School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Drive, Atlanta, GA 30332, USA.
Chemistry. 2009 Dec 7;15(47):13075-81. doi: 10.1002/chem.200900608.
We have investigated the UV/Vis absorption and emission of 1,4-bis(4'-dibutylaminostyryl)benzene (1) upon protonation with trifluoroacetic acid in dichloromethane and in acetonitrile. We find that 1 does not display significantly dynamic acidity in the excited state, that is, it is not a photoacid. Three protonation states of 1 were investigated, all of which, neutral, singly protonated, and bis-protonated, are fluorescent. As an isolable model for the mono-protonated species, a methylated derivative of 1 was prepared by reaction with methyl triflate. This species displays redshifted emission but similar absorption as the non-quaternized parent, 1. The strong observed emission of all three protonated states of 1 suggests that the kinetic photoacidity of 1* is low or absent. We assume that the lifetime of the excited state is too short to allow solvent reorganization and therefore we cannot make a statement on the thermodynamic photoacidity of the protonated forms of 1.
我们研究了 1,4-双(4'-二丁氨基苯乙烯基)苯（1）在二氯甲烷和乙腈中用三氟乙酸质子化时的紫外/可见吸收和发射。我们发现 1 在激发态下没有明显的动态酸度，也就是说，它不是光酸。我们研究了 1 的三种质子化状态，中性、单质子化和双质子化状态都是荧光的。作为单质子化物种的可分离模型，通过与甲基三氟甲磺酸酯反应制备了 1 的甲基化衍生物。该物质显示出红移的发射，但与未季铵化的母体 1 的吸收相似。1 的所有三种质子化状态的强观察到的发射表明 1*的动力学光酸度较低或不存在。我们假设激发态的寿命太短，无法允许溶剂重组，因此我们无法对 1 的质子化形式的热力学光酸度做出陈述。
