A Singlet-Diradical Co(III)-Dimer as a Nonvolatile Resistive Switching Device: Synthesis, Redox-Induced Interconversion, and Current–Voltage Characteristics

Abstract

Herein we report a ligand-centered redox-controlled strategy for the synthesis of an unusual binuclear diradical cobalt(III) complex, [Co2 III(L•3–)2] (1), featuring two three-electron reduced trianionic monoradical 2,9-bis(phenyldiazo)-1,10-phenanthroline ligands (L •3–) and two intermediate-spin cobalt(III) centers having a Co–Co bond. Controlled ligand-centered oxidation of 1 afforded two mononuclear complexes, [CoII(L •–)(L0)]+ ([3])+ and [CoII(L0)2]2+ ([2]2+), which upon further ligand-centered reduction yielded a di-azo-anion diradical complex, [CoII(L •–)2] (4). In complex 1, two three-electron reduced di-azo-anion monoradical ligands (L •3–) bridge two intermediate Co(III) centers at a distance of 2.387(2) Å, while upon oxidation, one of the coordinating azo-arms of L becomes pendent, and in complexes [2]2+, [3]+, and 4, two tetradentate ligands coordinate a single Co(II) center in a tridentate meridional fashion with one uncoordinated azo-arm from each of the ligands. In the presence of reducing agents, the monomers [2]2+, [3]+, and 4 undergo ligand-centered reduction to form azo-anion radicals, and the otherwise pendent azo-arms in the presence of cobalt(II)-salts like Co(ClO4)2 or CoCl2 bind the second Co(II)-ion; further internal electron transfer from the cobalt center to the arylazo backbone produces the binuclear complex 1. Spectroscopic analysis, DFT studies, and control experiments were performed to understand the electronic structures and the ligand-centered redox-controlled interconversion. The application of complex 1 as a molecular memory device (memristor) was also explored. Complex 1 showed encouraging results as a memristor with a current ON/OFF ratio > 104 and is highly promising for resistive RAM/ROM applications.

Alcohol Dehydrogenation-Triggered Selective C3-Alkylation of Indoles by Homogeneous Azo-aromatic Cobalt Catalysts

“…The peak at energy 779.38 eV corresponds to the Co 2p 3/2 band, and the peak at the energy 795.18 eV corresponds to the band of Co 2p 1/2 (Figure 5B). 62,80 Notably, upon the addition of 1.5 equiv of KO t Bu in a toluene solution of 3, no significant change in the intensity of peaks at 779.38 and 797.18 eV in the XPS spectra was observed. After, addition of another 2 equiv (total 3.5 equiv wrt 3) of KO t Bu, the intensity of the EPR signal of Co(II) (s = 1/2) was found to decrease, and a single-line EPR signal started to appear at g = 2.0031 (Figure 5A).…”

Versatile Titanium Carbide MXene Thin-Film Memristors with Adaptive Learning Behavior

“…11 Certain memristors display only two distinct conducting states and are popularly known as the bistable RS devices, which are useful for data storage, logic operations, and edge computation. 8 Alternatively, the analogue memristors displaying multiple conducting states have the potential to demonstrate functionalities, like in-memory computing, adaptive learning of brain psychology, and neuromorphic computing. Attributing to these shining merits, varieties of smart and advanced materials have been widely explored to design memristors for diverse applications.…”

Solution-Processed Robust Multifunctional Memristor of 2D Layered Material Thin Film

“…Thin film memristors are a fascinating and vital technological development that has garnered significant attention in recent years due to having applications in numerous fields of societal need, including space science, healthcare, artificial intelligence, industry, education, and defense. , A memristor is a passive two-terminal electronic component combining memory and resistor that exhibits an interesting electrical property of resistive switching (RS) from a low-conducting state (LCS) to a high-conducting state (HCS) during recording of current–voltage ( I–V ) characteristics. − Suppose the HCS is retained after removing the bias voltage; in that case, this RS property is termed nonvolatile, which has a great promise to perform data storage and processing simultaneously for in-memory computing. , Accordingly, memristors are useful to overcome the von Neumann bottleneck and memory wall issues of conventional computers. − …”

“…Recently, atomically thick 2D layered van der Waals (vdW) materials have attracted significant interest due to their attractive mechanical, chemical, electronic, and optoelectronic properties. They show promising results for various applications, including thin film transistors, photodetectors, catalysis, sensing, data storage, and neuromorphic computing. ,− Among the entire 2D materials library, MoS 2 is a champion material due to its various functionalities. ,, Hence, the growth of a high-quality MoS 2 thin film is critical to display high performance for sophisticated applications. Accordingly, chemical vapor deposition (CVD) and liquid-phase exfoliation (LPE) are the most common processing techniques to prepare atomically thick 2D MoS 2 sample .…”