機能性有機ホウ素化合物合成ビルディングブロック

ホウ素は空のp軌道を持ち，共役系分子にホウ素を導入することにより，p-pi*相互作用を生かした，優れた機能性分子の設計が可能となります。例えば山口らは，ジメシチルフルオロボランを原料に用い，電子豊富なpi電子系の側鎖に受容性のホウ素置換基を導入した2,5-ビス[4-(N,N-ジフェニルアミノ)フェニルエチニル]ベンゼン誘導体を合成しています。この分子は強い蛍光特性を示し，溶液状態だけでなく，固体状態でも量子収率90%と，優れた数値を示します。

“Highly Emissive Organic Solids Containing 2,5-Diboryl-1,4-phenylene Unit”

C.-H. Zhao, A. Wakamiya, Y. Inukai, S. Yamaguchi, J. Am. Chem. Soc. 2006, 128, 15934. DOI: 10.1021/ja0637550

We disclosed a series of π-conjugated systems containing 2,5-bis(dimesitylboryl)-1,4-phenylene as the core unit and electron-donating amino groups at the terminal positions. The extension of the pπ−π* conjugation in the diborylphenylene moiety along the short axis of the π-conjugated framework as well as the incorporation of two bulky dimesitylboryl groups at the para-positions makes this moiety act as a unique bulky π-electron-accepting unit. As a consequence, these systems behave like donor−acceptor−donor quadrupolar π-electron systems and show a large solvatochromism in the fluorescence spectra. Moreover, these organoboron π systems exhibit intense fluorescence even in the solid state with the quantum yields of 0.73−0.90.