A geometrically selective bottom-up synthesis of curved nanographenes is described. The synthetic methodology used involves the extension of the π-system of positively curved corannulene by a [4+2] cycloaddition reaction followed by cyclodehydrogenation (Scholl oxidation). By selecting the conditions for the Scholl oxidation, the formation of a sevenmembered ring that also confers negative curvature to the resulting nanographene can be activated, offering two topologically distinct, curved nanographenes from a common precursor. Additionally, the structure−property relationship in these new nanographenes is explored via theoretical, electrochemical, photophysical, Raman, and X-ray crystallographic studies.

Highly stable n-doped conductors based on quinoidal oligothiophenes are achieved. The suitable synergy between intra-and inter-molecular effects dictates the exceptional properties of 2DQQT. Uniquely, its incipient diradical character and cholesteric-like aggregation both enhance electrical conductivity (i.e., 14.0 S cm À1) and unprecedented air stability. At the molecular level, our findings demonstrate that small diradical character and deep LUMO energy levels, lower than À4.6 eV, are conditions suitable for achieving stable n-type doping.

A 139-π-electron nanographenoid radical was obtained by expanding the periphery of a naphthalimide–azacoronene hybrid with a methine bridge. The radical was isolated in the form of its σ-dimer, which was shown to possess a conformationally restricted two-layer structure both in the solid state and in solution. The dimer is cleaved into its parent radicals when exposed to ultraviolet or visible radiation in toluene solutions but is resistant to thermally induced dissociation. Under inert conditions, the radicals recombine quantitatively into the σ-dimer with observable kinetics, but they are oxidized into a ketone derivative in the presence of atmospheric oxygen. Combined structural, spectroscopic, and theoretical evidence shows that the σ-dimer contains a weak C(sp 3 )–C(sp 3 ) bond, but is stabilized against thermal dissociation by a very strong dispersive interaction between the overlapping π surfaces.

At etracyano quinoidal tetrathiophene,h aving ac entral bi (thieno[3,4-c]pyrrole-4,6-dione) acceptor,h as been studied. The recovered aromaticity of the thiophenes produces ad iradical species with cross-conjugation between the inter-dicyano and inter-dione acceptor paths.Adiradical character of y 0 = 0.61 and as inglet-triplet gap of À2.76 kcal mol À1 were determined. Competition between the two crossconjugated paths enhances the disjointed character of the SOMOs and results in the confinement of the diradical to the molecular center,e nabling at hermodynamic diradical stabilization featuring ah alf-life of 262 hours.C ross-conjugation effects have been also addressed in the anionic species (up to aradical trianion).Diradicals based on p-conjugated molecules (i.e., KekulØtype) are of continuous interest in chemistry because of their unique connection with the nature of the chemical bond. [1] In addition, they are in the spotlight of current organic electronic applications. [2] Thed iradical character can be tailored in several ways,such as with the number of pro-aromatic rings or with the inclusion of proper functionalization (Scheme 1). [3] Unfortunately,t he increase of diradical character often sacrifices the chemical stability,t herefore strategies conserving diradical character and improving molecular fatigue are highly welcome.Herein we describe astable cross-conjugated diradical.Te tracyanoquinodimethane oligothiophenes (i.e., quinoidal oligothiophene series, nQT where n = number of thiophenes) are well-known in the field of KekulØ diradicals,and form these diradicals by recovery of the aromaticity on the thiophene rings (Scheme 1). Furthermore,g iven the small aromatic character of thiophene,al arge tunability of the diradical character and of the singlet-triplet gaps (DE ST gaps) is facilitated in nQT. [4,5] In the nQT oligomer series,t he tetramer in Scheme 1i st he first element with evidence of diradical properties. [5] Differently functionalized quinoidal tetramers have been reported with the objective of modifying the solubility and optoelectronic properties. [4,5] However,the evaluation of the diradical character on quinoidal tetramers and its dependence on the substitution and p-electron structure of thiophene has not been addressed in detail yet.Herein, we modify aquinoidal tetracyano tetrathiophene core with thieno[3,4-b]thiophene [6] and thieno [3,4-c]pyrrole-4,6-dione [7] (TPD) groups,f orming 4QT-TPD (Scheme 1). 4QT-TPD has been reported to be amaterial that is easily ndoped and has high chemical stability,h igh electrical conductivity,a nd outstanding thermoelectrical properties. [8] A notable feature of 4QT-TPD is cross-conjugation. Foragiven number of p-bonds,cross-conjugation reduces their effective p-delocalization compared with the case in which all bonds are in linear disposition (linear conjugation). 4QT-TPD thus displays diradical delocalization along two crossed axes of conjugation (Scheme 1), the long axis between the dicyano Scheme 1. Chemical structures of the studied quinoidal ...