Magnetic field control of electron tunneling pathways in the monolayer of (ferrocenylmethyl)dodecyldimethylammonium bromide on a gold electrode.

The electron-tunneling reaction in the monolayer of (ferrocenylmethyl)dodecyldimethylammonium bromide (FDDA) and the mixed monolayer of FDDA and 11-mercaptoundecanoic acid (MUA) on gold electrodes was affected by homogeneous, steady magnetic fields perpendicular to the monolayer membrane. Both the current and peak-to-peak separation potential of the ferrocenyl/ferricenium redox couple in cyclic voltammograms increased with increasing magnetic field intensity. The electron tunneling reaction of FDDA depended not on the barrier thickness of the monolayer but on the electron tunneling pathways. The increase in the tilt angle of hydrocarbon chains of FDDA and MUA due to cooperative magnetic orientation may bring about change of the electron tunneling pathway of the through-bond to through-space. With increasing magnetic fields, the increase in the path length and interchain superexchange hops led to an increase in the peak-to-peak separation potential and tunneling current. The positive shift of the formal potential due to magnetic fields is ascribed to promotion of hydration around the redox couple.