Three-Dimensionally Arranged Windmill and Grid Porphyrin Arrays by AgI-Promoted meso–meso Block Oligomerization
✍ Scribed by Aiko Nakano; Tomoko Yamazaki; Yoshinobu Nishimura; Iwao Yamazaki; Atsuhiro Osuka
- Book ID
- 102679181
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 861 KB
- Volume
- 6
- Category
- Article
- ISSN
- 0947-6539
No coin nor oath required. For personal study only.
✦ Synopsis
The syntheses of soluble windmill and grid porphyrin arrays through the Ag I -promoted coupling reaction of 1,4-phenylene-bridged linear porphyrin arrays, which are comprised of a central Zn II b-free porphyrin and flanking peripheral Ni II b-octaalkylporphyrins, are described. The coupling reaction is advantageous in light of its high regioselectivity occurring only at the meso-position of the Zn II b-free porphyrin as well as its easy extension to large porphyrin arrays. The windmill porphyrin arrays in turn serve as an effective substrate for further coupling reactions, to give three-dimensionally arranged grid porphyrin arrays. Further the grid porphyrin 12-mer (a tetramer of the linear porphyrin trimer) was also coupled to afford grid porphyrins (24mer, 36-mer, and 48-mer). These porphyrin arrays were isolated in a discrete form by repetitive GPC/HPLC (GPC gel-permiation chromatography). Competitive experiments with three linear porphyrin trimers bearing different peripheral metalloporphyrins (Zn II , Ni II , and Cu II ), and the trapping experiment of the radical cation at the peripheral porphyrin with AgNO 2 , suggested that an initial one-electron oxidation of the easily oxidizable peripheral Zn II b-octaalkylporphyrin with an Ag I ion and a subsequent endothermic hole transfer assist the generation of the radical cation at the central Zn II b-free porphyrin. In all Zn II -metallated windmill porphyrin arrays, the energy level of the S 1 state of the meso ± meso-linked diporphyrin core is lower than that of the peripheral porphyrins, thereby allowing an energy flow from the peripheral porphyrins to the central diporphyrin core; this has been confirmed by measurements of fluorescence lifetimes and picosecond time-resolved fluorescence spectra. The excitation energy transfer in the arrays encourages their potential use as an light-harvesting antenna.