From Corannulene to Indacenopicene: Effect of Carbon Framework Topology on Aromaticity and Reduction Limits

Abstract

The electronic structure, reduction limits, and coordination abilities of a bowl-shaped polycyclic aromatic hydrocarbon, indacenopicene (C 26 H 12 , 1), have been investigated for the first time using a combination of theoretical and experimental tools. A direct comparison with the prototypical corannulene bowl (C 20 H 10 , 2) revealed the effects of carbon framework topology and symmetry change on the electronic properties and aromaticity of indacenopicene. The accessibility of two reduction steps for 1 was predicted theoretically and then confirmed experimentally. Two reversible one-electron reduction processes with the formal reduction potentials at −1.92 and −2.29 V vs Fc +/0 were detected by cyclic voltammetry measurements, demonstrating the stability of the corresponding mono-and dianionic states of 1. The products of the doubly reduced indacenopicene have been isolated as rubidium and cesium salts and fully characterized. Their X-ray diffraction study revealed the formation of tetranuclear organometallic building blocks with the [M 2 (18-crown-6)] 2+ (M = Rb (3) and Cs (4)) cations occupying the concave cavities of two C 26 H 12 2− anions. The coordination of two outside exo-bound rubidium ions is terminated by crown ether molecules in 3 to form the discrete [Rb + 4 (18-crown-6) 3 (C 26 H 12 2− ) 2 ] tetramer. In contrast, the larger cesium ions allow the 1D polymeric chain propagation in 4 to afford [Cs + 2 (18-crown-6) 2 (THF)(C 26 H 12 2−)] ∞ .

Fusing a Planar Group to a π‐Bowl: Electronic and Molecular Structure, Aromaticity and Solid‐State Packing of Naphthocorannulene and its Anions

“…Similarly, LUMO+1 and LUMO+2 are separated by only 0.16 eV. The Δ(HOMO–LUMO) gap of 1 is 3.89 eV, making C 28 H 14 a significantly better acceptor than corannulene (Δ(HOMO–LUMO)=4.71 eV) and comparable to the recently studied indacenopicene, C 26 H 12 (3.65 eV) . At the same time, the LUMO of C 28 H 14 (−2.00 eV) lies notably higher than that of C 26 H 12 (−2.42 eV) but lower than that of C 20 H 10 (−1.77 eV).…”

“…Indeed, it is found to be +7.80 kcal mol −1 for neutral C 28 H 14 , which is lower than that in C 20 H 10 (+9.98 kcal mol −1 ). Next, the charge distribution in C 28 H 14 is less symmetric (Figure ) than that in corannulene . Specifically, two separate negatively‐charged areas (one is localized on the bowl part and the other one is mostly concentrated on the naphtho‐group) can be clearly seen.…”

Site‐Directed Dimerization of Bowl‐Shaped Radical Anions to Form a σ‐Bonded Dibenzocorannulene Dimer

“…Thus, the successful candidate has to be less symmetric compared to such highly symmetric and broadly studied π‐bowls as sumanene (C 21 H 12 , C 3 v ) and corannulene ( C 5 v ) . The latter is known to show delocalization of negative charge and, consequently, spin density over the π‐surface in the reduced states, without notable localization on any specific carbon atom . In this regard, we decided to focus on dibenzo[ a , g ]corannulene (C 28 H 14 , Scheme left) that consists of a central corannulene core fused with two peripheral benzene rings on the rim.…”

Synthesis of Rationally Halogenated Buckybowls by Chemoselective Aromatic C−F Bond Activation

“…Our calculations and measured optical E G values indicate that both bowls can be regarded as wide-band-gap semiconductors.A ss hown recently,p ristine indacenopicene is as oft one-electron acceptor and has suitable HOMO and LUMO energy levels to function as a p-acceptor material for organic electronic applications. [46] Thes mall internal reorganization energy (l i )f or electron transport and enhanced electron affinity of indacenopicene and diindenochrysene cores make them suitable building blocks for novel n-channel semiconductive materials in organic thin-film transistors.…”