六芳基联咪唑(Hexaarylbiimidazole,HABI)的光致变色效应,是1960年Hayashi和Maeda在研究2,4,5-三苯基咪唑氧化时产生化学发光的过程中偶然发现的。作为一类新型光致变色分子,HABI同时具有光致变色、热致变色以及压致变色特性。其变色机理是光照打断HABI分子中两个咪唑环之间的C—N化学键,产生两分子三苯基咪唑自由基(triphenylimid—azoleradical,TPIR)。由于HABI在变色后形成的有色态(TPIR)褪色比较慢(半衰期τ1/2为几分钟到几十分钟),同时生成的自由基比较活泼,容易发生不可逆副反应,使得其作为光致变色材料的抗疲劳性较差。近十几年,JiroAbe课题组提出桥联绑定两个三苯基咪唑的构想,使得HABI的光致变色逆反应的半衰期由数分钟降低到几十微秒,尤其是近期,改性后的HABI成功运用于实时全息成像,显示了HABI作为新型光致变色材料的美好前景。本课题组在前人研究基础上,将HBAI的光致变色效应发展成荧光分子开关,设计合成出具有荧光分子开关性能的HABI并加以优化,成功地运用于超分辨成像。基于HABI的荧光分子开关及其新兴光学应用有望成为分子开关研究的新热点。
Hexaarylbiimidazole(HABI)was first discovered as photochromic material in 1960 by Hayashi and Maeda when they investigated the chemiluminescence formed by oxidation of 2,4,5-triphenylimidazole. HABI is new photochromism material, which also possess thermochromism and piezochromism. The photochromism mechanism of HABI is the photo-induced homogeneous cleavage of the C--N bond between the two imidazole rings followed by the formation of two triphenylimidazole radical. As the speed of the colored species dimerizes to HABI (colorless species) is very slow (rl/2 is about minutes) and the triphenylimidazole radicals are relatively reactive, the fatigue resistance is very poor. In recent years, Jiro Abe's group proposed an idea of using a "bridge structure" to inhibit the diffusion of TPIRs. In this way the decay half-life of the TPIR reduced from minutes to tens of micro seconds. Lately, they applied modified HABIs in holographic imaging, which exhibits the great potential of HABt as photochromic materials. Meanwhile, designing and synthesizing proper fluorescent HABI photoswitches and their applications to super-resolution microscopy imaging are undertaken in our group.