Ookayama 2-12-1-NE-1,
Meguro-ku, Tokyo
152-8550, Japan
Room 701 (Prof.),
Room 702
(Associate Prof.),
Room 703 (Assistant Prof., Students)

TEL: +81-3-5734-
2240 (Room 701)
2239 (Room 702)
2759 (Room 703)
e-mail: ishitani@chem.,


  • (1)Improvement of potocatalysts for CO2reduction

    Development of CO2 reduction photocatalysts driven by light energy is very important to solve the global warming and energy crisis. We have improved such catalysts and suceeded in the synthesis of the most effective homogeneous photocatalyst (Fig. 1). Now, we are trying to reveal the whole reaction mechanisms of the CO2 reduction, and to combine the reduction with water oxidation in the same system.

    Fig. 1 The most effective photocatalyst for CO2 reduction.

  • (2)Photocatalysis of supramolecular metal complexes

    Photocatalysts possessing mulitifunctions were developed by linking several metal complexes with ligands (Fig. 2). By connecting functinal metal complexes, more effective or new functions are aimed.

    Fig. 2 Supramolecular Ru(II)-Re(I) complex exhibiting high ability of CO2reduction.

  • (3)New photoreaction of Re(I) complex and the application for fmetal-assembled complexes

    Photo-induced ligand exchange reaction of Re(I) complex was discovered and the mechanism has been investigated. Moreover, it was found that 1D-oligomeric and macrocyclic metal complexes could be formed by applying the ligand exchange reaction (Fig. 3 and 4).

    Fig. 3 1D-oligomeric metal complexes and the photophysical properties.

  • (4)New photocatalytic metal complex achieving only the two electron reduction

    While a lot of Photocatalytic reduction or oxidation reactions have been reported, most of them began with electron transfer, which caused some problems because of the radical species produced as reaction intermediates. We succeeded in the synthesis of multi-electron reduction photocatalyst which did not involve electron transfer. By adopting this photocatalytic system, selective hydride reductive of coenzyme NAD(P) was realized in the same product distribution as that of photosynthesis by plants. Improvement and application of the reduction system, such as asymetric reductive photocatalyst, is now in progress.

    Fig. 5 Photocatalyst affording the same product distribution
    as that of photosynthesis by plants.

  • (5)Reactivity of model compounds of reductive coenzyme NADPH coordinating to metal complex

    Reductive coenzyme NADPH produce in photosynthesis is used as a reduction agent for carbon fixation, and therefore, the reduction can be applicable by increasing the reduction ability of coenzyme NADPH and the model compounds. We found that Lewis bases, Ru(II) and Re(I) complexes, enabled NADPH model compounds to be more reductive significantly by the coordination, and we are investigating the mechanim and developing new asymmetric reduction.

  • (6)Manipulating properties of metal complexes by weak interaction between ligands

    Controlling properties of metal complexes are essential for adopting complexes as photocatalysts. For example, use of solar energy inevitably requires metal complexes absorbing longer wavelength light. Previously, the properties were modulated by changing electronic properties (introduction of electron-donating and electron-withdrawing groups), which resulted in the significant affect on the other properties accompanying decline of photocatalytic activity. In exploring new ways to tune properties, weak interaction between ligands was found to manipulate the ground and excited states of metal complexes. By the weak interaction, photocatalytic ability was increased to a large extent.

    Fig. 6 Control of photo-functions by using weak
    interaction between aromatic ligands

  • (7)Construction of artificial Z-scheme

    Most of practical photocatalysts absorb UV (minor in sunlight (5%)), and does not use visible light (major in sunlight) effectively. To realize the useful chemical reactions, such as reduction of CO2 by H2O, artificial Z-scheme is required similar to the natural system of photosynthesis of plants. We are challenging the construction of the system by hybridizing our metal complexes and semiconductors.

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