Abnormal Magnetic Field Effects on Electrogenerated Chemiluminescence

We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFE(ECL)) based on triplet emission from the Ru(bpy)(3)Cl(2)-TPrA electrochemical system: the appearance of MFE(ECL) after magnetic field ceases. In early studies the normal MFE(ECL) have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFE(ECL) suggest that the activated charge-transfer [Ru(bpy)(3)(3+) … TPrA(•)] complexes may become magnetized in magnetic field and experience a long magnetic relaxation after removing magnetic field. Our analysis indicates that the magnetic relaxation can gradually increase the density of charge-transfer complexes within reaction region due to decayed magnetic interactions, leading to a positive component in the abnormal MFE(ECL). On the other hand, the magnetic relaxation facilitates an inverse conversion from triplets to singlets within charge-transfer complexes. The inverse triplet → singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFE(ECL). The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFE(ECL) after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer [Ru(bpy)(3)(3+) … TPrA(•)] complexes in solution at room temperature.