Design and Control of Cooperativity in Spin-Crossover in Metal–Organic Complexes: A Theoretical Overview

Abstract

Metal organic complexes consisting of transition metal centers linked by organic ligands, may show bistability which enables the system to be observed in two different electronic states depending on external condition. One of the spectacular examples of molecular bistability is the spin-crossover phenomena. Spin-Crossover (SCO) describes the phenomena in which the transition metal ion in the complex under the influence of external stimuli may show a crossover between a low-spin and high-spin state. For applications in memory devices, it is desirable to make the SCO phenomena cooperative, which may happen with associated hysteresis effect. In this respect, compounds with extended solid state structures containing metal ions connected by organic spacer linkers like linear polymers, coordination network solids are preferred candidates over isolated molecules or molecular assemblies. The microscopic understanding, design and control of mechanism driving cooperativity, however, are challenging. In this review we discuss the recent theoretical progress in this direction.

Isotensional and isometric force-extension response of chains with bistable units and Ising interactions

“…This apparently simple scheme is able to induce very complex behaviors in a large number of physical systems. Without the pretension of being exhaustive, we can cite the snapping and unidirectional waves in elastic metamaterials [3,4], the mechanics of muscle contraction [5,6], the magnetic, optical, and structural bistability in spin-crossover nanocrystals [7,8], the information processing in biochemical reactions [9,10], the protein folding-unfolding processes [11][12][13][14], the DNA overstretching and denaturation [15][16][17][18], and the physics of force-spectroscopy experiments on macromolecules [19][20][21]. This last example is particularly important since force-spectroscopy experiments, conceived to measure the force-extension relation of a single macromolecule, were able for the first time to directly test the thermodynamics and the statistical mechanics of small systems [22,23].…”

Dynamical Properties of Spin‐Crossover Solids Within the Kinetic Spin‐1 BEG Model in the Presence of a Time‐Dependent Magnetic Field

“…The change of induced spin state allows to obtain devices for high density information storage in which the unit of memory can be reduced to a molecule, thus allowing to reach storage capacity more important than those of conventional materials. The thermally induced spin transition leads to both electric and structural changes, often observed as a color and magnetic moment changes . When the interactions between molecules are weak, the HS fraction changes smoothly with the temperature, whereas when it becomes strong, the system exhibits cooperative phenomena, which manifest through the existence of first‐order phase transitions accompanied with thermal hysteresis.…”

Interfacial Spin Manipulation of Nickel-Quinonoid Complex Adsorbed on Co(001) Substrate

“…For spin-crossover complexes, it has been shown that it is possible to switch reversibly between different spin states via an external perturbation such as pressure, temperature, light irradiation, electric or magnetic fields [3,4]. Many magnetic molecules have been synthesized and intensively investigated both theoretically and experimentally in the past years [5][6][7][8]. The progress made recently in the application of spin-crossover complexes in functional devices has been reviewed lately [9,10].…”