Abstract Both viologen and catechol have been studied extensively. However, the stability of catechol-Fe(III) without additional oxidant is still not well understood. In this paper, we introduced acetocatechol into viologen to investigate its interactions with anion, cation, and reductant, as well as the stability of its Fe(III) complexes. This acetocatechol functionalized viologen, 1,1′-bis(2-(3,4-dihydroxyphenyl)-2-oxoethyl)- [4,4′-bipyridine]-1,1′-diium chloride (H 6 V·Cl 2 ) exists in central symmetric ketone cation form in solid state. Viologen cation increased the acidity of the aceto group and deprotonated the enolic proton to form monodeprotonated enolic H 5 V + in the presence of anion/base, which had the deepest color in organic solvents. The absorbance maximum of H 5 V + increased with the decrease of solvent polarity. It also interacted with B 4 O 7 2− and MoO 4 2− by forming catechol ester in DMSO solution. The catechol moiety can coordinate to metal ion, especially Fe(III), in both aqueous and DMSO solution. In particular, it coordinated to Fe(III) much more readily in aqueous solution than in DMSO. Green monocatecholato Fe(III) and red-brown bis-catecholato Fe(III) complex also formed in aqueous solution. The monocatecholato Fe(III) complex first-order dimerized in aqueous solution at room temperature but underwent second-order decomposition to Fe(II) complex at 60 °C. The biscatecholato Fe(III) complex also transferred to other Fe(III) complexes at first- and second-order at room-temperature and 60 °C respectively. The t 1/2 varied from several hours at room-temperature and several minutes at 60 °C at 10 −4 M concentration. The interactions of Fe(III) in DMSO is much more complex than that of acetocatecholate without viologen. Fe(III) can also be reduced to free viologen radicals in the presence of sodium Na 2 S 2 O 4 , but not N 2 H 4 . In conclusion, this polyfunctional compound responds to anion via aceto and catechol, metal ion via catechol hydroxyl, while reductant via viologen.

中文翻译：

---

乙酰儿茶酚官能化紫精作为多功能材料，在水性和有机溶剂中响应阴离子、阳离子和还原剂

摘要 紫精和儿茶酚都得到了广泛的研究。然而，儿茶酚-Fe(III) 在没有额外氧化剂的情况下的稳定性仍不清楚。在本文中，我们将乙酰儿茶酚引入紫精中，以研究其与阴离子、阳离子和还原剂的相互作用，以及其 Fe(III) 配合物的稳定性。这种乙酰儿茶酚官能化紫精，1,1'-双(2-(3,4-二羟基苯基)-2-氧乙基)-[4,4'-联吡啶]-1,1'-氯化二鎓(H 6 V·Cl 2 ) 以固态中心对称酮阳离子形式存在。Viologen 阳离子增加了乙酰基的酸度，并在阴离子/碱存在下使烯醇质子去质子化，形成单去质子化的烯醇 H 5 V +，在有机溶剂中颜色最深。H 5 V + 的吸光度最大值随着溶剂极性的降低而增加。它还通过在 DMSO 溶液中形成儿茶酚酯与 B 4 O 7 2- 和 MoO 4 2- 相互作用。儿茶酚部分可以与金属离子配位，尤其是在水溶液和 DMSO 溶液中的 Fe(III)。特别是，它在水溶液中比在 DMSO 中更容易与 Fe(III) 配位。绿色的单儿茶酚铁 (III) 和红棕色的双儿茶酚铁 (III) 络合物也在水溶液中形成。单儿茶酚 Fe(III) 配合物在室温下在水溶液中一级二聚，但在 60°C 下二级分解为 Fe(II) 配合物。双儿茶酚 Fe(III) 配合物也分别在室温和 60°C 下以一级和二级转移到其他 Fe(III) 配合物。t 1/2 从室温下的数小时到60℃下10 -4 M 浓度下的数分钟不等。Fe(III) 在 DMSO 中的相互作用比不含紫精的乙酰儿茶酚酸盐的相互作用复杂得多。Fe(III) 也可以在钠 Na 2 S 2 O 4 存在下还原为紫精自由基，但不能在 N 2 H 4 存在下。总之，这种多功能化合物通过乙酰和邻苯二酚对阴离子，通过邻苯二酚羟基对金属离子作出反应，而通过紫精对还原剂作出反应。