Water-Soluble Phospholo[3,2-b]phosphole P,P’-Dioxide-Based Fluorescent Dyes with High Photostability
Chenguang Wang, Aiko Fukazawa, Yoshiyuki Tanabe, Naoto Inai, Daisuke Yokogawa, Shigehiro Yamaguchi, Chem. Asian J., Early View.
[DOI: 10.1002/asia.201800533]
我々は最近,架橋構造により平面固定化したベンゾ[b]ホスホール-P-オキシド誘導体が既存の蛍光色素と比較して圧倒的に高い耐光性をもつことを見出し,従来の色素では実現困難なSTED顕微鏡での繰り返し撮像 (Angew. Chem. Int. Ed. 2015, 54, 15213) や Z-scan STEDイメージング (J. Am. Chem. Soc. 2017, 139, 10374) が可能となることを明らかにしている. この「超耐光性」とも呼べる並外れた耐光性を実現するための分子設計指針についてさらなる知見を得るとともに,発光特性や物理的性質のさらなるチューニングを行うことを目的とし,本研究では架橋部位にホスホリル基 ([P=O]R) をもつベンゾホスホールオキシドを合成し,架橋部位が光学特性や耐光性に及ぼす効果について検討した.その結果,ホスホリル架橋ベンゾホスホールオキシドは他の架橋部位をもつ誘導体よりも長波長側に吸収および蛍光を示すことに加え,大きなストークスシフトを示すことを明らかにした.また,架橋部位の幾何異性が耐光性に影響を及ぼし,P=O の向きが同じの cis 体よりも trans体の方が圧倒的に高い耐光性をもつことを見出した.以上の結果は,超耐光性蛍光色素の分子設計に重要な指針を与えるものであるといえる.
We have recently reported the fluorescent dye PB430, which consists of a 2-phenyl-substituted benzophosphole P-oxide skeleton that is reinforced with a methylene bridge. PB430 showed pronounced photostability and thus high utility for applications in super-resolution stimulated emission depletion (STED) microscopy. In the present study, we replaced the methylene bridge with another P=O group to (i) investigate the role of the bridging moieties, and (ii) further modulate the fluorescence properties. We synthesized a series of phospholo[3,2-b]phosphole-based dyes, i.e., trans-PO-PB430, cis-PO-PB430, and trans-PO-PB460, all of which show sufficient water solubility. Moreover, trans-PO-PB430 and trans-PO-PB460 exhibit intense green and orange fluorescence, respectively, and a high photostability that is comparable to that of PB430. In contrast, cis-PO-PB430 underwent rapid photobleaching upon continuous photoirradiation, which demonstrates the importance of steric shielding of the polycyclic skeleton with the substituents on the bridging moieties. The fluorescence properties of these dyes were insensitive to concentration, pH value, and polarity changes of the environment in solution. In addition, even in the solid state, these dyes show strong green to orange emissions. These results demonstrate the potential utility of trans-PO-PB430 and trans-PO-PB460 as highly photostable fluorescent dyes.
ホスホリル架橋ベンゾホスホールオキシド:水溶性の高い超耐光性蛍光色素の分子設計
2018/05/01