Institute for Chemical Research, Kyoto University, Uji 611-0011, Japan.
J Am Chem Soc. 2011 Jun 1;133(21):8354-61. doi: 10.1021/ja2020668. Epub 2011 May 4.
[n]Cycloparaphenylenes (n = 8-13, CPPs) were synthesized, and their physical properties were systematically investigated. [8] and [12]CPPs were selectively prepared from the reaction of 4,4'-bis(trimethylstannyl)biphenyl and 4,4''-bis(trimethylstannyl)terphenyl, respectively, with Pt(cod)Cl(2) (cod = 1,5-cyclooctadiene) through square-shaped tetranuclear platinum intermediates. A mixture of [8]-[13]CPPs was prepared in good combined yields by mixing biphenyl and terphenyl precursors with platinum sources. Products were easily separated and purified by using gel permeation chromatography. In (1)H NMR spectra, the proton of the CPPs shifts to a lower field as n increased due to an anisotropic effect from the nearby PP moieties. Although the UV-vis spectra were rather insensitive to the size of the CPPs, the fluorescence spectra changed significantly in relation to their size. A larger Stokes shift was observed for the smaller CPPs. Redox properties of the CPPs were measured for the first time by using cyclic voltammetry, and the smaller CPPs had lower oxidation potentials. The results are consistent with the HOMO energies of CPPs, of which the smaller CPPs had higher energies.
[n]环并苯（n = 8-13，CPPs）被合成，并对其物理性质进行了系统研究。[8]和[12]CPPs分别通过 Pt(cod)Cl(2)（cod = 1,5-环辛二烯）与 4,4'-双（三甲基锡基）联苯和 4,4''-双（三甲基锡基）三联苯之间的正方形四核铂中间体选择性制备。通过混合联苯和三联苯前体与铂源，以良好的总收率制备了[8]-[13]CPPs 的混合物。通过凝胶渗透色谱很容易分离和纯化产物。在（1）H NMR 谱中，由于附近的 PP 部分的各向异性效应，CPP 的质子向更低的磁场移动。尽管 UV-vis 光谱对 CPP 的大小相当不敏感，但荧光光谱与它们的大小有显著变化。较小的 CPPs 观察到较大的斯托克斯位移。首次通过循环伏安法测量 CPPs 的氧化还原性质，较小的 CPPs 具有较低的氧化电位。结果与 CPPs 的 HOMO 能量一致，较小的 CPPs 具有更高的能量。
