Dynamic Stokes Shift of 9,9′-Bianthryl in Ionic Liquids: A Temperature Dependence Study†
Dynamic Stokes Shift of 9,9′-Bianthryl in Ionic Liquids: A Temperature Dependence Study†
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离子液体中 9,9′-联蒽的动态斯托克斯位移：温度依赖性研究†
DOI：
10.1021/jp9020454
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发表时间：
2009
影响因子：
3.7
通讯作者：
H. Miyasaka
中科院分区：
文献类型：
--
作者：
Y. Nagasawa;Akito Oishi;Tsuyoshi Itoh;Masakazu Yasuda;Masayasu Muramatsu;Y. Ishibashi;S. Ito;H. Miyasaka
采用稳态和时间分辨检测方法研究了9，9 ′-联蒽（BA）在咪唑类离子液体（IL）中电荷转移（CT）态的荧光行为与温度的关系.在室温和较高温度下，离子液体中BA的发射峰随着温度的降低而向较长波长移动，这是在正常极性溶剂中常见的现象。另一方面，发射峰随着温度的降低而向短波长移动。29万进行时间分辨荧光（TRF）光谱以研究动态斯托克斯位移，即，荧光峰的时间依赖性红移。在高粘性离子液体中，动态斯托克斯位移的时间常数变得与CT状态的寿命相当或更长。在这种情况下，BA的基态在溶剂化过程完成之前恢复。结论是低温蓝移发光的起源是由于低温下的光吸收引起的。
The temperature dependence of the fluorescence behaviors of 9,9′-bianthryl (BA) in the charge-transferred (CT) state in imidazolium ionic liquids (IL) was investigated by means of steady-state as well as time-resolved detections. At ambient and higher temperatures, the emission peak of BA in ILs shifted to longer wavelengths with decreasing temperature, which is a phenomenon commonly observed in normal polar solvents. On the other hand, the emission peak shifted toward shorter wavelengths with decreasing temperature below ca. 290 K. Time-resolved fluorescence (TRF) spectroscopy was carried out to investigate the dynamic Stokes shift, i.e., the time-dependent red-shift of the fluorescence peak. In highly viscous ILs, the time constant of the dynamic Stokes shift becomes comparable or longer than the lifetime of the CT state. In such a case, the ground state of BA is recovered before the completion of the solvation process. It is concluded that the origin of the blue-shifted emission at lower temperatures i...