Effect of NMR magnetic field in chemical reactions monitored NMR in situ

Abstract

In 2014 we have demonstrated, for the first time, that an electrochemical reaction (Cu2+ electrodeposition) monitored in situ by low field NMR spectroscopy is much faster than the respective reaction performed ex situ. Therefore, this demostrate that NMR is not a passive technique, as previously considered, but has a strong influence on the kinetics of the electrochemical reaction. This effect was also observed when the copper electrodeposition reaction was performed using a unilateral NMR spectrometer.The explanation for the NMR effect on the electrochemical reactions rate comes from the Lorentz force. This force is observed when the sample is submitted to an electric and magnetic fields. The effect of a magnetic field on electrochemical studies is known for a long time and the first observation was registered in Faraday diaries. The magnetic field also acts when in reactions is performed wihtout electric field. This force is observed in the presence of strong magnetic field gradient and in the presence of a gradient of concentration of paramagnetic specie . Despite being known for long time in electrochemistry, only in the last decades the qualitative and quantity explanation of the phenomena were determined. This area of study is known as magnetoelectrochemistry or magnetoelectrolysis.Although the effect of NMR magnetic field in electrochemical reaction monitored in situ has been demonstrated with a paramagnetic ion (Cu2+), the effect of the magnetic field can also occur with diamagnetic substances and in the absence of electric field applied.Therefore, the objective of this research is to evaluate the effect of the magnetic field of low field NMR spectrometers (up to about 0.5 T) and high field NMR (above 9 T) in electrochemical reactions (with and without the application of Eelectric field) and in non-electrochemical reactions (AU)