Comproportionation in the reduction of pyridinium derivatives—a combined ESR and electrochemical study

Supramolecular Memristor Based on Bistable [2]Catenanes: Toward High-Density and Non-Volatile Memory Devices

The ever-increasing demand for data storage and neuromorphic computing calls for innovative, high-density solutions, such as resistive random-access memory (RRAM). However, the integration of resistive switching and rectification at the nanoscale remains a formidable challenge. In this study, we introduce a bistable [2]catenane-based supramolecular junction that simultaneously functions as a resistive switch and a diode. All supramolecular junctions are highly stable and reproducible over thousands of resistive switching cycles, because the nano-confinement of two mechanically interlocked rings can stabilize the radical states of pyridinium moieties under ambient conditions. The successful realization of supramolecular junctions in functionality with a thickness of approximately 2 nm presents a promising avenue for the development of molecule-scale based RRAM for a better solution to high density and energy efficiency.

One-Electron Reduction of an “Extended Viologen” p-Phenylene-bis-4,4‘-(1-aryl-2,6-diphenylpyridinium) Dication

One-electron reduction of the "extended viologen" dication 1 yields the red cation radical 2, characterized by strong near-IR absorption. It has been generated and studied by pulse radiolytic, electrochemical, redox titration, UV-visible, and electron paramagnetic resonance spectroscopic methods. All results are in agreement with a fully delocalized electronic structure for 2.

The reductive deposition of quaternary pyridinium corrosion inhibitor multilayers on glassy carbon electrodes

The redox behaviour of several quaternary pyridinium corrosion inhibitors ("Quats") at glassy carbon (GC) electrodes has been investigated in neutral aqueous solutions. The primary emphasis is on n-butyl-3-(N-octyl carbamyl)pyridinium bromide, one of the Quats determined to have very good corrosion inhibition properties based on parallel weight loss experiments. It is demonstrated that the reduction of the Quats, which occurs in a two-electron reaction at potentials negative of –1.0 V vs. SSCE, results in the formation of a neutral product. This forms a porous film on the electrode surface, with clusters that expand and thicken as more Quat deposits, as confirmed by atomic force microscopy. The film charge density reaches a maximum of ~4 mC/cm2, equivalent to more than 100 monolayers of Quat, after which no further Quat can be deposited, suggesting full surface coverage by a nonconducting product. The Quat multilayer can then be redissolved at potentials positive of ~ –0.2 V, during its oxidation back to its original solution-soluble form. Key words: quaternarized pyridinium compounds, reductive film deposition, glassy carbon, multilayer, corrosion inhibitors, cyclic voltammetry, AFM.