CHEMICAL EFFECTS OF CHARGE-TRANSFER ABSORPTION .I. PHOTOINDUCED CHAIN REACTION BETWEEN THALLIUM(1) AND THALLIUM(3)

Ultraviolet irradiation of 204Tl-labeled thallium(I)-thallium(III) solutions induces rapid exchange with quantum yields ranging from 2 to 30 or higher. Initiation is due to charge-transfer absorption in Tlaq3+ and TlOH2+ producing a thallium(II) chain carrier. Rate constants for the propagation reactions of thallium(II) with thallium(I) and thallium(III) are derived. Chain termination is largely quadratic disproportionation of thallium(II), but at low light intensities, a linear termination reaction is more important. The relevance of these observations to the thermal mechanism for thallium(I)-thallium(III) exchange is discussed.