Hogan Conor F, Harris Alexander R, Bond Alan M, Sly Joseph, Crossley Maxwell J
Department of Chemistry, La Trobe University, Bundoora, Victoria, 3086, Australia.
Phys Chem Chem Phys. 2006 May 7;8(17):2058-65. doi: 10.1039/b516281e. Epub 2006 Mar 24.
The electrochemical properties of porphyrin-appended dendrimers containing 2-, 4-, 8-, 16-, 32- and 64-porphyrin macrocycles in their free-base and zinc(II) forms have been investigated. Both series gave diffusional based voltammetric responses in dichloromethane. There was minimal effect of dendrimer generation on the redox potentials. Multiple pi-cation and anion radicals as well as dications and dianions were formed on the surface of the dendrimers on oxidation or reduction as appropriate, with each cyclic voltammetric wave representing electron transfer to or from multiple non-interacting porphyrin sites. Electrostatic interactions in the higher generation dendrimers result in kinetic effects being observed for the highly charged species generated when each porphyrin unit is doubly or triply oxidised. The number of electrons transferred on reduction or oxidation of the dendrimers was evaluated using steady-state microelectrode voltammetry. For the lower generations of species a good correlation was observed between numbers of electrons transferred and number of porphyrin entities per molecule; for the dendrimers containing 32 and 64 units, however, slight negative deviations were observed, possibly due to electrostatic interactions as the porphyrins become closer packed.
研究了在其游离碱和锌（II）形式中含有2、4、8、16、32和64个卟啉大环的卟啉连接树枝状大分子的电化学性质。这两个系列在二氯甲烷中均给出基于扩散的伏安响应。树枝状大分子代数对氧化还原电位的影响最小。在树枝状大分子表面进行适当的氧化或还原时，会形成多个π阳离子和阴离子自由基以及二价阳离子和二价阴离子，每个循环伏安波代表电子向多个非相互作用的卟啉位点转移或从其转移。在较高代数的树枝状大分子中，静电相互作用导致当每个卟啉单元被双重或三重氧化时产生的高电荷物种出现动力学效应。使用稳态微电极伏安法评估树枝状大分子在还原或氧化时转移的电子数。对于较低代数的物种，观察到转移的电子数与每个分子中卟啉实体的数量之间有良好的相关性；然而，对于含有32和64个单元的树枝状大分子，观察到轻微的负偏差，这可能是由于随着卟啉堆积得更紧密而产生的静电相互作用。
