Pentagon‐Containing Doublet Graphene Fragments with Edge‐Dependent Spin/Charge Distribution

Abstract

The synthesis of stable open-shell hydrocarbon system comprising of pentagon defects and zigzag edges remains unexplored, which can be considered as model compounds for unraveling the spin-localized states in graphene edges. With concise synthetic approaches, two π-extended fluorenyl radicals were synthesized and isolated in their crystalline state. X-ray crystallographic analysis and studies on the magnetic, optical and electrochemical properties of neutral and charged species have revealed an interesting edge-dependence of the spin/charge distribution, that is, the spin and charge distribution shifted from the pentagon defects to the zigzag edges with the elongation of conjugation. Such phenomenon was unprecedented for hydrocarbon radicals and can be rationalized by the recovery of Clar Sextets in the dominant resonance structures. Remarkably, one of the radicals exhibited exceptional stability in air-saturated solutions with the half-life time up to 260 d, thus providing opportunities for the applications as electronic materials.

S-Shaped Helical Singlet Diradicaloid and Its Transformation to Circumchrysene via a Two-Stage Cyclization

“…On the basis of our previous molecular and synthetic design, an S-shaped doubly helical singlet diradicaloid 1 was designed to have an intermediate diradical character, helicity, and aligned reactive centers for ring cyclization. The synthetic route is outlined in Scheme : a 2-fold Suzuki coupling reaction between 6,12-bis­(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)­chrysene 5 and 4-bromophenanthrene-3-carbaldehyde 4 afforded compound 6 , which further underwent nucleophilic addition with mesitylmagnesium bromide, followed by ring closure by BF 3 ·Et 2 O to produce key intermediate 7 .…”

Synthesis and structure elucidation of triarylmethyl radicals with anthryl substitution

“…1b, the spin would mainly distribute at the anthryl unit in the folded structure and at the TAM site in the twisted structure. Lately, the dependence of spin distribution of hydrocarbon radicals on conjugation 11 and edge structures 12 has been revealed; however, it is not clear how a folded and twisted structure would influence the spin distribution. Here, we report the synthesis of two stable TAM radicals 8a and 8b with one or two anthryl groups, and the investigation of their structures, spin distributions and physical properties.…”