Perylene bisbenzimidazole nonlinear dielectric material for energy storage.

A novel perylene bisbenzimidazole comprising both donor and acceptor functional groups was designed, synthesized, and characterized. This structure exhibits potentially useful physical properties, including a nonlinear dielectric response to an increasing electric field. This material can be used in energy storage devices as the dielectric part of a capacitor. Energy storage devices based on film capacitors are targeting applications in a wide range of industrial, residential and transportation systems.

Alkyne Benzannulation Reactions for the Synthesis of Novel Aromatic Architectures.

Aromatic compounds and polymers are integrated into organic field effect transistors, light-emitting diodes, photovoltaic devices, and redox-flow batteries. These compounds and materials feature increasingly complex designs, and substituents influence energy levels, bandgaps, solution conformation, and crystal packing, all of which impact performance. However, many polycyclic aromatic hydrocarbons of interest are difficult to prepare because their substitution patterns lie outside the scope of current synthetic methods, as strategies for functionalizing benzene are often unselective when applied to naphthalene or larger systems. For example, cross-coupling and nucleophilic aromatic substitution reactions rely on prefunctionalized arenes, and even directed metalation methods most often modify positions near Lewis basic sites. Similarly, electrophilic aromatic substitutions access single regioisomers under substrate control. Cycloadditions provide a convergent route to densely functionalized aromatic compounds that compliment the above methods. After surveying cycloaddition reactions that might be used to modify the conjugated backbone of poly(phenylene ethynylene)s, we discovered that the Asao-Yamamoto benzannulation reaction is notably efficient. Although this reaction had been reported a decade earlier, its scope and usefulness for synthesizing complex aromatic systems had been under-recognized. This benzannulation reaction combines substituted 2-(phenylethynyl)benzaldehydes and substituted alkynes to form 2,3-substituted naphthalenes. The reaction tolerates a variety of sterically congested alkynes, making it well-suited for accessing poly- and oligo(ortho-arylene)s and contorted hexabenzocoronenes. In many cases in which asymmetric benzaldehyde and alkyne cycloaddition partners are used, the reaction is regiospecific based on the electronic character of the alkyne substrate. Recognizing these desirable features, we broadened the substrate scope to include silyl- and halogen-substituted alkynes. Through a combined experimental and computational approach, we have elucidated mechanistic insight and key principles that govern the regioselectivity outcome of the benzannulation of structurally diverse alkynes. We have applied these methods to prepare sterically hindered, shape-persistent aromatic systems, heterocyclic aromatic compounds, functionalized 2-aryne precursors, polyheterohalogenated naphthalenes, ortho-arylene foldamers, and graphene nanoribbons. As a result of these new synthetic avenues, aromatic structures with interesting properties were uncovered such as ambipolar charge transport in field effect transistors based on our graphene nanoribbons, conformational aspects of ortho-arylene architectures resulting from intramolecular π-stacking, and modulation of frontier molecular orbitals via protonation of heteroatom containing aromatic systems. Given the availability of many substituted 2-(phenylethynyl)benzaldehydes and the regioselectivity of the benzannulation reaction, naphthalenes can be prepared with control of the substitution pattern at seven of the eight substitutable positions. Researchers in a range of fields are likely to benefit directly from newly accessible molecular and polymeric systems derived from polyfunctionalized naphthalenes.

Rapid access to substituted 2-naphthyne intermediates via the benzannulation of halogenated silylalkynes.

Aryne intermediates are versatile and important reactive intermediates for natural product and polymer synthesis. 2-Naphthynes are relatively unexplored because few methods provide precursors to these intermediates, especially for those bearing additional substituents. Here we report a general synthetic strategy to access 2-naphthyne precursors through an Asao-Yamamoto benzannulation of ortho-(phenylethynyl)benzaldehydes with halo-silylalkynes. This transformation provides 2-halo-3-silylnaphthalenes with complete regioselectivity. These naphthalene products undergo desilylation/dehalogenation in the presence of F- to generate the corresponding 2-naphthyne intermediate, as evidenced by furan trapping experiments. When these 2-naphthynes are generated in the presence of a copper catalyst, ortho-naphthalene oligomers, trinaphthalene, or binaphthalene products are formed selectively by varying the catalyst loading and reaction temperature. The efficiency, mild conditions, and versatility of the naphthalene products and naphthyne intermediates will provide efficient access to many new functional aromatic systems.

Diazatetracenes Derived from the Benzannulation of Acetylenes: Electronic Tuning via Substituent Effects and External Stimuli.

Functionalized diazatetracenes are prepared using a new two-step sequence. The use of a dichlorobenzaldehyde in a Cu-catalyzed benzannulation of acetylenes provides functionalized dichloronaphthalenes that afford diazatetracenes using Buchwald-Hartwig aminations. This approach provides unique substitution patterns and rapid access to covalently linked dimeric diazatetracenes. Their electronic properties are characterized by UV-vis absorption/emission and cyclic voltammetry, revealing strong effects from both external stimuli by acid and internal substituent effects.

Rapid synthesis of crowded aromatic architectures from silyl acetylenes.

Congested aromatic systems were prepared by benzannulating silyl-protected arylacetylenes. The silyl groups may be retained in the naphthalene products and transformed into iodides in high yield. The desirable attributes of this strategy, particularly its remarkable tolerance of sterically hindered alkynes, are showcased in the efficient synthesis of a congested, branched oligo(naphthalene). As such, benzannulations of diaryl and silyl-protected acetylenes show outstanding promise for accessing new aromatic architectures.