Magnetic field enhanced charge conduction in paramagnetic nickel(ii)–cysteine heterostructures†

Abstract

A chiral ligand, known as a symmetry-breaking reagent, can induce chirality in many achiral objects, including inorganic materials, for probing organic–inorganic interfaces, chiroptics, chirality induced spin-selectivity, and magneto-electrochemical phenomena. Chirality-induced paramagnetic heterostructures have not yet been explored in magneto-electrochemical and energy applications. Herein, we demonstrated the ability of L- and D-cysteines to transfer chirality in achiral and paramagnetic nickel(II) heterostructures. A red shift occurred in the circular dichroism spectra of L- and D-Cys-Ni(II) heterostructures compared to those of free L- or D-Cys, which was a clear indication of chirality transferred in paramagnetic nickel, a signature of chiroptical phenomena. Two-terminal electronic devices of heterostructure assemblies revealed approximately 50% of enhancement in their electrical current, which was caused by an external magnetic field of 350 mT within a DC potential range of ±0.8 V. The chiral materials showed a nearly 58–85% enhanced faradaic current in response to an external magnet placed underneath the L- and D-Cys-Ni(II)-modified working electrodes in an electrochemical cell. This enhancement in either the solid-state or magneto-electrochemical effect was attributed to the presence of paramagnetic Ni(II) ions that experienced a magnetic field, reducing charge transfer resistance. A chiral potential and spin–orbit coupling in chiral heterostructures significantly contributed to spin momentum, which enhanced charge conduction. This work highlights the importance of surface engineering in chirality transfer, which is sensitive to electrical conductivity and external magnetic fields.