Attempts To Observe Spin Catalysis by Paramagnetic Particles in the Photolysis of 7-Silanorbornadiene in Solution

Abstract

Addition of the stable radical, 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-OH-TEMPO), to the reaction mixture in the photolysis of 7-silanorbornadiene in solution results in the decrease of the magnetic field effect detected for the yield of stable reaction product, tetraphenylnaphthalene (TPN). The dependence of TPN yield on 4-OH-TEMPO concentration obeys the Stern−Volmer equation; the estimated rate constant of the quenching of triplet dimethylsilylene by the stable radical is kTEMPO = 1.4 × 108 M-1. In accordance with the suggested hypothesis, the paramagnetic additivesthe stable radical and O2, which has been studied earlierchange the T−S conversion rate in the intermediate biradicals via the so-called spin catalysis mechanism.