Klinska Marta, Smith Leesa M, Gryn'ova Ganna, Banwell Martin G, Coote Michelle L
Research School of Chemistry , Australian National University , Canberra ACT 2601 , Australia . Email:
ARC Centre of Excellence for Electromaterials Science , Australia.
Chem Sci. 2015 Oct 1;6(10):5623-5627. doi: 10.1039/c5sc01307k. Epub 2015 Jun 23.
Time-dependent fluorescence spectroscopy has been used to demonstrate significant pH-dependent electrostatic effects on the kinetics and thermodynamics of hydrogen atom transfer between 1-hydroxy-2,2,6,6-tetramethyl-4-piperidinecarboxylic acid (4-CT-H) and the profluorescent nitroxide {2,2,6,6-tetramethyl-4-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-1-piperidinyl}oxidanyl radical (PFN) in dichloromethane. This pH switching does not occur when 4-CT-H is replaced with a structurally analogous hydroxylamine that lacks an acid-base group, or when the polarity of the solvent is increased. These findings validate our recent theoretical predictions that electrostatic stabilisation of delocalised radicals is of functional significance in low polarity environments.
时间分辨荧光光谱已被用于证明，在二氯甲烷中，1-羟基-2,2,6,6-四甲基-4-哌啶甲酸（4-CT-H）与前荧光氮氧化物{2,2,6,6-四甲基-4-[(7-硝基-2,1,3-苯并恶二唑-4-基)氨基]-1-哌啶基}氧化自由基（PFN）之间的氢原子转移动力学和热力学存在显著的pH依赖性静电效应。当4-CT-H被缺乏酸碱基团的结构类似的羟胺取代时，或者当溶剂极性增加时，这种pH转换不会发生。这些发现证实了我们最近的理论预测，即在低极性环境中，离域自由基的静电稳定具有功能意义。
