Non-volatile memories will play a decisive role in the next generation of digital technology. Flash memories are currently the key player in the field, yet they fail to meet the commercial demands of scalability and endurance. Resistive memory devices, and in particular memories based on low-cost, solution-processable and chemically tunable organic materials, are promising alternatives explored by the industry. However, to date, they have been lacking the performance and mechanistic understanding required for commercial translation. Here we report a resistive memory device based on a spin-coated active layer of a transition-metal complex, which shows high reproducibility (∼350 devices), fast switching (≤30 ns), excellent endurance (∼10 cycles), stability (>10 s) and scalability (down to ∼60 nm). In situ Raman and ultraviolet-visible spectroscopy alongside spectroelectrochemistry and quantum chemical calculations demonstrate that the redox state of the ligands determines the switching states of the device whereas the counterions control the hysteresis. This insight may accelerate the technological deployment of organic resistive memories.

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Die beiden Isomeren des Titelkations, das trans‐cis‐Derivat (I) und das cis‐cis‐Derivat (III) reagieren mit symm. und unsymm. zweizähnigen Liganden zu den Tris‐Chelaten (II) bzw. (IV).

Design of an efficient new catalyst that can mimic the enzymatic pathway for catalytic dehydrogenation of liquid fuels like alcohols is described in this report. The catalyst is a nickel(II) complex of 2,6-bis(phenylazo)pyridine ligand (L), which possesses the above requisite with excellent catalytic efficiencies for controlled dehydrogenation of alcohols using ligand-based redox couple. Mechanistic studies supported by density functional theory calculations revealed that the catalytic cycle involves hydrogen atom transfer via quantum mechanical tunneling with significant k/k isotope effect of 12.2 ± 0.1 at 300 K. A hydrogenated intermediate compound, [NiCl(HL)], is isolated and characterized. The results are promising in the context of design of cheap and efficient earth-abundant metal catalyst for alcohol oxidation and hydrogen storage.

Recent advancement on the redox properties of a selection of transition metal complexes of the azoaromatic ligands: bidentate L(1) [2-(arylazo)pyridine] and tridentate HL(2) [2-(aminoarylphenylazo)pyridine] are described and compared. Due to the presence of a low lying azo-centered π*-orbital, these azoaromatic ligands may exist in multiple valent states. The coordination chemistry of the L(1) ligands was thoroughly studied during the 1980s. These complexes undergo facile reduction in solution at low accessible potentials. One electron reduced azo-complexes, though known for a long time to occur in solution, have only recently been isolated in a crystalline state. New synthetic protocols for the synthesis of metal-bound azo-radical complexes have been developed. Low-valent metal complexes such as metal carbonyls have been found to be excellent starting materials for this purpose. In a few selected cases, syntheses of these complexes were also achieved from very high valent metal oxides using triphenylphosphine as both a reducing and oxo-abstracting agent. Issues related to the ambiguities of the electronic structures in the azo-metal complexes have been discussed considering bond parameters, redox and spectral properties. Unusual redox events such as RIET (Redox-Induced Electron Transfer) phenomena in a few systems have been elaborated and compared with the known example. Novel examples of N=N bond cleavage reactions via four-electron reduction and subsequent C-N bond formation in metal-bound coordinated ligands have been noted.