Sebok-Nagy Krisztina, Miskolczy Zsombor, Biczók László
Chemical Research Center, Hungarian Academy of Sciences, Budapest, Hungary.
Photochem Photobiol. 2005 Sep-Oct;81(5):1212-8. doi: 10.1562/2005-01-14-RA-415.
The fluorescent properties of 2-hydroxy Nile red dye (HONR) proved to be highly sensitive to the basicity of hydrogen bond acceptors. Fluorescence quantum yields and fluorescence decay profiles were measured as the function of the concentration of organic nitrogen compounds in solvents of various polarities. The detailed mechanism and the kinetics of the fluorescence quenching were revealed with the combined analysis of the steady-state and time-resolved spectroscopic data. The relative contribution of the competing reaction steps was found to be very sensitive to the basicity of the additive and to solvent polarity. The most profound change appeared in the unimolecular deactivation pathways of the excited hydrogen-bonded HONR, whereas the formation rate of this species varied to a lesser extent. The dissociation into excited HONR and ground-state base was able to compete with the energy dissipation only when 2,4,6-trimethylpyridine was used as hydrogen bond acceptor in toluene. The bimolecular quenching of the excited hydrogen-bonded complex played significant role in apolar solvents. Proton displacement along the hydrogen bond in the excited complex led to excited ion pairs in polar media.
2-羟基尼罗红染料（HONR）的荧光特性被证明对氢键受体的碱性高度敏感。荧光量子产率和荧光衰减曲线作为各种极性溶剂中有机氮化合物浓度的函数进行了测量。通过稳态和时间分辨光谱数据的联合分析揭示了荧光猝灭的详细机制和动力学。发现竞争反应步骤的相对贡献对添加剂的碱性和溶剂极性非常敏感。最显著的变化出现在激发态氢键结合的HONR的单分子失活途径中，而该物种的形成速率变化较小。仅当在甲苯中使用2,4,6-三甲基吡啶作为氢键受体时，分解为激发态HONR和基态碱才能与能量耗散竞争。激发态氢键结合复合物的双分子猝灭在非极性溶剂中起重要作用。激发复合物中质子沿氢键的位移导致极性介质中形成激发离子对。
