The experimentally characterized hexamethylbenzene dication C6(CH3)62+ shows a pentagonal-pyramidal structure involving a carbon-capped five-membered ring. The structural characterization of this hypercoordination (or hypervalency) gives rise if the aromatic behavior remains in the resulting pentagon ring. Here, we investigated the induced magnetic field of C6(CH3)62+ to gain a deeper understanding of the resulting non-classical structural situation in a representative pentagonal-pyramidal structure. Our results support the view of a C5(CH3)5−/CCH33+ structure, depicting a π-aromatic pentamethylcyclopentadienyl anion with a 6π-electron kernel, with a capped carbon which does not decrease the characteristic shielding cone property of the aromatic ring. Hence, carbon-capped rings are suggested to retain the aromatic behavior from the former aromatic ring. We expect that the analysis of both the overall magnetic response and NMR chemical shifts may be informative to unravel the characteristic patterns in the formation of hypervalent carbon atoms involving non-classical chemical environments.
Let QT = ω x (0, T), where ω is a bounded domain in ℝn (n ≥ 3) having the cone property and T is a positive real number; let Y be a nonempty, closed connected and locally connected subset of ℝh; let f be a real-valued function defined in QT × ℝh × ℝnh × Y; let ℒ be a linear, second order, parabolic operator. In this paper we establish the existence of strong solutions (n + 2 ≤ p < + ∞) to the implicit parabolic differential equationwith the homogeneus Cauchy-Dirichlet conditions where u = (u1, u2, …, uh), Dxu = (Dxu1, Dxu2, …, Dxuh), Lu = (ℒu1, ℒu2, … ℒuh).
On the Aromaticity and 13C-NMR Pattern of Pentagonal-Pyramidal Hexamethylbenzene Dication [C6(CH3)6]2+: A {C5(CH3)5}−–{CCH3}3+ Aggregate