多環芳香族炭化水素 (PAH)は一般にp型半導体の性質を持ち, 置換基導入によって自己組織的な集積構造の形成が可能である。このようなPAH誘導体にヘテロユニットを導入すると光および電子物性の制御が期待できる。そこで本研究では, 代表的なPAHであるトリフェニレン を基盤として基本骨格にヘテロ原子や置換基の導入を行い, 電気化学特性や励起ダイナミクスの制御に成功した。特に, TPh骨格に窒素原子およびトリイミドを縮環させたヘキサアザトリフェニレントリイミド (HAT-TIm)は優れたn型特性を示した。さらに, HAT-TImとポルフィリンと組み合わせた超分子型光エネルギー変換系(CT錯体)へ展開した。
Charge-transfer (CT) π-complexes are formed between planar porphyrins and 1, 4, 5, 8, 9, 12-hexaazatriphenylene (HAT) derivatives with large formation constants, exhibiting broad CT absorption bands. The unusually large formation constants result from close face-to-face contact between two planar π-planes of porphyrins and HAT derivatives. The redox potentials of porphyrins and HAT derivatives measured by cyclic voltammetry indicate that porphyrins and HAT derivatives act as electron donors and acceptors, respectively. Formation of 1 : 1 CT complexes between porphyrins and HAT derivatives was examined by the UV-vis, fluorescence and 1H NMR measurements in nonpolar solvents. The occurrence of unprecedented ultrafast photoinduced electron transfer from the porphyrin unit to the HAT unit in the CT π-complex was observed by femtosecond laser flash photolysis measurements. Highly linear aggregate composed of a planar porphyrin and an HAT derivative was observed by TEM and AFM.
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