We report abnormal magnetic field effects on electrogenerated chemiluminescence (MFEECL) based on triplet emission from the Ru(bpy)3Cl2-TPrA electrochemical system: the appearance of MFEECL after magnetic field ceases. In early studies the normal MFEECL have been observed from electrochemical systems during the application of magnetic field. Here, the abnormal MFEECL suggest that the activated charge-transfer [Ru(bpy)33+… 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 MFEECL. 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 MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL 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)33+… TPrA•] complexes in solution at room temperature.
(a) MFEECL are generated by density and conversion channels due to Lorentz and magnetizing force exerting on magnetized activated [A−… D+] complexes and spin mixing between singlet 1[A−… D+] and triplet 3[A−… D+] complexes, respectively. (b) The reaction routes are shown for the formation of charge-transfer [Ru(bpy)33+… TPrA•] complexes. The molecular structures are also shown for Ru(bpy)32+ and TPrA. The R and R′ denote CH2CH2CH3 and CH2CH3.
(a) MFEECL and MC are shown at a constant electrode-potential of 1.28 V rapidly changed from low 1.11 V. (b) Experimental setup for MFEECL/MC measurements by placing an electrochemical cell in a magnetic field. (c) Activated charge-transfer (CT) [Ru(bpy)33+… TPrA•] complexes are subject to both diffusion and magnetizing forces in reaction zone. Removing an external magnetic field can break the previously established equilibrium on the CT density, consequently leading to an increase on the mass transport of reactants with the consequence of increasing the CT density. (d) Schematic diagram to show the generation of abnormal MFEECL through density and conversion channels. [CT]B and [CT]0 are the densities of charge-transfer [Ru(bpy)33+… TPrA•] complexes upon applying and removing a magnetic field.
Figure 3: MC from two different electrochemical systems: (Ru(bpy)3Cl2 + TPrA) and TPrA with the same applied electrode potential of 1.28 V.
The two systems both use sodium dihydrogen phosphate as supporting electrolyte. The (Ru(bpy)3Cl2 + TPrA) system contains 1 mM Ru(bpy)3Cl2 and 0.08 M TPrA as reactants. The TPrA system contains only 0.08 M TPrA as reactant.
singlet conversion reduces the density of triplet light-emitting states through charge-transfer complexes and gives rise to a negative component in the abnormal MFEECL. The combination of positive and negative components can essentially lead to a non-monotonic profile in the abnormal MFEECL after ceasing magnetic field. Nevertheless, our experimental studies may reveal un-usual magnetic behaviors with long magnetic relaxation from the activated charge-transfer 
![MC from two different electrochemical systems: (Ru(bpy)3Cl2 + TPrA) and TPrA with the same applied electrode potential of 1.28[emsp14]V.](http://www.nature.com/srep/2015/150316/srep09105/carousel/srep09105-f3.jpg)
