Electrically Induced Mixed Valence Increases the Conductivity of Copper Helical Metallopolymers

Abstract

Controlling the flow of electrical current at the nanoscale typically requires complex top‐down approaches. Here, a bottom‐up approach is employed to demonstrate resistive switching within molecular wires that consist of double‐helical metallopolymers and are constructed by self‐assembly. When the material is exposed to an electric field, it is determined that ≈25% of the copper atoms oxidize from CuI to CuII, without rupture of the polymer chain. The ability to sustain such a high level of oxidation is unprecedented in a copper‐based molecule: it is made possible here by the double helix compressing in order to satisfy the new coordination geometry required by CuII. This mixed‐valence structure exhibits a 104‐fold increase in conductivity, which is projected to last on the order of years. The increase in conductivity is explained as being promoted by the creation, upon oxidation, of partly filled orbitals aligned along the mixed‐valence copper array; the long‐lasting nature of the change in conductivity is due to the structural rearrangement of the double‐helix, which poses an energetic barrier to re‐reduction. This work establishes helical metallopolymers as a new platform for controlling currents at the nanoscale.

Self-Assembly of Double-Helical Metallopolymers

“…67−69 The resistive switching behavior is exemplified when the measured current at 1 V was compared before and after electrically poling the device at 60 V. This experiment revealed a 10 4 -fold increase in conductivity after poling at 60 V, with a decay back to the initial state projected to occur on the order of years. 4 We investigated the origin of this resistive switching at the molecular level using in situ electron spin resonance (ESR). This setup allowed us to electrically pole a film of 6 inside the magnet and record the ESR spectrum immediately afterward without moving the sample in the microwave cavity (Figure 9c).…”

Efficient Electrocatalytic Switching of Azoheteroarenes in the Condensed Phases

“…Upon applying the electric field, the ions migrate to the corresponding electrode, creating surface-charge-dipole (SCD) regions. These SCD regions result in creating ohmic contacts at the ITO/photoswitch interface, improving the charge injection into the material . Such behavior results in a greater number of charges being injected into 3 (51.0 mC over 5 h) than 1 (3.09 mC over 5 h) and therefore a greater degree of redox-induced switching.…”

“…These SCD regions result in creating ohmic contacts at the ITO/photoswitch interface, improving the charge injection into the material. 44 Such behavior results in a greater number of charges being injected into 3 (51.0 mC over 5 h) than 1 (3.09 mC over 5 h) and therefore a greater degree of redox-induced switching. Thus, the combination of the stable ionic liquid phase of compound 3, in both E and Z forms, and the absence of unfavorable crystallization, which increases the resistance across the film, are attributed to the high completeness of switching in the condensed phase.…”

Advances in Emerging Photonic Memristive and Memristive‐Like Devices

“…As the prevalent material, polymers have been widely applied in various devices owing to their high feasibility, low toxicity, and flexibility. [ 254 , 255 , 256 ] Regarding the memristor, the polymers can be acted as a blocking layer and floating layer, contributing to the resistive switching behaviors. [ 257 , 258 ] However, given the low light absorption and light insensitivity, few reports mention the application of polymer in photonic memristive devices.…”

“…[ 260 , 261 ] However, the applications of the traditional electronic memristive devices have been impeded due to the single function, weak expansibility, device vulnerability, and narrow bandwidth. [ 248 , 249 , 250 , 251 , 252 , 253 , 254 , 255 , 256 , 257 , 258 , 259 , 260 , 261 , 262 , 263 ] In order to satisfy various kinds of applications, the research of novel memristive devices is imminent. Recently, with the merits of non‐contact operation, non‐destructive properties, and low power consumption, photonic memristive devices have attracted great attention, which enables them to better realize the function of traditional electrically controlled memristive devices.…”