A red-emissive aminobenzopyrano-xanthene dye: elucidation of fluorescence emission mechanisms in solution and in the aggregate state
作者:Shinichiro Kamino、Atsuya Muranaka、Miho Murakami、Asana Tatsumi、Noriyuki Nagaoka、Yoshinao Shirasaki、Keiko Watanabe、Kengo Yoshida、Jun Horigome、Seiji Komeda、Masanobu Uchiyama、Shuichi Enomoto
DOI:10.1039/c2cp43503a
日期:——
We have designed and synthesized a new class of rhodamine dyes with an extended π-conjugated system and named them 3′,3′′-bis(oxospiroisobenzofuran)-3,7-bis(diethylamino)benzopyrano-xanthene (ABPX01) dyes. ABPX01 exhibits fluorescence emission in both dilute solution and the aggregate state, whereas conventional rhodamine dyes show aggregation-induced quenching (AIQ). The chemical species of ABPX01 in solution were determined by spectrophotometric measurements and density functional theory (DFT) calculations to study the relationship among chemical species, color, and fluorescence emission. ABPX01 has various forms: the spirolactone form (ABPX010), which is colorless; and the monocationic form (ABPX01H+) and the dicationic form (ABPX01H22+), which are colored. By orienting a pair of spirolactone benzene moieties differently, the stereoisomers of trans- and cis-ABPX010 were separated and their crystal structures determined. ABPX01H22+ was identified to be a red fluorescent species. Detailed spectroscopic and electron microscopic investigations led to the assumption that the ABPX01H22+ formed ion associates with Cl− as counter anions in HCl aqueous solution, and the nano- and submicrometer-sized colloidal aggregates of ABPX01 hydrochloride exhibit fluorescence emission. To further verify the aggregation-induced emission enhancement (AIEE) mechanism, ABPX01 hydrochloride was synthesized and its fluorescence was similarly checked in the powder state. AIEE in ABPX01 might be attributed to the synergistic combination of the restriction of dye–dye interaction induced dimer formation by sterically hindered ion associates and carboxylic benzene moieties, and the structural rigidity and intermolecular arrangement of the xanthene moiety. We expect that the design strategy of ABPX dyes will be extended to the development of a wide variety of functional organic-dye-based fluorophores (ODFs) with suitable fluorescence-emission controlled mechanisms for many useful applications in new electroluminescent devices.
我们设计并合成了一类具有扩展π共轭体系的新型罗丹明染料,并将其命名为 3′,3′′-双(氧代异苯并呋喃)-3,7-双(二乙基氨基)苯并吡喃-氧杂蒽染料(ABPX01)。ABPX01 在稀溶液和聚集状态下都能发出荧光,而传统的罗丹明染料则会出现聚集诱导淬灭(AIQ)。通过分光光度测量和密度泛函理论(DFT)计算,确定了 ABPX01 在溶液中的化学种类,从而研究了化学种类、颜色和荧光发射之间的关系。ABPX01 有多种形态:螺内酯形态(ABPX010)是无色的;单内酯形态(ABPX01H+)和双内酯形态(ABPX01H22+)是有色的。通过改变一对螺内酯苯分子的方向,反式和顺式 ABPX010 的立体异构体被分离出来,并确定了它们的晶体结构。经鉴定,ABPX01H22+ 是一种红色荧光物种。通过详细的光谱和电子显微镜研究,可以推测 ABPX01H22+ 形成的离子在盐酸水溶液中与作为反阴离子的 Cl- 结合,ABPX01 盐酸盐的纳米级和亚微米级胶体聚集体呈现荧光发射。为了进一步验证聚集诱导发射增强(AIEE)机制,我们合成了 ABPX01 盐酸盐,并同样检测了其在粉末状态下的荧光。ABPX01 中的 AIEE 可能归因于立体受阻离子缔合物和羧基苯分子对染料-染料相互作用诱导的二聚体形成的限制,以及呫吨分子的结构刚性和分子间排列的协同作用。我们希望 ABPX 染料的设计策略能够扩展到开发各种功能性有机染料荧光团(ODF),这些荧光团具有合适的荧光发射控制机制,可用于新型电致发光器件中的许多有用应用。