Visible‐Light‐Induced Heptacene Generation under Ambient Conditions: Utilization of Single‐crystal Interior as an Isolated Reaction Site

Abstract

The photo-induced generation of unstable molecules generally requires stringent conditions to prevent oxidation and the concomitant decomposition of the products. The visible-light-induced conversion of two heptacene precursors to heptacene wass tudied. Single crystals of bis-and mono-a-diketone-type heptacene precursors (7-DK2 and 7-DK1,r espectively), were prepared to investigate the effect of precursor structure on reactivity. The photoirradiation of a 7-DK2 single crystal cleaved only one a-diketone group, forminga ni ntermediate bearing ap entacenes ubunit, while that of a 7-DK1 single crystal gave rise to characteristic absorption peaks of heptacene and their increaseinintensity with photoirradiation time, indicating the generation of heptacene withoutd ecomposition. Heptacene productionw as not observed when the precursors were photoirradiated in solution, implying that the single crystal interiorp rovided isolation from the external environment, thus preventing heptacene oxidation.

Pushing the Limits of Acene Chemistry: The Recent Surge of Large Acenes

“…Note added in Proof : Very recently heptacene could be photogenerated from its dicarbonyl precursor within a single crystal inside the protective environment of its precursor [143] …”

Synthesis and Characterization of peri‐Heptacene on a Metallic Surface

“…Both families can exhibit, above certain length, diradical or polyradical character arising from the lateral π-extension of their framework by virtue of the gain of additional Clar sextets (defined as six π-electrons localized in a single benzene-like ring separated from adjacent rings by formal CÀ C single bonds) in their openshell resonance forms, which may partially compensate the energy needed to dissociate a C(sp 2 )À C(sp 2 ) π-bond by providing aromatic stabilization. [6,7] While the solution-based synthesis of pristine higher acenes stabilized on different matrixes has been recently achieved, they exhibit short lifetimes, [8][9][10][11][12] and the attachment of bulky aryl substituents onto the most reactive zigzag edges has been shown necessary to attain a reasonable kinetic stability. [13][14][15][16] In fact, by following this strategy, only recently the solution-based syntheses of 4-PA (peri-tetracene) [13,14] and 7-PA [16] employing the bulky 2,6-dichlorophenyl, mesityl and/or tert-butylphenyl groups at the reactive zigzag peripheries have been afforded.…”

Hysteretic Three-State Redox Interconversion among Zigzag Bisquinodimethanes with Non-fused Benzene Rings and Twisted Tetra-/Dications with [5]/[3]Acenes Exhibiting Near-Infrared Absorptions

“…As a result, [n]acenes are widely used as functional organic materials such as semiconductors, [12][13][14][15] fluorescent probes, [16][17][18] and optoelectronic devices. [19][20][21][22][23][24][25] There are two main approaches to their synthesis 26 (Scheme 1a): elimination of small molecule(s) such as carbon monoxide (CO) from precursors [27][28][29][30] and nucleophilic addition to quinones followed by reductive aromatization. 31,32 However, several problems may arise regarding the solubility and stability of the reaction intermediate with an increase in n.…”