Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790-8577, Japan.
Chemistry. 2010 Apr 6;16(13):4063-74. doi: 10.1002/chem.200903196.
Tetrameric porphyrin formation of 2-hydroxymethylpyrrole fused with porphyrins through a bicyclo[2.2.2]octadiene unit gave bicyclo[2.2.2]octadiene-fused porphyrin pentamers. Thermal conversion of the pentamers gave fully pi-conjugated cruciform porphyrin pentamers fused with benzene units in quantitative yields. UV/Vis spectra of fully pi-conjugated porphyrin pentamers showed one very strong Q absorption and were quite different from those of usual porphyrins. From TD-DFT calculations, the HOMO level is 0.49 eV higher than the HOMO-1 level. The LUMO and LUMO+1 levels are very close and are lower by more than 0.27 eV than those of other unoccupied MOs. The strong Q absorption was interpreted as two mutually orthogonal single-electron transitions (683 nm: 86 %, HOMO-->LUMO; 680 nm: 86 %, HOMO-->LUMO+1). The two-photon absorption (TPA) cross section value (sigma((2))) of the benzene-fused porphyrin pentamer was estimated to be 3900 GM at 1500 nm, which is strongly correlated with a cruciform molecular structure with multidirectional pi-conjugation pathways.
通过双环[2.2.2]辛二烯单元将 2-羟甲基吡咯与卟啉融合，形成四聚卟啉，得到双环[2.2.2]辛二烯融合卟啉五聚体。五聚体的热转化以定量产率得到完全π共轭的十字形卟啉五聚体，其苯环单元融合。完全π共轭卟啉五聚体的紫外可见光谱显示出一个非常强的 Q 吸收，与通常的卟啉有很大不同。从 TD-DFT 计算来看，HOMO 能级比 HOMO-1 能级高 0.49 eV。LUMO 和 LUMO+1 能级非常接近，比其他未占据 MO 低 0.27 eV 以上。强 Q 吸收可解释为两个相互正交的单电子跃迁（683nm：86%，HOMO->LUMO；680nm：86%，HOMO->LUMO+1）。苯融合卟啉五聚体的双光子吸收（TPA）截面值（sigma((2)))在 1500nm 时估计为 3900GM，这与具有多向π共轭途径的十字形分子结构密切相关。
