Molecular Design of Naphthalene- and Carbazole-Based Monomers for Regiospecific Synthesis of Poly(arylenevinylene)s via Co-Catalyzed Hydroarylation Polyaddition.

This study focuses on the development of regiospecific hydroarylation polyaddition of naphthalene- and carbazole-based monomers with diynes under mild reaction conditions at room temperature. A 1-pyrazole substituent serves as an appropriate directing group for a Co-catalyst to efficiently activate the C-H bonds of generally inactive six-membered aromatic hydrocarbons. The 1-pyrazole groups in 2,6-di(1-pyrazolyl)naphthalene adopt planar conformations and act as directing groups, resulting in a smooth hydroarylation reaction. In contrast, the reaction with 1,5-di(1-pyrazolyl)naphthalene do not proceed. The polyaddition reaction of 2,6-di(1-pyrazolyl)naphthalene selectively proceeds at 3,7-positions under mild reaction conditions at 30 °C, and yields corresponding poly(arylenevinylene) (PAV) with high molecular weight. This molecular design is also applicable to the hydroarylation polyaddition of carbazole; the polyaddition reaction of 9-(2-ethylhexyl)-3,6-di(1-pyrazolyl)carbazole selectively occurred at 2,7-positions. The optical and electronic properties of the synthesized compounds are evaluated. The obtained PAVs serve as an emitting material in organic light-emitting diode (OLED). This study aims to develop a Co-catalyzed hydroarylation polyaddition via C-H activation of generally inactive polyaromatic hydrocarbons (PAHs) under mild conditions.

Regioselective Synthesis of Pyrrole-Based Poly(arylenevinylene)s via Mn-Catalyzed Hydroarylation Polyaddition.

Mn-catalyzed hydroarylation polyaddition of 1-(2-pyrimidinyl)pyrrole (1a) with aromatic diynes is investigated. The use of commercially available MnBr(CO)5 as a precatalyst under the optimized reaction conditions resulted in a site- and regioselective hydroarylation polyaddition, affording the corresponding poly(arylenevinylene)s (PAVs) with excellent vinylene selectivity. The reaction protocol eliminates the production of stoichiometric amounts of byproducts from the monomers. The nonstoichiometric polyaddition of an excess amount of 1a with aromatic diynes is also demonstrated. The 2-pyrimidinyl substituent promoted the intramolecular transfer of the Mn catalyst walking through the 1a moiety.

Synthesis of Pyrrole-Based Poly(arylenevinylene)s via Co-Catalyzed Hydroarylation of Alkynes.

Polyaddition via the Co-catalyzed hydroarylation of 1-(2-pyrimidinyl)pyrrole with aromatic diynes affords poly(arylenevinylene)s under mild conditions. This reaction avoids production of stoichiometric amounts of by-products. Although structural analysis of the obtained polymers reveals the presence of 1,1-vinylidene unit, switching the counter anion of the Co catalyst and steric hindrance of the diyne monomers improves the regioselectivity of the polymers. When a catalyst with bulky counter anions is used for the reaction of less hindered diyne monomers, 1,2-vinylene linkages are formed dominantly over 1,1-vinylidene linkages (93:7). The effect of the regioselectivity of the polymer on the optical and semiconducting properties is also evaluated.