Aggregation-induced emission of [3]cumulenes functionalized with heptagon-containing polyphenylenes

Abstract

Turning on the fluorescence of [3]cumulenes: we report the luminescence at room temperature upon aggregation of [3]cumulenes functionalized with propeller-like heptagon-containing polyphenylenes. These endgroups turn on the emission of a [3]cumulene by steric protection and restriction of their intramolecular rotations in the aggregates.

Construction of Heptagon‐Containing Molecular Nanocarbons

“… [74] In one notable example, the cyclization reaction of diyne 76 and alkyne 77 resulted in heptagon‐embedded polyphenylene 78 , which can undergo oxidative cyclization under Scholl reaction conditions to afford fully cyclized heptagon‐containing HBC 79 . Through the installation of different substituents, various derivatives of 78 and 79 have been obtained, many of which featured promising optoelectronic properties including low band gaps and long fluorescence lifetimes [75–81] …”

“…Very recently,t he same group successfully synthesized heptabenzo[7]circulene (75), an egatively curved nanographene containing seven adjoined [4]helicene units (Scheme 20). [69] Thes ynthesis involved ring expansion of cyclic ketone 70 followed by triflation to afford 71,which was subjected to Diels-Alder cycloaddition with isobenzofuran 72 to provide cycloadduct 73.T his underwent oxygen bridge cleavage and rearomatization to give 74,which was subjected to the final DDQ-mediated Scholl reaction, yielding the desired product 75.X -ray diffraction analysis on racemic crystals revealed that compound 75 has at wisted saddle topology with approximate C 2 symmetry.T he [7]circulene moiety seen in 75 with asaddle depth of 1.73 is more curved than [7]circulene itself (saddle depth 1.10 )b ecause the [4]helical substructure in 75 induces agreater degree of steric clash.…”

Combining Defects in a Single Nanographene: A Fully Helical Saddle Ribbon

“…By following this strategy, we have synthesized various structures containing seven-membered rings, such as nanoribbons 12c or [3]cumulenes derivatives. 20…”

Photo- and Thermal Interconversion of Multiconfigurational Strained Hydrocarbons Exhibiting Completely Switchable Oxidation to Stable Dicationic Dyes

“…Extended -conjugated molecules have been widely investigated for their unique physical properties that can be modified by proper molecular design. In particular, much attention has been focused on sterically congested and/or curved polycyclic aromatic hydrocarbons (PAHs) [1][2][3][4][5][6][7][8][9][10][11][12][13][14] as well as cyclic -conjugated molecules like cycloparaphenylenes [15][16][17][18][19][20][21] and carbon nanobelts. [22][23][24] These highly strained molecules are potential candidates with special characteristic features that are not found in normal compounds.…”

“…Within such compounds, curved structures for PAHs are efficiently induced by incorporating mediumsized rings, such as seven-membered rings, which impart molecular strain and distortion. 3,4,7,8,10,11,13 For example, we recently reported that highly strained hydrocarbons could be generated by connecting two dibenzocycloheptatriene units with a C-C bond, in which a sevenmembered ring is a key structure to induce severe strain to give a hyper covalent bond with a C-C single bond length beyond 1.8 Å. 25 Such an elongated bond can be cleaved upon two-electron oxidation to give the corresponding stable dication [dynamic redox (dyrex) behavior] to exhibit electrochromic behavior.…”