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Cobalt(ii)-tetraphenylporphyrin (CoVpp)-fixed glassy carbon (GC) electrodes were prepared using 4-aminopyridine (pyNH2) in the form of Colltpp-pyNH-CO/GC, which were active for electroreduction of C 0 2 to CO at potentials 100 mV more positive than water-soluble Coil porphyrins, and the overall turnover number of Coiltpp for CO production exceeded 105.Metalloporphyrins have been reported to be active as catalysts in the electroreduction of C 0 2 in aqueous' and nonaqueous2 media. In aqueous media, water-soluble CoIItetraphenylporphyrin sulphonate and CoTTrneso-tetracarboxyphenylporphyrin have been reported to be catalytically active for the electroreduction of C 0 2 . Pyridine (py) is reported to coordinate at the axial position of planar CoII(sa1en) (H2salen = bissalicylideneethylenediamine) and stabilizes C 0 2 in the opposite coordination site.3 In the present work, we attempted to obtain a CoIItpp-py (tpp = tetraphenylporphyrin) complex-fixed electrode by applying the water-insoluble CoIItpp on glassy carbon (GC) substrate plates modified initially with 4-aminopyridine (pyNH2). 4-Aminopyridine is expected not only to immobilize CoIItpp on the G C electrode, but also to provide the CoIItpp-fixed GC electrode with new properties.CoIItpp-pyNH-CO/GC (I) was prepared as follows Glassy carbon (GC) plates (Tokai GC-30, 27 mm x 5 mm, 1 mm thick) were subjected to anodic oxidation in 0.5 mol dm-3 H2S04, and refluxed in SOC12 for 24 h, for chlorination as COCl/GC. The electrodes were then immersed in 4-aminopyridine-saturated benzene solution for 24 h at room temperature to produce pyNH-CO/GC (11). Finally, the electrodes were refluxed in a 0.6 mmol dm-3 CoIItpp solution in benzene for 24 h to produce I.The fixation of 4-aminopyridine was confirmed by the diffuse reflectance FT IR spectrum of 11, which showed a peak at 1665 cm-1 due to C=O stretching of the -CO-NH-amide group together with pyridine ring C=C and C=N stretching peaks at 1610 and 1537 cm-1, respectively. These results showed that 4-aminopyridine was fixed in the form of pyNH-CO/GC. Fig. l(a) shows the diffuse reflectance UV-VIS spectrum of I, together with spectra of ( b ) CoIItpp and (c) CoIItpp-py in CH2C12 for comparison. Spectra ( a ) and (c) show the Soret band at 440 nm, whereas that of ( b ) is at 420 nm. These spectra indicated that Co**tpp was fixed as the pyridine complex, CoIItpp-py, and the electron density of the central ColI ions of I was increased by the pyridine 1igand.s Fig. 2 shows cyclic voltammograms (CV) of I in standard phosphate buffer solution at pH 6.86 saturated with He or C02. No CoIItpp/CoItpp redox peak was observed, but this is probably due to the small amount of CoIItpp distributed on the electrode which has a high roughness factor (3 x 103). The surface concentration of CoIItpp of (10-12 mol cm-2; apparent surface area) was evaluated by ESCA. A pronounced increase of the cathodic current was observed at potentials more negative than -0.95 V [vs. saturated calomel electrode (SCE)] in C02-saturated solution, this increase st...

D-Mannitol, one of the main phytochemicals of the edible Tamogi-take mushroom (Pleurotus cornucopiae), was found to inhibit an angiotensin I converting enzyme (ACE). The antihypertensive effect of D-mannitol and a hot water extract of Tamogi-take mushroom was demonstrated in spontaneously hypertensive rats (SHR) by oral administration.

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