CO electro-oxidation by carbon-supported Rh tetraphenylporphyrins that have o-methyl groups on meso-phenyl substituents

The ortho-methyl groups on meso-phenyl substituents were shown to strongly inhibit CO oxidation by Rh tetraphenylporphyrins. When both of the ortho-positions were occupied by methyl groups, CO oxidation was dramatically inhibited. The CO adduct was characterized by spectroscopy. O2 reduction by Rh tetraphenylporphyrins with ortho-methyl groups on meso phenyl substituents was also examined. The effects of ortho-methyl groups on CO oxidation are discussed in terms of steric hindrance.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► We investigated electrochemical CO oxidation activity of Rh tetraphenylporphyrins. ► Ortho-methyl groups on meso phenyl groups strongly inhibit CO oxidation activity. ► The effect of ortho-methyl groups was also examined by spectroscopy. ► O2 reduction is not strongly inhibited by ortho-methyl groups. ► The results suggest that steric hindrance of ortho-methyl groups is important.