Dynamics in Organic Ionic Liquids in Distinct Regions Using Charged and Uncharged Orientational Relaxation Probes
Dynamics in Organic Ionic Liquids in Distinct Regions Using Charged and Uncharged Orientational Relaxation Probes
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DOI：
10.1021/jp911123v
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发表时间：
2010-03-04
影响因子：
3.3
通讯作者：
Fayer, M. D.
中科院分区：
文献类型：
--
作者：
Fruchey, Kendall;Fayer, M. D.
在1-烷基-3-甲基咪唑双（三氟甲磺酰基）亚胺（烷基=乙基、丁基、己基、辛基）有机室温离子液体（RTIL）中，测定了苝和8-甲氧基芘-1,3,6-磺酸钠（MPTS）的温度依赖性荧光各向异性衰减（取向弛豫）。当使用Stokes-Einstein-Debye理论分析时，两种荧光探针分子显示出明显不同的旋转动力学，表明它们位于RTILs内不同的环境中，并且与周围环境具有非常不同的相互作用。苝具有顺滑性旋转，随着离子液体烷基链长度的增加，顺滑性越来越强。动力学近似于有机油中苝的动力学。相比之下，MPTS表现出超粘行为，可能反映了与RTIL阳离子的非常强的协调性。这些结果与离子液体结构中旋转摩擦的不同元素一致，这些元素可用于溶质，取决于它们的化学功能。
The temperature-dependent fluorescence anisotropy decay (orientational relaxation) of perylene and sodium 8-methoxypyrene-1,3,6-sulfonate (MPTS) were measured in a series of 1-alkyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (alkyl = ethyl, butyl, hexyl, octyl) organic room temperature ionic liquids (RTIL). The two fluorescent probe molecules display markedly different rotational dynamics when analyzed using Stokes-Einstein-Debye theory, demonstrating that they are located in distinct environments within the RTILs and have very different interactions with their surroundings. Perylene rotates with subslip behavior, becoming increasingly subslip as the length of ionic liquid alkyl chain is increased. The dynamics approach those of perylene in an organic oil. In contrast, MPTS shows superstick behavior, likely reflecting very strong coordination with the RTIL cations. These results are consistent with different elements of rotational friction within the ionic liquid structure, which are available to solutes depending on their chemical functionality.