旭硝子財団助成研究成果報告2018

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28田中　隆行マルチラジカル性有機分子テープの開発15Takayuki TANAKA(2016採択)Development of Tape-like Organic Molecules Exhibiting Multi-radical Character(Project 2016)旭硝子財団　助成研究成果報告（2018）る局所電子移動度を観測した．さらに，測定部位の温度制御システムを開発し，ペンタセン/PMMA界面における局所的な正孔輸送が熱活性化型のホッピング機構により支配されていることを確かめた．また，絶縁層の高分子の種類によりペンタセンの局所電荷輸送特性がどのように影響を受けるか調べ，様々なグレインサイズの試料についてマイクロ波分光を行うことで，ペンタセングレイン内の本質的正孔移動度を15 cm2 V–1 s–1程度，平均トラップ–リリース時間を9.4 psと見積もった．Field-induced time-resolved microwave conductivity (FI-TRMC) technique, developed by the authors, is a noncontact microwave-based method to evaluate the transport properties of charge carriers injected at semiconductor-insulator interfaces by the operation of gate bias voltages. Due to the spatial scale of the charge carrier oscillation by the microwave with 9 GHz frequency, this method provides intrinsic, local-scale mobility values. In this research, in addition to the previous study using p-type organic semi-conductors, evaluations of n-type organic semiconductors under air were demonstrated, revealing the local-scale electron mobility values over 10 cm2 V–1 s–1. Furthermore, the FI-TRMC system with con-tolling temperatures was newly developed. Temperature-dependent study disclosed that local-scale hole transports at pentacene/PMMA interfaces was dominated by the hopping-like mechanism. The size distribution of crystalline grains of pentacene was controlled by using various insulating polymers in metal-insulator-semiconductor (MIS) devices. The relationship between grain sizes and hole mobility values in FI-TRMC were plotted and analyzed by a simple trap-release model, leading to the estimation of intra-grain hole mobility of 15 cm2 V–1 s–1 and averaged trap-release time of 9.4 ps.コロールは４つのピロール環と3つのメチン炭素から構成される環状共役化合物であり，環縮小ポルフィリノイドの1つである．コロールを二量化させテープ状にした化合物（縮環コロールダイマー）は，酸化還元に伴って開核系ジラジカル種と閉殻系の状態を相互変換可能であることが知られていた．近年我々は三重縮環コロールダイマーという新しいテープ状化合物を合成し，そのジラジカル性について考察した．この分子は通常の状態では閉殻系化合物であったが，コロールの内部空孔にガリウムイオンを加え，分子骨格を湾曲させることでジラジカル性が発現することを明らかにした．これは分子の湾曲により開殻性が発現した珍しい例である．Corrole is a conjugated macrocyclic molecule consisting of four pyrrole units and three methine car-bons, which has been recognized as one of the most important ring-contracted porphyrinoids. The two corrole units can be fused to form different types of tape-like fused corrole dimers. The electronic and magnetic properties can be modulated in response to the fusion mode as well as redox interconver-sion. Recently, we have developed a new motif of tape-like corrole dimer, namely, a triply-linked corrole dimer. While the triply-linked corrole dimer has proved to be a closed-shell molecule in nature, a hiden diradical character has appeared upon molecular distortion caused by gallium complexation. This is a rare example of molecular distortion-induced radical character.