School of Chemistry, Seoul National University, NS60, Seoul 151-747, Korea.
J Phys Chem A. 2010 Nov 4;114(43):11432-5. doi: 10.1021/jp106301q.
The excited-state double proton transfer of model DNA base pairs, 7-hydroxyquinoline dimers, in benzene has been investigated using picosecond time-resolved fluorescence spectroscopy. Upon excitation, whereas singly hydrogen-bonded noncyclic dimers do not go through tautomerization within the relaxation time of 1400 ps, doubly hydrogen-bonded cyclic dimers undergo excited-state double proton transfer on the time scale of 25 ps to form tautomeric dimers, which subsequently undergo a conformational change in 180 ps to produce singly hydrogen-bonded tautomers. The rate constant of the double proton transfer reaction is temperature-independent, showing a large kinetic isotope effect of 5.2, suggesting that the rate is governed mostly by tunneling.
采用皮秒时间分辨荧光光谱法研究了模型 DNA 碱基对、7-羟基喹啉二聚体在苯中的激发态双质子转移。激发时，虽然单氢键非环二聚体在 1400 ps 的弛豫时间内不会经历互变异构，但双氢键环二聚体在 25 ps 的时间尺度上经历激发态双质子转移，形成互变异构二聚体，随后在 180 ps 内发生构象变化，生成单氢键互变异构体。双质子转移反应的速率常数与温度无关，表现出 5.2 的大动力学同位素效应，表明速率主要由隧道效应控制。
