Development of pH-Sensitive Spin-Crossover Complex Film and Direct Observation of Proton Flow

在高质子导电性的Nafion膜[FeII(diAMsar)]@Nafion （diAMsar = 1,8-diaminosarcophagine）中，ph敏感的自旋交叉铁（II）配合物的自旋态被施加电压引起的电场诱导质子浓度梯度时空操纵。[Fe(II)(diAMsar)]在酸性条件下具有Fe（II）的高自旋（HS）态，而在碱性条件下具有低自旋（LS）态，这是由于diAMsar末端氨基的质子化/去质子化与颜色变化有关。施加电压可逆地诱导了[Fe(II)(diAMsar)]@Nafion的时变颜色变化，对应于[Fe(II)(diAMsar)]的动态自旋交叉行为。通过这种方法，我们首次使用ph敏感自旋交叉配合物作为颜色指示器来可视化Nafion膜中的质子流动。

The spin state of a pH-sensitive spin-crossover iron(II) complex in highly proton-conductive Nafion membrane, [FeII(diAMsar)]@Nafion (diAMsar = 1,8-diaminosarcophagine), was spatiotemporally manipulated by electric field-induced proton concentration gradient derived from applied voltage. [Fe(II)(diAMsar)] has the high-spin (HS) state of Fe(II) in acidic condition, whereas it has the low-spin (LS) state in basic condition due to the protonation/deprotonation of the terminal amino groups of diAMsar being associated with color change. Applied voltage reversibly induced the time-variable color change of [Fe(II)(diAMsar)]@Nafion, corresponding to the dynamical spin-crossover behavior of [Fe(II)(diAMsar)]. In this way, we visualized the proton flow in Nafion membrane by using the pH-sensitive spin-crossover complex as a color indicator for the first time.