Magnetic field effects on photoelectrochemical reactions of porphyrin-viologen linked compounds in an ionic liquid

Magnetic field effects (MFEs) on photoelectrochemical reactions of three porphyrin-viologen linked compounds with various methylene groups [ZnP(n)V (n = 4,6,8)] were examined in 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF₄]) as an ionic liquid using a two-electrode cell. Stable anodic photocurrents are produced by irradiating ZnP(n)V (n = 4,6,8) in [BMIM][BF₄] with visible light, and the MFEs on photocurrents were clearly observed in ZnP(n)V (n = 4,6,8). The MFEs on photocurrents increase with magnetic field for lower magnetic fields (6 ≤ 200 mT) and are constant for higher magnetic fields (6 > 200 mT). The magnitude of the MFEs in ZnP(n)V (n = 6,8) are larger than that in ZnP(4)V. The MFEs can be explained by radical pair mechanism. The magnitude of the MFEs is larger than those in electrodes modified with ZnP(n)V (n = 4,6,8) as Langmuir-Blodgett films. The results are most likely attributable to the properties of [BMIM][BF4] and the mechanism of photoelectrochemical reaction.