Department of Material and Life Science, Division of Advanced Science and Biotechnology, Graduate School of Engineering, Osaka University, SORST, Japan.
J Am Chem Soc. 2010 Mar 31;132(12):4477-89. doi: 10.1021/ja100192x.
A novel porphyrin tripod (TPZn(3)) was synthesized via "click chemistry". Three porphyrin moieties of TPZn(3) are geometrically close and linked by a flexible linker. The electron-transfer oxidation of TPZn(3) results in intramolecular pi-dimer formation between porphyrin moieties as indicated by electrochemical, vis-NIR, and ESR measurements. The cyclic voltammogram of TPZn(3) exhibited stepwise one-electron oxidation processes of three porphyrin moieties in the range from 0.58 to 0.73 V (vs SCE in CH(2)Cl(2)). When TPZn(3) was oxidized by tris(2,2'-bipyridyl)-ruthenium(III) (Ru(bpy)(3)), the oxidized species (TPZn(3))(n+) (0 < n </= 3) exhibited a charge resonance band in the NIR region due to the pi-dimer formation between porphyrin moieties. A supramolecular electron donor-acceptor system was also constructed using TPZn(3). The flexible conformation of TPZn(3) makes it possible to capture a fullerene derivative containing a pyridine moiety (PyC(60)) inside the cavity by pi-pi interactions as well as the coordination bond between Zn(2+) and the pyridine moiety. The formation of a 1:1 supramolecular complex of TPZn(3) with PyC(60) (TPZn(3)-PyC(60)) was indicated in the UV-vis and (1)H NMR spectra in nonpolar solvents. The association constant of TPZn(3) with PyC(60) (1.1 x 10(5) M(-1) in toluene) is much larger as compared with those of the corresponding monomer (MPZn) and dimer porphyrin (DPZn(2)). The dynamics of photoinduced electron transfer from the singlet excited state of TPZn(3) to PyC(60) was examined by laser flash photolysis measurements. The efficient intracomplex photoinduced electron transfer in TPZn(3)-PyC(60) occurred in nonpolar solvents, resulting from the pi-pi interactions between the porphyrin and fullerene moieties, together with intramolecular pi-bond formation between the porphyrin radical cation and the neutral porphyrin in TPZn(3)(*+).
一种新型卟啉三脚架（TPZn(3)）通过“点击化学”合成。TPZn(3) 的三个卟啉部分在几何上接近，并通过柔性连接体连接。TPZn(3) 的电子转移氧化导致卟啉部分之间形成分子内π-二聚体，这可以通过电化学、可见-近红外和 ESR 测量来指示。TPZn(3) 的循环伏安图显示了三个卟啉部分在 0.58 至 0.73 V（相对于 SCE 在 CH(2)Cl(2)中）范围内的逐步单电子氧化过程。当 TPZn(3) 被三（2,2'-联吡啶）-钌（III）(Ru(bpy)(3))氧化时，氧化物种(TPZn(3))(n+)（0 < n < = 3）在近红外区域显示出电荷共振带，这是由于卟啉部分之间的π-二聚体形成。还使用 TPZn(3)构建了超分子给体-受体体系。TPZn(3) 的柔性构象使其能够通过π-π相互作用以及 Zn(2+)和吡啶部分之间的配位键，将含有吡啶部分的富勒烯衍生物（PyC(60)）捕获到空腔中。在非极性溶剂中，TPZn(3)与 PyC(60)（TPZn(3)-PyC(60)）的 1:1 超分子配合物的形成在 UV-vis 和 (1)H NMR 光谱中得到了表明。与相应的单体（MPZn）和二聚体卟啉（DPZn(2)）相比，TPZn(3)与 PyC(60)的缔合常数（在甲苯中为 1.1 x 10(5) M(-1)）要大得多。通过激光闪光光解测量研究了从 TPZn(3)的单重激发态到 PyC(60)的光诱导电子转移的动力学。在非极性溶剂中，TPZn(3)-PyC(60)中发生了有效的内配合物光诱导电子转移，这是由于卟啉和富勒烯部分之间的π-π相互作用，以及 TPZn(3)(*+)中卟啉自由基阳离子和中性卟啉之间的分子内π键形成。
