Magnetic field effects and CIDEP due to the d-type triplet mechanism in intra-molecular reactions

In this review, we present an overview of magnetic field effects (MFEs) and chemically induced electron polarization (CIDEP) due to the d-type triplet mechanism (TM) in intra-molecular reactions of photo-excited triplet molecules. Because the conditions for such MFEs and CIDEP are rather strict, they had been observed only for a few types of radicals generated through triplet exciplexes of some excited dye molecules with heavy-atom substituted electron donors in polar solvents, until quite recently. Under such circumstances, Paul's group and that of the present authors have recently found MFEs and CIDEP due to the d-type TM for intra-molecular reactions from photo-excited triplet states of azoalkanes and triarylphosphines, respectively, irrespective of solvent polarity. These studies have extended the research field of the d-type TM from very limited reactions through triplet exciplexes to more general intra-molecular ones of triplet molecules. In the present review, we would like to summarize the various mechanisms for MFEs and CIDEP, to explain a theory for MFEs and CIDEP due to the d-type TM, and to present the new advances obtained experimentally by the two groups.