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Pure Appl. Chem., 2009, Vol. 81, No. 12, pp. 2253-2263

Published online 2009-11-15

Formation of (FeCl3)@phenylazomethine dendrimer (DPA): Fine control of the release and encapsulation of Fe ions in dendrimers

Kimihisa Yamamoto1*, Reina Nakajima1, Yousuke Ochi1, Masanori Tsuruta1, Masayoshi Higuchi1, Akira Hida2 and Jun Onoe2

1 Department of Chemistry, Faculty of Science and Technology, Keio University, Yokohama 223-8522, Japan
2 Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro, Tokyo 152-8550, Japan

Abstract: Phenylazomethine dendrimers (DPAs) act as a strong coordination site for metal ion assembly. DPA G4 is regarded as a molecular capsule having 30 metal-assembling sites with a 2.7 nm diameter. We have reported the radial stepwise complexation with Sn2+ ions in the dendrimers, which means the location and number of metal ions can be controlled. Therefore, DPA G4 should realize a ferritin-like redox nanocapsule with precise control of the number of Fe ions. On the other hand, the Fe ion is a typical paramagnetic molecule. For creating an advanced memory with a high density, ferritin is one of the candidates for use as a magnetic quantum dot. Many attempts to use biomaterials, for example, ferritins and chapero-nins, as metal storage capsules have been demonstrated. Some research groups fabricate a device by assembling ferritins on a plate using their rigid and uniform structure. The attempts to use dendrimers have also been demonstrated. We now describe the successful attempt to control the "encapsulation and release" of iron ions in a dendrimer in order to mimic a ferritin through the redox reaction. Furthermore, the assembling structures of (FeCl3)n@DPA on a plate were first observed by scanning tunneling microscopy (STM) as a dendrimer complex, which shows that a highly oriented film is formed on a plate only by solvent casting.