Electronically Stabilized Nonplanar Phenalenyl Radical and Its Planar Isomer

Abstract

Stable phenalenyl radicals have great potential as the basis for new materials for applications in the field of molecular electronics. In particular, electronically stabilized phenalenyl species that do not require steric shielding are molecules of fundamental interest, but are notoriously difficult to synthesize. Herein, the synthesis and characterization of two phenalenyl type cations is reported: planar benzo[i]naphtho[2,1,8-mna]xanthenium (8 + ) and helical benzo[a]naphtha-[8,1,2-jkl]xanthenium (9 + ) which can be reduced to the corresponding radicals. Radical 9 represents the first stable, helical phenalenyl radical which does not rely on bulky substituents to ensure its stability. Both cations are water-soluble and the radicals are stable for weeks at room temperature under air. These compounds were characterized crystallographically, and also by NMR, EPR, electrochemistry and electronic spectra. The synthesis of the previously reported compound benzo [5,6]naphthaceno[1,12,11,10-jklmna]xanthylium (5 + ), the largest oxygen-containing polycyclic hydrocarbon, was undertaken for comparison with 8 + and 9 + , allowing us to report its crystal structure here for the first time. The different properties of these compounds and their radicals are explained by considering their differing aromaticities using in-depth computational methods.

Persistent, highly localized, and tunable [4]helicene radicals

“…Electronic structure analysis revealed that the spin density is mostly delocalized across the phenalenyl and pyrilinium moieties. 38 Importantly, while the crystal structures of air-stable triaryl porphyrin [4]helicene radicals 35 and some heteroatom-centered [4]helicene radicals are known, 39,40 the structure of metal-free carbon-centered [4]helicene radical has not been obtained (although the structure of the diamagnetic precursor of radical IV from Scheme 1 is available 37 ).…”

Design of Open‐Shell π‐Conjugated Microporous Polymer Film with Super‐High Conductivity

“…Dimer of other phenalenyl radicals was reported previously from the experiments, including eclipsed dimers, [29] staggered dimers, [26,29] as well as parallel displaced dimers. [27,35] These dimer conformations were also considered in this paper. Herein, eclipsed and staggered conformations were mainly investigated, which are two possible stable conformations.…”

Boron–Nitrogen‐Doped Nanographenes: A Synthetic Tale from Borazine Precursors

“…Aiming at enhancing the yield of soluble borazinocoronene 2,w er easoned that the hexafluoro-functionalized isomer of molecule 5,b earing an ortho fluoride leaving group on each of the N-and B-aryl rings, could lead to cascade-type electrophilic aromatic substitution events through stepwise CÀCb ond formation.I ti sd uring these synthetic investigationst hat we could isolate the first boroxadizine-doped PAHf eaturing ag ulf-type peripherya nd prove its structure through singlec rystal X-ray diffraction analysis. Propelled by these findings,wed ecided to investigate further the doping effecto ft he boroxadizine unit and prepared all-carbon and pyrylium [42][43][44][45] PAHa nalogues, all featuring a gulf-type [46] periphery.A so bserved for the case of molecule 2, the replacement of the central benzene ring by its B 3 N 2 Oc ongener widens the HOMO-LUMO gap and it enhances the fluorescence quantum yield. Xylyl moieties were introduced to favor solubility.…”