作者:Alexander Hildebrandt、Heinrich Lang
DOI:10.1039/c1dt10997a
日期:——
Functionalised diferrocenyl-1-phenyl-1H-pyrroles were synthesised using Negishi C,C cross-coupling reactions. The influence of different substituents at the phenyl moiety on the electronic interaction was studied using electrochemistry (cyclic and square-wave voltammetry) and spectro-electrochemistry (in situ UV/Vis-NIR spectroscopy). The ferrocenyl moieties gave rise to two sequential, reversible redox processes in each of the diferrocenyl-1-phenyl-1H-pyrroles. The observed ΔE1/2 values (ΔE1/2 = difference between first and second oxidation) range between 420 and 480 mV. A linear relationship between the Hammett constants σ of the substituents and the separation of the redox potentials exists. The NIR measurements confirm electronic communication between the iron centers as intervalence charge transfer (IVCT) absorptions were observed in the corresponding mixed-valent monocationic species. All compounds were classified as class II systems according to Robin and Day (M. B. Robin and P. Day, Adv. Inorg. Chem., 1967, 10, 247–423). The oscillator strength of the charge transfer transition highly depends on the electron donating or electron withdrawing character of the phenyl substituents. This enables direct tuning of the intermetallic communication by simple modification of the molecule's functional group. Hence, this series of molecules may be regarded as model compounds for single molecule transistors.
使用Negishi C,C交叉偶联反应合成了功能化的双铁酸酰基-1-苯基-1H-吡咯。研究了不同取代基对苯基部分电子相互作用的影响,使用了电化学(循环伏安法和方波伏安法)和光谱电化学(原位UV/Vis-NIR光谱)。铁酸酰基部分在每个双铁酸酰基-1-苯基-1H-吡咯中引发了两个连续的、可逆的氧化还原过程。观察到的ΔE1/2值(ΔE1/2 = 第一次和第二次氧化之间的差值)在420mV到480mV之间。取代基的Hammett常数σ与氧化还原电位之间的间隔呈线性关系。NIR测量证实了铁中心之间的电子通讯,因为在相应的混合价单阳离子物种中观察到了间层电荷转移(IVCT)吸收。根据Robin和Day的分类(M. B. Robin和P. Day,Adv. Inorg. Chem.,1967,10,247-423),所有化合物被归类为二类系统。电荷转移跃迁的振幅强度高度依赖于苯基取代体的给电子或吸电子特性。这使得通过简单修改分子功能团直接调节金属间的通讯成为可能。因此,这一系列分子可以被视为单分子晶体管的模型化合物。