Department of Chemistry, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.
Methods Appl Fluoresc. 2016 May 4;4(2):024004. doi: 10.1088/2050-6120/4/2/024004.
The excited-state proton transfer (ESPT) of the strong photoacid, N-methyl-7-hydroxyquinolinium, was studied in the presence of different weak bases such as methanol, ethanol, and dimethyl sulfoxide in an aprotic solvent of acetonitrile. Here, we present chemical kinetics analysis of the ESPT mechanism to explain biphasic fluorescence decay of the parent photoacid and the sign reversal of the rise and decay of the resulting conjugate-base fluorescence. The ESPT of the free photoacid showed a molecularity of 2 with reacting alcohol molecules. In the ground state, it was found that a fraction of the photoacid formed 1 : 2 hydrogen-bonded complexes with the residual water present in the aprotic solvent or 1 : 1 complexes with the additive alcohols. In the excited state, these adducts underwent proton transfer when complexed further with diffusing alcohol molecules.
强质子酸 N-甲基-7-羟基喹啉鎓在无质子溶剂乙腈中，于不同弱碱甲醇、乙醇和二甲亚砜存在的条件下，其激发态质子转移（ESPT）被研究。在这里，我们提出了 ESPT 机制的化学动力学分析，以解释母体光酸的双相荧光衰减和生成的共轭碱荧光的上升和衰减的符号反转。游离光酸的 ESPT 表现出与反应醇分子的 2 分子性。在基态时，发现一部分光酸与非质子溶剂中存在的残留水分子形成 1:2 氢键复合物，或与添加剂醇形成 1:1 复合物。在激发态时，这些加合物与扩散的醇分子进一步络合时会发生质子转移。
