Photochemical oxidation of hydrocarbons using molecular oxygen as oxidant and Sn(lV)-or Sb(V)-porphyrin Abstract: as photosensitizer to generate the required co-reductant is described. Fe(lll)-or Mn(lll)-porphyrin is the hydrocarbonoxidation catalyst. The system is long-lived and may be used in photo-initiated spectroscopic kinetic studies. A great variety of alkane and olefin oxidation systems that mimic biological oxidation of hydrocarbons by cytochrome P,,, have been reported. I-8 Most use an iron, manganese, or ruthenium porphyrin as the analog of the heme (iron porphyrin) functional group of the enzyme. In the great majority of these chemistries a single oxygen atom imidezole binding as a fiih ligand acts as a promoter for P,,, reaction as has been noted in earlier studies'l Both of these results support the contention that the reaction is occuriig at the porphyrin catalyst under these conditions. Most importantly, when the FeP catalyst is present in the dark reaction the product ratio is one or less. Therefore, the dark reaction appears to compete favorably with the singlet 0, reaction in the photochemical reaction as shown in Scheme 1. The dark reaction results in the observed lowering in the alcohol/ketone ratio and higher yield measured in the presence of the FeP catalyst. Also, viologen appears not to aid the reaction, since the yield generally remains unchanged or is lowered in its presence (data not shown). This is also true of the dark reaction (Table 2). In summary, a photochemically driven reaction that mimics biological photosynthesis, electron-transfer, and hydrocarbon-oxidation reactions has been described. The reaction occurs et room temperature and uses 0, as the oxidant. Further studies are underway to determine the detailed reaction mechanisms involved in the photochemical reaction. Transient absorption and Ratnan spectrocopic techniques will also be applied to determine reaction rates.
Acknowledaements.