Spectral investigation of the interaction of carbon monoxide and dioxygen with low-temperature sublimates of Co(II) meso-tetraphenylporphyrinate: Evidences for oxidative catalysis

The interaction of carbon monoxide and dioxygen with low-temperature (T = 7 7 K) sublimates of cob alt(II) meso- tetraphenylporphyrinate (CoTPP) is stu died by IR spectroscopy using is otopically labeled compounds ((CO)-C-13 an d O-18(2)). The obtained data confirm the coordination of CO and O-2 with t he formation of axial complexes CoTPP L (L = O-2, CO) and the mixed complex O-2 CoTPP CO. The heating of the complex containing CO and O-2 to 150 K le ads to the appearance of lines in the IR spectrum corresponding to valence asymmetric (v(as)OCO) and degenerated deformation (delta OCO) vibrations of carbon dioxide. This is evidence for the oxidation of CO. The evacuation o f CO2 at a higher, but still low, temperature and the addition of a new por tion of CO and O-2 mixture lead to the formation of new portions of CO2. Th is demonstrates the catalytic character of the process. Only low-temperatur e sublimates have catalytic properties. Sublimates of CoTPP obtained on the surface at room or higher temperature demonstrate neither catalytic activi ty nor the ability to coordinate any amount of CO and O-2 sufficient for th e detection by spectroscopy.