Redox Non‐Innocence of Coordinated 2‐(Arylazo) Pyridines in Iridium Complexes: Characterization of Redox Series and an Insight into Voltage‐Induced Current Characteristics

Abstract

Two examples of a rare class of di-radical azo-anion complexes of 2-(arylazo) pyridine with Ir(III) carrier are introduced. Their electronic structures have been elucidated using a host of physical methods that include X-ray crystallography, cyclic voltammetry, electron paramagnetic resonance spectroscopy, and density functional theory. Room temperature magnetic moments of these are consistent with two nearly non-interacting azo-anion radicals. These displayed rich electrochemical properties consisting of six numbers of reversible and successive one electron CV-waves. Redox processes occur entirely at the coordinated ligands without affecting metal redox state. Apart from reporting their chemical characterization, I-V characteristics of these complexes in film state are investigated using sandwich-type devices comprising of a thin film of 100-125 nm thickness placed between two gold-plated ITO electrodes. These showed memory switching properties covering a useful voltage range with a reasonable ON/OFF ratio and also are suitable for RAM/ROM applications. I-V characteristics of two similar complexes of Rh and Cr with identical ligand environment and electronic structure are also referred for developing an insight into the memory switching ability of Ir- and Rh- complexes on the basis of comparative analysis of responses of the respective systems. In a nutshell, thorough analysis of voltage driven redox dynamics and corresponding solid and solution state current responses of all the systems are attempted and there from an unexplored class of switching devices are systematically introduced.

Synthesis and crystal structure of (1,10-phenanthroline-κ2 N,N′)[2-(1H-pyrazol-1-yl)phenyl-κ2 N 2,C 1]iridium(III) hexafluoridophosphate with an unknown number of solvent molecules

“…In this regard, a variety of cyclometallated iridium complexes have been reported and most of them have potential for the aforementioned applications (Flamigni et al, 2008;Li et al, 2011). The properties of iridium complexes can be tuned by rational design of either the cyclometallating or ancillary ligands (Chen et al, 2010;Goswami et al, 2014;Radwan et al, 2015;Congrave et al, 2017). Among numerous organic conjugate ligands, the cyclometallating ligand 1-phenylpyrazole (ppz) is known for its high triplet energy (Schlegel & Skancke, 1993).…”

Resistance Controllability in Alkynylgold(III) Complex‐Based Resistive Memory for Flash‐Type Storage Applications

“…[19,20] To date, OMDs based on transitionmetal complexes are limited to severalt ypes of transitionmetal complex systems containing nitrogen-donor ligands, for example, silver(I)-tetracyanoquinodimethane (TCNQ), [21] cobalt(II)-L C , [22] bis(2,2'-bipyridyl)(triazolopyridyl)ruthenium(II)c omplexes, [23] lanthanide (Sm 3 + ,E u 3 + ,Gd 3 + )c omplexes, [24] and iridium(III)c omplexes. [25] Research into memory devicesb ased on alkynylgold(III) materials has just begun;h owever,m ost reported devices are only of the writeo nce read many times (WORM) type. [26,27] Conversion of the performance of these devices from WORM-type into flash-type remains challenging.…”

“…By judiciously incorporating coumarin moieties into alkynylgold(III) systems and fine-tuning their electronic properties, the first example of flash-type OMDs based on an alkynylgold(III) complex has been realized. Compared with devices based on complexeso fo ther transition-metal centers, [23,25] devices based on 1 possess stable rewritable behavior under al ower compliance current of 10 À6 A. Moreover,b yp recisely controlling the compliance current, the devices show ad ifferent switching characteristicf rom that of flash-type binary resistance, switching (I cc 10 À3 A) to WORM-type ternary resistance switching (I cc = 10 À2 A). Based on experimental observations and electrical parameter analysis, ap ossible switching mechanism for reliable nonvolatile switching performance has been proposed.…”

Dinuclear Palladium Complexes with Two Ligand‐Centered Radicals and a Single Bridging Ligand: Subtle Tuning of Magnetic Properties

“…[10,11] These speciesa re of interest for applicationsi nt unable electronic switching andm olecular magnetic materials. [12] Modulars ynthesis routes that allow facile installment of different types of bridging ligandsw ould be of interest in order to quickly assess their impact on the magnetic properties of these complexes.…”