Metal Assembly in Novel Dendrimers with Porphyrin Cores

T. Imaoka, H. Horiguchi, K. Yamamoto
J. Am. Chem. Soc. 2003, 125, 340-341.

Metal Assembly in Novel Dendrimers with Porphyrin Cores

A series of phenylazozmethine (DPA) dendrimers with a porphyrin core (PnH2) were synthesized by dehydration using TiCl4 from meso-tetrakis(4-aminophenyl)porphyrin and the DPA dendrons. The addition of SnCl2 to a dichloromethane/acetonitrile solution of dendritic cobalt porphyrin resulted in a stepwise spectral change. By using UV−vis spectroscopy to monitor the complexation of the P4CoIIICl until an equimolar amount of SnCl2 has been added, four changes in the position of the isosbestic point were observed during the addition of SnCl2. Titration results suggest that four different complexes are successively formed upon the SnCl2 addition and that the complexation proceeds in, not a random, but a stepwise fashion from the core imines to the terminal imines of P4CoIIICl. The electrochemical study reveals that their dendrimers with Tb ion act as a multielectron mediator in CO2 reduction at high applied potential on the electrode.

日経産業新聞 「球状分子で有機EL素子」

日経先端技術 「独自の球状分子で有機EL素子」

No.23

現代化学 「新しい有機-金属ハイブリッドナノ材料」

現代化学, 374, 8-10(2002)

日経BP

日刊工業 「電子移動を制御・新材料を創出」

朝日新聞 「電子・光集める高分子創出」

C & En News 「Tin ions add to dendrimer from the core out」

日経産業新聞 「金属を規則的に配置」

Stepwise radial complexation of imine groups in phenylazomethine dendrimers

K. Yamamoto, M. Higuchi, S. Shiki, M. Tsuruta, H. Chiba
Nature 2002, 415, 509-511.

Dendrimers are highly branched organic macromolecules with successive layers or ‘generations’ of branch units surrounding a central core. Organic–inorganic hybrid versions have also been produced, by trapping metal ions or metal clusters within the voids of the dendrimers. The unusual, tree-like topology endows these nanometre-sized macromolecules with a gradient in branch density from the interior to the exterior, which can give rise to an energy gradient that directs the transfer of charge and energy from the dendrimer periphery to its coreHere we show that tin ions, Sn2+, complex to the imine groups of a spherical polyphenylazomethine dendrimer in a stepwise fashion. This behaviour reflects a gradient in the electron density associated with the imine groups, with complexation in a more peripheral generation proceeding only after complexation in generations closer to the core has been completed. By attaching an electron-withdrawing group to the dendrimer core, we are able to change the complexation pattern, so that the core imines are complexed last. By further extending this strategy, it should be possible to control the number and location of metal ions incorporated into dendrimer structures, which might find uses as tailored catalysts or building blocks for advanced materials.

Nature, News & View 「One generation at a time」Nature, 415, 487-489(2002)

日本工業新聞 「デンドリマーを使い新材料構築ナノ技術」

神奈川新聞 「ナノ材料の創出に成功」