Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, USA.
J Org Chem. 2009 Dec 18;74(24):9475-85. doi: 10.1021/jo902109u.
Whereas encapsulation of functional groups at the core of dendrimers is well-understood, very little is known about their intermediate layers or even the periphery. Here we report on a systematic investigation of every layer of dendrimers by incorporating a single ferrocene unit in well-defined locations in dendrons. Site-specific incorporation of the ferrocene unit was achieved by utilizing the dendrimer sequencing methodology. We show here that the redox potential values of ferrocene at intermediate layers were remarkably different from those at the core and the periphery. Although redox potential values were location-dependent, no significant change in the rate of heterogeneous electron transfer (k(0)) was observed with respect to locations. This was attributed to the possibility that free rotation of dendrimer nullifies the distance between the electrode and ferrocene unit. Finally, we also show that no Faradaic current was observed for the amphiphilic assemblies of these dendrons, whereas the same dendron did exhibit significant Faradaic current in nonassembling solvent environments.
虽然树状大分子核心官能团的封装已得到很好的理解，但对于它们的中间层甚至外围，人们知之甚少。在这里，我们通过在树枝状分子中确定的位置引入单个二茂铁单元，对树状大分子的每一层进行了系统的研究。通过利用树状大分子排序方法实现了二茂铁单元的特异性引入。我们在这里表明，中间层中二茂铁的氧化还原电位值与核心和外围的氧化还原电位值显著不同。尽管氧化还原电位值与位置有关，但对于位置，观察到的非均相电子转移（k(0)）速率没有明显变化。这归因于树状大分子的自由旋转使电极和二茂铁单元之间的距离无效的可能性。最后，我们还表明，这些树枝状大分子的两亲组装体没有观察到法拉第电流，而在非组装溶剂环境中，相同的树枝状大分子则表现出显著的法拉第电流。
