Keita Hyodo

Selective Synthesis of Multisubstituted Olefins Utilizing gem- and vic-Diborylated Vinylsilanes Prepared by Silylborylation of an Alkynylboronate and Diborylation of Alkynylsilanes

The synthesis of a series of gem- and vic-diborylated vinylsilanes was accomplished via highly selective transition-metal-catalyzed syn-dimetalation to the alkynylmetal species. This protocol served as a general synthetic method toward regio- and stereodefined multisubstituted olefins. The key steps are the diastereoselective Suzuki-Miyaura cross-coupling reactions of gem- and vic-diborylated vinylsilanes, in which the two boron groups showed discrete reactivities to afford diverse precursors of multisubstituted olefins.

Diborylation of alkynyl MIDA boronates and sequential chemoselective suzuki-miyaura couplings: A formal carboborylation of alkynes

Platinum-catalyzed diborylation of phenylethynyl MIDA boronate with Bpin-Bpin proceeds to yield 1,1,2-triboryl-2-phenylethene with two different classes of the boron functionalities. Sequentially, the obtained 1,1,2-triboryl-2-phenylethene are subjected to Suzuki-Miyaura coupling to introduce a series of aryl groups chemoselectively to afford 1,1-boryl-2,2-diarylethenes.

Phenanthro[1,2-b:8,7-b’]dithiophene: a new picene-type molecule for transistor applications

A new picene-type molecule, phenanthro[1,2-b : 8,7-b’]dithiophene, has been synthesized for use in organic field-effect transistors (OFETs). The molecule consists of a phenanthrene core with two thiophene rings fused on the ends. This molecule can be recognized as a picene analogue. The electronic structure of the molecule was determined by its optical absorption spectrum together with a theoretical calculation based on density functional theory (DFT). The topological and electronic structures of thin films produced by direct thermal evaporation of the compounds and by deposition from a solution were characterized by optical imaging, X-ray diffraction, and atomic force microscopy. FET devices were fabricated with these thin films, and showed field-effect mobility as high as 10−1 cm2 V−1 s−1.

Transistor application of new picene-type molecules, 2,9-dialkylated phenanthro[1,2-b: 8,7-b′]dithiophenes

Field-effect transistors (FETs) have been fabricated with thin films of a series of 2,9-dialkylated phenanthro[1,2-b:8,7-b′]dithiophene derivatives (Cn-PDTs). The FET characteristics of Cn-PDT thin-film FETs with an SiO2 gate dielectric as well as high-k gate dielectrics were recorded, and the dependence of the field-effect mobility, μ, on the number (n) of carbon atoms in the alkyl chains was investigated, showing that the 2,9-didodecylphenanthro[1,2-b:8,7-b′]dithiophene (C12-PDT) thin-film FET displays superior properties, with μs as high as 1.8 cm2 V−1 s−1 for the SiO2 gate dielectric and 2.2 cm2 V−1 s−1 for the HfO2 gate dielectric. The average μ values, 〈μ〉, reach 1.1(5) and 1.8(6) cm2 V−1 s−1, respectively, for the SiO2 and ZrO2 gate dielectrics. Low-voltage operation, showing an absolute average threshold voltage 〈|Vth|〉 of ∼11 V, was implemented, together with the above high 〈μ〉 of ∼2 cm2 V−1 s−1. Also, a flexible FET was fabricated with a parylene gate dielectric. The results of this study show the potential of the C12-PDT molecule for application in a high-performance transistor.

Bis[1]benzothieno[2,3-d:2′,3′-d′]anthra[1,2-b:5,6-b′]dithiophene: synthesis, characterization, and application to organic field-effect transistors

We report the straightforward synthetic method and characterization of bis[1]benzothieno[2,3-d:2′,3′-d′]anthra[1,2-b:5,6-b′]dithiophene (BBTADT) having nine aromatic rings fused without solubilizing groups. The highest mobility of fabricated OFETs utilizing BBTADT exhibited 2.7 × 10−2 cm2 V−1 s−1 in polycrystalline films formed by vapor deposition, depending on the annealing temperatures of a substrate.

Transistor Properties of 2,7-Dialkyl-Substituted Phenanthro[2,1-b: 7,8-b′]dithiophene

A new phenacene-type molecule with five fused aromatic rings was synthesized: 2,7-didodecylphenanthro[2,1-b:7,8-b′]dithiophene ((C12H25)2-i-PDT), with two terminal thiophene rings. Field-effect transistors (FETs) using thin films of this molecule were fabricated using various gate dielectrics, showing p-channel normally-off FET properties with field-effect mobilities (μ) greater than 1 cm2 V−1 s−1. The highest μ value in the thin-film FETs fabricated in this study was 5.4 cm2 V−1 s−1, when a 150 nm-thick ZrO2 gate dielectric was used. This implies that (C12H25)2-i-PDT is very suitable for use in a transistor. Its good FET performance is fully discussed, based on electronic/topological properties and theoretical calculations.