Hexaarylbenzene: Evolution of Properties and Applications of Multitalented Scaffold

Abstract

The easily rotatable peripheral aromatic rings around central benzene in hexaarylbenzene (HAB) derivatives create a very intriguing nonplanar, propeller-shaped geometry. Because of the very low susceptibility toward self-aggregation, HAB derivatives are much stronger candidates among various polyphenylenes/hetero-oligophenylenes when poor molecular cohesion and inefficient packing is required. However, the native properties of hexaphenylbenzene (HPB) can be varied by proper tailoring and substitution of the HAB core. The cohesion and packing in the structures of HAB aggregates induce effective structural variations so as to modify the fundamental features. Recently, HAB derivatives attracted a lot of research interest because of their significant role as liquid crystalline materials, organic light-emitting diodes, photochemical switches, redox materials, and molecular receptors. Herein, detailed attention is given to the pioneering work based on synthetic optimization of different HAB cores, elaborated study of their crystal engineering, various interesting applications of HAB derivatives, and future possibilities and capabilities of this still underexplored scaffold.

Scope of the Thermal Ring‐Expansion Reaction of Boroles with Organoazides

“…Nevertheless, it is interesting to note that all aryl substituents, including the thienyl group on boron, are arranged in a propeller‐like fashion around the central ring, indicating no significant conjugation between them . A striking aspect of the molecular structure of 11 is the nearly perpendicular orientation of the aryl ring substituents relative to the central azaborinine, which is in stark contrast to the commonly observed preference for a propeller‐like arrangement enabling π–π interactions between all of the aromatic groups at the periphery (see Figure S5 in the Supporting Information) . The observed change in conformation is most likely due to the differently polarized π system of the pentafluorophenyl group disrupting the toroidal conjugation …”

Multiple‐Porphyrin Functionalized Hexabenzocoronenes

“…[45] a) Ph 2 O, 260 8C, mW; b) Ni(acac) 2 ,toluene, 110 8C; c) Co 2 (CO) 8 [31] was synthesized in al iterature-known statistical porphyrin condensation and reactedw ith tetracyclone 2 [40,42] to the mono-porphyrin-HPB 3. [31,38] The transformation to the respective HBC derivative 6 workeda lmost quantitatively using FeCl 3 as the oxidant. To lane-porphyrin 1 is further suitable for the preparation of tri-porphyrin-substituted HPBs.…”

“…Hexaphenylbenzenes (HPBs) and their oxidized derivatives hexa‐ peri ‐hexabenzocoronenes (HBCs) have received tremendous attention during the past 20 years in materials chemistry, for example in molecular electronics and nonlinear optics . They have proven to be a suitable scaffold for catalytic applications, the design of supramolecular architectures, as well as a perfectly sized template for the preparation of nano‐ring and nano‐ball structures.…”

“…Hexaphenylbenzenes (HPBs) and their oxidized derivatives hexa-peri-hexabenzocoronenes (HBCs)h ave received tremendous attention during the past 20 years in materials chemistry, for example in moleculare lectronics and nonlinearo ptics. [1][2][3][4][5] They have provent obeasuitable scaffold for catalytic applications, [6,7] the design of supramolecular architectures, [8,9] as well as ap erfectly sized template fort he preparation of nanoring [10,11] and nano-ball [12] structures.I nc ontrast, porphyrins and related macrocycles,w hich are foundi nn ature in different appearances such as heme, chlorophyll,o rb acteriochlorophyll, have attracted the attention from the scientific community ever since their discovery.D ue to their photophysical charac-teristics, featuring high extinction coefficients in the visiblelight region, porphyrins have provent ob ea ni deal chromophoref or light-harvesting architectures. [13][14][15][16][17][18][19][20][21] Thec ombination of both buildingb locks, porphyrins and HPBs, was initiated in 2002 by the synthesis of aH PB core, surrounded by six directly meso-attached porphyrins.…”

Templated deprotonative metalation of polyaryl systems: Facile access to simple, previously inaccessible multi-iodoarenes

“…Novel methods to improve the preparation of functionalized multiarenes for these applications are continuously being sought. Reflecting the importance of developing new methods to access novel polyaryl systems, Suzuki et al ( 32 ) have recently reported the elegant synthesis of a new class of “multitalented” hexaarylbenzenes ( 33 ) that contain five or six different arene substituents on a single benzene molecule.…”