Tetrabenzoperipentacene: Stable Five‐Electron Donating Ability and a Discrete Triple‐Layered β‐Graphite Form in the Solid State

Abstract

An oxidative ring-closure reaction of at etranaphthylpyrene derivative led to the synthesis of a5 6a ll-carbon conjugated tetrabenzoperipentacene.I nt he single-crystal Xray structure,t hree molecules make at riple-layered cluster by p-stacking,w herein each layer rotates by 1208 8,a nd is thus considered apetit b-graphite.Asfor the optical properties,the Stokes shift is extremely small (10 cm À1 ), thus indicating its remarkably rigid framework. The tetrabenzoperipentacene exhibits reversible five-electron oxidation waves in cyclic voltammetry,and is regarded as ac ounterpart to the fullerene C 60 in terms of stable multicharge-storage nanocarbon materials. Scheme 1. Resonance structures of aperipentacene.the planes in the unit are about 3.4 , just within van der Waals distances.The layered structure of 1 is the same as that for b-graphite.The rigidity of this carbon sheet was confirmed by the sharp 0-0 absorption band and the remarkably small Stokes shift (only 10 cm À1 ). We observed reversible fiveelectron oxidation waves,t hus revealing the superior redox behavior of the molecular multicharge-storage graphene.

X‐Shaped Polycyclic Aromatic Hydrocarbons: Optical Properties and Tunable Assembly Ability

“…The fluorescencelifetime of 0.79 ns followed asingle exponentiald ecay.S ubstitution of the bromine atoms with electron donating or withdrawing phenyl groups (2a-e)l ed to blue shifts of 3-5 nm of the signals in the absorption and fluorescences pectra ( Figure 3b-d, Ta ble 1);t he fluorescenceq uantum yields and lifetimes both increased to approximately 0.4and 2.65 ns, respectively.T hese compounds showed small Stokes shift ( % 14 nm), which was attributed to the small conformational change in the rigidc onjugated carbon sheet between ground state and excited state. [14] Frontier molecular orbital analysisi ndicated that the highesto ccupied molecular orbital( HOMO) and LUMO were both located on the central di-naphthalohexacene unit, regardless of the nature (electron donating or accepting) of the substituting groups ( Figure 4, Table S3). Time-dependent (TD)-DFT calculations at the B3LYP/6-31G( d, p) level suggestedt hat the low-energy band could be assigned to as ymmetry-allowed HOMO-LUMO transition ( Figure S9, Ta ble S5-13).…”

Solution Synthesis of N = 8 Armchair Graphene Nanoribbons with High Charge Carrier Mobility

“…Compared to 1 and 2, the absorption of 8-AGNR dispersed in 1,2,4-trichlorobenzene highlights an extensive red-shift into the NIR region with a broad absorption peak at 1700 nm (Figure 2d). To exclude the contribution of possible oxidized cationic species, 35,43 like radical cations or dications that could be formed under the Scholl reaction, 8-AGNR was further treated with hydrazine, furnishing a nearly identical spectrum (Figure 2d). Based on the absorption onset, we deduce a record narrow optical bandgap of 0.52 eV for 8-AGNR, in line with the theoretically predicted optical bandgap of 0.42 eV.…”