Synthesis, Structural, and Photophysical Properties of the First Member of the Class of Pyrene‐Based [4]Helicenes

Abstract

A convenient route to a new class of pyrene‐based [4]helicenes is presented. Wittig reaction of 7‐tert‐butyl‐1,3‐dimethyl‐5‐formylpyrene with benzyltriphenylphosphonium salts in the presence of nBuLi afforded 7‐tert‐butyl‐1,3‐dimethyl‐5‐(phenylethenyl)pyrenes, from which 4,5‐naphthalene annulated aromatic [4]helicenes, namely 7‐tert‐butyl‐1,3‐dimethyl‐13‐methoxydibenzo[ij,no]tetraphene and 7‐tert‐butyl‐1,3,12,14‐tetramethyldibenzo[ij,no]tetraphene, were obtained by photoinduced intramolecular cyclization. The chemical structures of these [4]helicenes were determined on the basis of their elemental analyses and spectroscopic data. The helicity in the synthesized [4]helicene induced by the presence of the second methyl group in the fjord region is discussed in detail. The photophysical and electrochemical properties of these newly developed [4]helicenes were fully investigated by UV/Vis absorption and photoluminescence spectrphotometry, and cyclic voltammetry (CV), and the crystal structures were determined for two examples.

Deep-blue electroluminescence from nondoped and doped organic light-emitting diodes (OLEDs) based on a new monoaza[6]helicene

“…1(a)) comprising carbazole and phenanthrene moieties possessed long and short characteristic C-C bonds. 39 C-C bonds with an average of 1.428(4) Å in the inner helical rim of the Fjord region, namely C20-C15 (1.401(3) Å), C15-C8 (1.434(3) Å), C8-C9 (1.423(4) Å), C9-C10 (1.445(4) Å), C10-C11(1.459(4) Å), C11-C27 (1.401(4) Å) increased by 0.033 Å relative to the average bondlength 1.395(3) Å of those in aromatic compounds. In contrast, their counterparts with the average of 1.343(5) Å in the peripheral six-member rings, that is C17-C18 (1.368(4) Å), C30-C29 (1.331(5) Å), C22-C23 (1.342(5) Å), C25-C26 (1.331(5) Å), C13-C14 (1.344(5) Å), decreased by 0.052 Å compared to the average bond-length of those in aromatic compounds.…”

Chimerical Pyrene‐Based [7]Helicenes as Twisted Polycondensed Aromatics

“…There is an inspiring theoretical study on wide helical aromatics,9 but only a limited number of helicenes having additional aromatic units (usually one or two benzene rings) fused to their outer rim have been described 10. As far as merging pyrene and helicene scaffolds is concerned, there are, to the best of our knowledge, only a few examples of pyrene‐based helicenes so far published, by Collins et al.,11a Yamato et al.,11b, c Bock, Durola et al 11d. and others 11e.…”

Functionalization of Pyrene To Prepare Luminescent Materials—Typical Examples of Synthetic Methodology

“…However, the product yield can be much improved (to 70 %) by prolonging the reaction time and adding large amounts of iodine and propylene oxide . Similarly, ( E )‐ 24 can be functionalized to the corresponding [4]helicenes 30 in good yields by intramolecular photocyclization . This approach opened the door to the preparation of more attractive pyrene‐based extended π‐conjugation PAHs.…”