting up to four electrons. Up until now, only NMR characterizations have been performed on C28H14 anions. My research has resulted in the isolation of the first crystalline products of monoanion and dianion of C28H14 with alkali metal cations and their structural characterization using singe crystal X-ray diffraction technique. Preference of metal binding to the exo surface of C28H14 has been revealed in the contact-ion pair of [Rb(18-crown-6)+][C28H14−]. The first naked dianion of C28H14 was also isolated as its sodium salt, [Na(18-crown-6)(DME)+]2[Na2(18-crown-6)2(DME)2+][C28H142−]2, and characterized in this study. This allowed an evaluation of the bowl shape perturbation upon addition of one and two electrons. Both anions showed only small change in their bowl shape compared to neutral C28H14. The supramolecular assembly of dibenzo[a,g]corannulene with fullerenes has been also investigated in this work by co-crystallization of C28H14 with C60 and C70. Though packing of the C28H14 and C60 molecules paralleled that of C20H10 and C60, a novel arrangement has been found for the solid-state structure of C28H14 and C70. In the latter, selective binding of the endo surface of C28H14 to the exo surface of C70 was observed based on their perfect size and curvature complementarity.
Ferguson, Michael V., "Charging and Self-Assembly of Fullerene Fragments" (2013). Chemistry. 4.