Highly Pure Synthesis,Spectral Assignments,and Two‐Photon Properties of Cruciform Porphyrin Pentamers Fused with Benzene Units |
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| Authors: | Hiroki Uoyama Kil?Suk Kim Dr Kenji Kuroki Jae‐Yoon Shin Dr Toshi Nagata Dr Tetsuo Okujima Dr Hiroko Yamada Dr Noboru Ono Prof Dongho Kim Prof Hidemitsu Uno Prof |
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| Institution: | 1. Department of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, Matsuyama 790‐8577 (Japan), Fax: (+81)?89‐927‐5510;2. Spectroscopy Laboratory for Functional π‐Electronic System and Department of Chemistry, Yonsei University, Seoul 120‐749 (Korea), Fax: (+82)?2‐2123‐2434;3. National Institutes for Natural Sciences (NINS), Institute for Molecular Science (IMS), 5–1 Higashiyama, Myodaiji, Okazaki 444‐8787 (Japan), Fax: (+81)?564‐59‐5510 |
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| Abstract: | Tetrameric porphyrin formation of 2‐hydroxymethylpyrrole fused with porphyrins through a bicyclo2.2.2]octadiene unit gave bicyclo2.2.2]octadiene‐fused porphyrin pentamers. Thermal conversion of the pentamers gave fully π‐conjugated cruciform porphyrin pentamers fused with benzene units in quantitative yields. UV/Vis spectra of fully π‐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 (σ(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 π‐conjugation pathways. |
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| Keywords: | density functional calculations porphyrinoids retro‐Diels– Alder reaction spectroscopy two‐photon absorption |
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