| Abstract
| - Hybrid density functional theory (DFT) calculations at the B3LYP/cc-pVDZ level have beenperformed on a series of heterobuckybowls, 3X, C18X3H6 (X = O, NH, CH2, BH, S, PH, PH3, Si,SiH2, and AlH). The minimum energy conformations and the transition states for bowl-to-bowlinversion, where the geometry is bowl shaped, are computed and characterized by frequencycalculations. The geometries of heterotrindenes, 2X, C12X3H6 (X = O, NH, CH2, BH, S, PH, PH3,Si, SiH2, and AlH), were obtained, and the bond length alternation (Δ) in the central benzenoidring shows remarkable sensitivity as a function of substituent with a wide range of fluctuations(−0.014 to +0.092 Å). The Δ computed in 2BH was found to be comparable with the highest bondalternation reported to date in benzenoid frameworks. The inversion dynamics of these heterobowlsand their bowl depths were fit to a mixed quartic/quadratic function. The size of the heteroatomseems to exclusively control the bowl depth and rigidity as well as the synthetic feasibility. Incontrast, the bond length alternation seems to be controlled by electronic factors and not by thesize of the substituted atom either in trindenes or in heterosumanenes. The thermodynamic stabilityof this class of compounds is very much comparable with trithiasumanene (3S), which has beensynthesized recently. The chemical hardness (η) was measured to assess the stability of theheterosumanenes. The strain energy buildup in a sequential ring closure strategy along twosynthetic routes, namely a triphenylene route and a trindene route, were explored, and the trindeneroute was found to be highly favorable for making such compounds compared to the triphenyleneroute. However, in both routes the ease of the synthetic feasibility increases as the size of theheteroatom increases.
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