SOLVENT EFFECTS ON EMISSION YIELD AND LIFETIME FOR COUMARIN LASER-DYES - REQUIREMENTS FOR A ROTATORY DECAY MECHANISM
SOLVENT EFFECTS ON EMISSION YIELD AND LIFETIME FOR COUMARIN LASER-DYES - REQUIREMENTS FOR A ROTATORY DECAY MECHANISM
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DOI：
10.1021/j100248a024
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发表时间：
1985-01-01
影响因子：
--
通讯作者：
BERGMARK, WR
中科院分区：
文献类型：
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作者：
JONES, G;JACKSON, WR;BERGMARK, WR
测定了香豆素类激光染料在各种有机溶剂、水和混合介质中的光物理参数。荧光发射产率和寿命对溶剂极性变化的响应是香豆素取代模式的敏感函数。最重要的是取代基的影响，导致在较大的激发态偶极矩（荧光状态），在7位的胺基的旋转运动的限制，和离域的激发能远离香豆素部分。对于染料显示急剧减少的排放量和寿命增加溶剂极性，质子mediaand特别是水是最有效的ininininhibiting荧光虽然氘同位素效应（H20/D20）的物理参数是最小的。测量了两种溶剂敏感染料在乙腈和高粘度溶剂甘油中的发射产额和寿命的温度依赖性。对于寿命> 2 ns的染料，还观察到氧气对香豆素荧光的猝灭。本文讨论了香豆素染料的主要物理化学特征，包括分子内电荷转移（ICT）激发态的发射和一个重要的非辐射衰减路径，该路径涉及胺官能团（7位）的旋转，导致扭曲的分子内CT态（TICT）。这种先前提出的非辐射衰减路径是香豆素结构，溶剂极性和粘度，和温度的一个微妙的functionof，是最敏感的取代基模式，本地化的激发在7-氨基和稳定的电荷在扭曲的两性离子（TICT）中间体。涉及旋转基团的激发态键级在确定ICT-1型相互转化重要性中的作用
Photophysical parameters have been determined for coumarin laser dyes in a variety of organic solvents and in water and mixed media. The response of fluorescence emission yield and lifetime to changes in solvent polarity was a sensitive function of coumarin substitution pattern. Most important were substituent influences which resulted in larger excited-state dipole moments (for the fluorescent state), in restrictions of rotatory motion for the amine group at the 7-position, and the delocalization of excitation energy away from the coumarin moiety. For dyes displaying sharp reductions in emission yield and lifetime with increased solvent polarity, protic mediaand particularly water were most effective ininhibiting fluorescence although deuterium isotope effects (H20/D20) on photophysical parameters were minimal. The temperature dependence of emission yield and lifetime was measured for two solvent-sensitive dyes in acetonitrile and in a highly viscous solvent, glycerol. The quenching of coumarin fluorescence by oxygen for dyes with lifetimes> 2 ns was also observed. The dominant photophysical features for coumarin dyes are discussed in terms of emission from an intramolecular charge-transfer (ICT) excited state and an important nonradiative decay path involvingrotation of the amine functionality (7-position) leadingto a twisted intramolecular CT state (TICT). This previously proposed nonradiative decay path is a subtle functionof coumarin structure, solvent polarity and viscosity, and temperature and is most sensitive to substituent patterns which localize excitation at the 7-amino group and which stabilize charge in the twisted zwitterionic (TICT) intermediate. The role of excited-state bond orders involving the rotating group in determining the importance of interconversions of the type ICT-»