Synthesis and Properties of Large Polycyclic Aromatic Hydrocarbons with Planar and Non‐Planar Structural Motifs

Abstract

Implementation of non‐planar aromatic motifs in the molecular design of π‐conjugated materials represents a paradigm shift that is interesting from a fundamental research viewpoint but remains largely underdeveloped. To further facilitate this cause, we report on the synthesis and properties of two large polycyclic aromatic compounds (38 carbon atoms). In one compound the planar π‐system pyrene is linked to bowl‐shaped hydrocarbon corannulene through a C=C bond, which is referred to as “corannulene–vinylpyrene”. Photochemical treatment of this compound results in annulation of both aromatic nuclei and formation of the other large fused structure with ten six‐membered aromatic rings, referred to as “corannulene–benzopyrene”. Photophysical and electrochemical studies reveal that the properties of these two structurally related hybrid materials arise from an extended π‐conjugation between the planar and non‐planar motifs and varies depending upon their molecular structure.

Stack the Bowls: Tailoring the Electronic Structure of Corannulene‐Integrated Crystalline Materials

“…Indeed, DR spectroscopic analysis revealed that corannulene integration resulted in appearance of an additional absorption band (550-650 nm) leading to ab athochromic shift of the absorption profile of over 100 nm in comparison with both the pristine COF and corannulene units.S uch ad rastic change could be attributed to charge transfer (CT) between the covalent organic host and pBmoieties,especially taking into account the electron donating character of the framework functional groups (for example,-OMe) and electron-accepting behavior of corannulene moieties. [22] This fact is in line with the results observed in the case of naphthalene (C 10 H 8 ) and pyrene (C 16 H 10 )integration, both possessing higher-lying LUMOs than that of pB-C 20 H 10 (À2.27 eV in contrast to À1.20 eV (C 10 H 8 ) [28] and À1.48 eV (C 16 H 10 ) [29] ), which did not result in CT band formation. Integration of 1,4-dimethoxybenzene and 1,5-dimethoxynaphthalene exhibiting electrondonating behavior also did not result in CT band formation.…”

Stack the Bowls: Tailoring the Electronic Structure of Corannulene‐Integrated Crystalline Materials

“…Such a drastic change could be attributed to charge transfer (CT) between the covalent organic host and πB moieties, especially taking into account the electron donating character of the framework functional groups (for example, ‐OMe) and electron‐accepting behavior of corannulene moieties . This fact is in line with the results observed in the case of naphthalene (C 10 H 8 ) and pyrene (C 16 H 10 ) integration, both possessing higher‐lying LUMOs than that of πB‐C 20 H 10 (−2.27 eV in contrast to −1.20 eV (C 10 H 8 ) and −1.48 eV (C 16 H 10 )), which did not result in CT band formation. Integration of 1,4‐dimethoxybenzene and 1,5‐dimethoxynaphthalene exhibiting electron‐donating behavior also did not result in CT band formation.…”

Ring-Fused 1,4-Dihydro[1,2,4]triazin-4-yls through Photocyclization

“…These methods are much less useful for the synthesis of larger planar systems. Therefore, we focused on photochemical cyclization methods, such as the Mallory reaction, , which are widely used in preparation of closed-shell polycyclic aromatic systems, , including helicenes, nanographenes, − photoswitches, photochromic materials, , and π-extended corannulenes. − …”