We report for the first time that carbonyl meso-tetrakis(4-Nmethylpyridiniumyl)porphyrinatoruthenium(II) tetraacetate (Ru-TPyP) worked as a catalyst for the Belousov-Zhabotinsky (BZ) reaction. The profiles from the BZ reaction were measured by potentiometric measurements with a Pt electrode and a Hg/ HgNO 3 reference electrode. Ru-TPyP was added lastly to the aqueous solution containing malonic acid (MA), sodium bromate (NaBrO 3 ), and nitric acid (HNO 3 ) at 22 AE 2 8C. The oscillation of the BZ reaction was observed over a fixed period of time only in the solution containing 2.1 3 10 À2 M MA, 3.2 3 10 À2 M NaBrO 3 and 5.5 3 10 À2 M HNO 3 . The self-oscillation period in Ru-TPyP was approximately 100 s and it continued for approximately 2600 s.Self-oscillating systems are widespread in nature and are a key feature of space-time self-assembly of non-equilibrium systems. The Belousov-Zhabotinsky (BZ) reaction is the best known example of far-from-equilibrium self-organizing chemical reactions, such as in animal skin patterns, [1] brain waves, [2] heartbeats, [3,4] and cells [5] , and neurons. [6] The BZ reaction is an oscillation reaction involving the catalyzed oxidation of an organic substrate such as malonic acid by sodium bromate in an acidic solution. Conventional catalysts for this reaction [7] are Ce (III/IV) ions, Mn(II/III) ions, Ru(bpy) 3 (II/III), and ferroin (II/III), which do not exist in living organisms. Metalloporphyrins play an important role in biochemistry, [8] for example, protoporphyrin IX in heme and iron complexes in hemoglobin and myoglobin. However, the use of metalloporphyrins as catalysts in BZ reactions has not yet been attempted. Here, we report a BZ reaction catalyzed by metalloporphyrins for the first time.First, water-soluble metalloporphyrins were prepared because the BZ reaction has been conventionally examined in acidic aqueous systems (Figure 1). Ruthenium porphyrin complexes were prepared from meso-tetrapyridylporphyrin (H 2 -TPyP) and meso-tetrakis(4-sulfonatophenyl)porphyrin (H 2 -TPPS) according to the reported procedure. [9] The BZ reaction was performed as follows. [10] The initial concentrations of malonic acid (MA) and metalloporphyrin were fixed at 2.1 3 10 À2 M and 2.9 3 10 À4 M, respectively, whereas the initial concentrations of sodium bromate (NaBrO 3 ) and nitric acid (HNO 3 ) were varied as shown in Table 1. The oscillation was examined when the four substrates were mixed. The profiles from the BZ reaction were measured by potentiometric measurements with a Pt electrode and a Hg/HgNO 3 reference electrode, accompanying a periodic oscillation of the redox potential of the metal catalyst (see supporting information, Figure S1). [11] In all experiments, the metalloporphyrin was added lastly to the aqueous solution containing MA, NaBrO 3 , and HNO 3 at 22 AE 2 8C, and then, the oscillation was monitored (Table 1). As for Ru-TpyP, the concentrations of NaBrO 3 and HNO 3 were varied in the range 1.6 -6.4 3 10 À2 M and 2.7 -9.5 3 10 À2 M, respectively.
