Ferrocene clicked polypyrrole derivatives: effect of spacer group on electrochemical properties and post-polymerization functionalization

In this study, novel ferrocene-functionalized N-alkyl substituted pyrrole derivatives, namely 4-ferrocenyl-1-[3-(pyrrol-1-yl)propyl]-1H-1,2,3-triazole (Py3Fc), 4-ferrocenyl-1-[4-(pyrrol-1-yl)butyl]-1H-1,2,3-triazole (Py4Fc), and 4-ferrocenyl-1-[6-(pyrrol-1-yl)hexyl]-1H-1,2,3-triazole (Py6Fc), were synthesized via click reaction and the monomers were characterized by 1H NMR, 13C NMR, FTIR, and HRMS techniques. Redox properties of the monomers were investigated by cyclic voltammetry (CV) studies. Contrary to general literature, both Py4Fc and Py6Fc were electrochemically polymerized without loss in redox activity of ferrocene group. Moreover, click chemistry was utilized in post-polymerization functionalization. For this purpose, three azide-containing polypyrroles, P(Py3N3), P(Py4N3), and P(Py6N3) were electrochemically synthesized and subjected to click reaction in the presence of ethynylferrocene. CV studies of the post-polymerization functionalized polymers revealed quasi-reversible waves, while only P(Py6-post-Fc) showed the characteristic redox behavior of both polypyrrole and ferrocene. Thus, in this study preparation of a conducting homopolymers of pyrrole having covalently bonded ferrocene units was demonstrated and effect of spacer group is investigated.

本研究通过点击化学反应合成了新型二茂铁功能化N-烷基取代吡咯衍生物，即4-二茂铁基-1-[3-(吡咯-1-基)丙基]-1H-1,2,3-三唑（Py3Fc）、4-二茂铁基-1-[4-(吡咯-1-基)丁基]-1H-1,2,3-三唑（Py4Fc）以及4-二茂铁基-1-[6-(吡咯-1-基)己基]-1H-1,2,3-三唑（Py6Fc）；随后采用氢核磁共振谱（1H NMR）、碳核磁共振谱（13C NMR）、傅里叶变换红外光谱（FTIR）与高分辨质谱（HRMS）对所得单体进行了结构表征。通过循环伏安法（cyclic voltammetry, CV）考察了该类单体的氧化还原性能。与已有文献的普遍结论不同，Py4Fc与Py6Fc在电化学聚合过程中未损失二茂铁基团的氧化还原活性。此外，本研究将点击化学手段应用于聚合后功能化改性：首先电化学合成了三种含叠氮基的聚吡咯P(Py3N3)、P(Py4N3)与P(Py6N3)，随后使其与乙炔基二茂铁发生点击化学反应。对经聚合后功能化改性的聚合物进行循环伏安测试发现，其均呈现准可逆氧化还原峰；仅P(Py6-post-Fc)同时表现出聚吡咯与二茂铁的特征氧化还原行为。综上，本研究成功制备了共价键合二茂铁单元的吡咯导电均聚物，并考察了间隔基团对聚合物性能的影响。