Surface Photochemistry: On the Mechanism of the Semiconductor Photoinduced Valence Isomerization of Hexamethyl-Dewar Benzene to Hexamethylbenzene

Article abstract of DOI:10.1021/j100408a048

The CdS-, TiO2-, and ZnO-photoinduced valence isomerization of hexamethyl-Dewar benzene to hexamethylbenzene has been investigated in methylene dichloride solution and found to be very efficient.The reaction appears to follow modified Langmuir-Hinshelwood and Eley-Rideal mechanisms.A surface cation radical chain mechanism is proposed since the reaction can be efficiently quenched by electron donors, and quantum yields greater than unity were obtained in TiO2 and ZnO reactions.The quenching also followed modified Langmuir-Hinshelwood and Eley-Rideal pathways, in which the latter predominantly contributed to the owerall quenching rates.CdS of different origins with different surface areas, purities, and structures were used, and the rates varied by a factor of 2.3.None of these functions appear to play a dominant role in the rate of reaction.