Wang Gang, Shang Congdi, Wang Li, Peng Haonan, Yin Shiwei, Fang Yu
Key Laboratory of Applied Surface and Colloid Chemistry (Ministry of Education), School of Chemistry and Chemical Engineering, Shaanxi Normal University , Xi'an 710062, P. R. China.
J Phys Chem B. 2016 Nov 23;120(46):11961-11969. doi: 10.1021/acs.jpcb.6b08684. Epub 2016 Nov 15.
A pyrenyl unit (Py) was chemically connected to a perylene bisimide (PBI) moiety through a long and flexible linker, 4,7,10-trioxa-1,13-tridecanediamine (TOA), resulting in a fluorescent dyad, PBI-TOA-Py. Ultraviolet-visible absorption and fluorescence studies revealed that the two fluorescent units of PBI-TOA-Py behave independently. However, efficient Förster resonance energy transfer (FRET) from the Py unit to the PBI moiety in solution state was also observed. Temperature and solvent effect studies demonstrated that the energy transfer efficiency is highly dependent upon solution temperature and solvent nature. Specifically, for the dimethylformamide (DMF) solution of PBI-TOA-Py, the FRET efficiency is close to 88% at temperatures below ∼40 °C, but the efficiency greatly decreases to nearly zero when the temperature exceeds ∼80 °C. Moreover, addition of HAc into the DMF solution at room temperature could reduce the energy transfer efficiency to nearly zero, suggesting that the excited state energy of Py cannot be directly transferred to the PBI structure even though they are properly and chemically bonded. On the basis of the observations and time-resolved studies, it is believed that the observed efficient FRET from the Py unit to the PBI moiety occurs mainly through Py excimer formation, which could be a result of intermolecular association of the compound. Thus, the applications of the fluorescent dyad in solvent discrimination and trace water determination in organic solvents were verified through example studies.
一个芘基单元（Py）通过一个长且灵活的连接体4,7,10 - 三氧杂 - 1,13 - 十三烷二胺（TOA）与苝二酰亚胺（PBI）部分化学连接，得到一种荧光二元体PBI - TOA - Py。紫外 - 可见吸收和荧光研究表明，PBI - TOA - Py的两个荧光单元表现独立。然而，在溶液状态下也观察到了从Py单元到PBI部分的高效Förster共振能量转移（FRET）。温度和溶剂效应研究表明，能量转移效率高度依赖于溶液温度和溶剂性质。具体而言，对于PBI - TOA - Py的二甲基甲酰胺（DMF）溶液，在温度低于约40 °C时，FRET效率接近88%，但当温度超过约80 °C时，效率大幅下降至几乎为零。此外，在室温下向DMF溶液中加入HAc可使能量转移效率降低至几乎为零，这表明即使Py和PBI结构通过化学键正确连接，Py的激发态能量也不能直接转移到PBI结构上。基于这些观察结果和时间分辨研究，认为观察到的从Py单元到PBI部分的高效FRET主要通过Py准分子的形成发生，这可能是该化合物分子间缔合的结果。因此，通过实例研究验证了该荧光二元体在有机溶剂中溶剂鉴别和痕量水测定方面的应用。
