Time-resolved laser spectroscopy of nonreactive processes in ionic liquids and their binary mixtures with organic solvents and CO2
Time-resolved laser spectroscopy of nonreactive processes in ionic liquids and their binary mixtures with organic solvents and CO2
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DOI：
10.1016/j.molliq.2013.08.010
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发表时间：
2014-04
影响因子：
6
通讯作者：
N. Ernsting;T. Lenzer;K. Oum
中科院分区：
文献类型：
--
作者：
N. Ernsting;T. Lenzer;K. Oum
非反应动力学的分子在离子液体（ILs）已被研究在各种环境中，如在纯质子和质子的ILs，以及在二元混合物的ILs与极性有机溶剂和CO2。从飞秒到毫秒的时间尺度上的瞬态宽带吸收和荧光光谱技术已被应用于阐明这些介质中不同类型的溶质-溶剂相互作用的重要性。分子探针如12′-apo-β-胡萝卜素-12 ′-酸和香豆素C153已被用作离子液体溶剂化动力学、微极性、氢键和碰撞弛豫的报告分子。以香豆素C153为溶剂，定量研究了溶剂化响应与纯液微波太赫兹吸收测量之间的关系。电导率的降低值在此类溶剂化实验中起着关键作用。非质子离子液体表现出比其静态介电常数预期的更大的微极性，而质子烷基甲酸铵离子液体的局部极性似乎与具有相当介电常数的醇的极性相似。在IL与有机溶剂或CO2的混合物中，没有迹象表明分子探针周围的本体组成和局部组成存在差异。离子液体中的碰撞弛豫过程发生在与偶极有机溶剂中相似的时间尺度上。
Nonreactive dynamics of molecules in ionic liquids (ILs) have been investigated in various environments, such as in neat aprotic and protic ILs, as well as in binary mixtures of ILs with polar organic solvents and CO2. Transient broadband absorption and fluorescence spectroscopic techniques on timescales from femtoseconds to milliseconds have been applied to elucidate the importance of different types of solute–solvent interactions in these media. Molecular probes such a 12′-apo-β-carotenoic-12′-acid and Coumarin C153 have been used as reporter molecules for ionic liquid solvation dynamics, micropolarity, hydrogen-bonding and collisional relaxation. With Coumarin C153 in ILs, the relationship between the complete solvation response and microwave-terahertz absorption measurements of the neat liquid was explored quantitatively. A reduced value for the conductivity plays a key role in such solvation experiments. Aprotic ILs exhibit a micropolarity larger than expected from their static dielectric constants, whereas the local polarity of protic alkylammonium formate ILs appears to be similar to that of alcohols having comparable dielectric constants. In IL mixtures with organic solvents or CO2, there is no indication for differences in the bulk composition and the local composition around the molecular probe. Collisional relaxation processes in ILs take place on similar timescales as in dipolar organic solvents.