School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia 30332-0400, USA.
Phys Chem Chem Phys. 2011 Sep 7;13(33):14914-27. doi: 10.1039/c1cp20952c. Epub 2011 Jul 14.
We have studied an excited state proton transfer (ESPT) from the cationic "super" photoacid N-methyl 6-hydroxyquinolinium perfluorobutane sulfonate to non-aqueous solvents using picosecond and nanosecond time-resolved fluorescence spectroscopy. Upon the photoinduced adiabatic deprotonation from the hydroxyl moiety, a quinolinium zwitterion with a highly anisotropic charge distribution is formed. Due to the complexity of the resultant photodissociated system, the typical description of the reversible ESPT within the framework of the Spherically Symmetric Diffusion Problem (SSDP) is not possible. Additional complications are caused by the presence of a counteranion particle which affects the proton mobility. To better understand the ESPT process, we have performed extensive Brownian dynamics (BD) simulations of this three-body system as a tool to reveal the nature of the nonstationary interaction potentials and to elucidate the role of a counterion in the diffusion and reactive properties of the proton. Moreover, our results demonstrated that the anisotropy of the potential force can be taken into account after adapting this force for use in the SSDP. The results of both BD simulations and SSDP calculation with the adapted force field were used to fit the experimental kinetics of this three-body problem adequately.
我们使用皮秒和纳秒时间分辨荧光光谱法研究了从阳离子“超”光酸 N-甲基 6-羟基喹啉翁全氟丁烷磺酸盐到非水溶剂的激发态质子转移（ESPT）。在从羟基部分光诱导绝热去质子化后，形成具有高度各向异性电荷分布的喹啉翁两性离子。由于所得光解离体系的复杂性，不可能在球对称扩散问题（SSDP）的框架内对可逆 ESPT 进行典型描述。存在抗衡离子粒子会影响质子迁移率，这会导致额外的复杂性。为了更好地理解 ESPT 过程，我们对这个三体系统进行了广泛的布朗动力学（BD）模拟，作为揭示非稳态相互作用势性质的工具，并阐明抗衡离子在质子扩散和反应性质中的作用。此外，我们的结果表明，在将该力适应于 SSDP 后，可以考虑势力的各向异性。BD 模拟和 SSDP 计算的结果与适应力场一起用于适当地拟合这个三体问题的实验动力学。
