Spin crossover and high spin filtering behavior in Co-Pyridine and Co-Pyrimidine molecules

Abstract

We present a theoretical study on a series of cobalt complexes, which are constructed with cobalt atoms and pyridine/pyrimidine rings, using density functional theory. We investigate the structural and electric transport properties of spin crossover (SCO) Co complex with two spin states, namely low-spin configuration [LS] and high-spin configuration [HS]. Energy analyses of the two spin states imply that the SCO Co-Pyridine and Co-Pyrimidine complexes may display a spin transition process accompanied by a geometric modification driven by external stimuli. A nearly perfect spin filtering effect is observed in the Co-Pyrimidine complex with [HS] state. In addition, we also discover the contact-dependent transmission properties of Co-Pyridine. These findings indicate that SCO Co complexes are promising materials for molecular spintronic devices.

Enhancing Spin-Transport Characteristics, Spin-Filtering Efficiency, and Negative Differential Resistance in Exchange-Coupled Dinuclear Co(II) Complexes for Molecular Spintronics Applications

“…Further, Ruiz and co-workers have reported a Fe II SCO complex, trans -[Fe­(tzpy) 2 (NCS) 2 ] (tzpy = 3-(2-pyridyl)­[1,2,3]­triazolo­[1,5- a ]­pyridine, NCS = isothiocyanato), with the SFE of 100% and a dominating β-current carrier . Other than Fe II complexes, Co II mononuclear complexes were also reported to exhibit SCO phenomena between a low-spin (ls) t 2g 6 e g (S = 1/2) to high-spin (hs) t 2g 5 e g 2 (S = 3/2) and have been reported to yield superior SFE s. − Despite Fe II /Co II systems being robust toward SCO properties, retaining the SCO characteristics at the interface is often challenging as the nature of the metal–ligand interaction, which is very delicate for the observation of SCO often altered at the interface. An alternative approach to such SCO systems has been explored with the [Co 2 (L)­(hfac) 4 ] ( 1 ) (here L = 5,5′-di­(4′′,4′′′-di-S,S′-thiophenylethynyl)-2,2′-bipyrimidine and hfac = hexafluoroacetylacetonato) complex.…”

Monitoring the Substrate‐Induced Spin‐State Distribution in a Cobalt(II)‐Salen Complex by EPR and DFT

“…Despite the growing interest in Co(II) based SCO systems, the literature remains dominated by Fe‐based counterparts [23,24] . Nevertheless Co(II)‐salen type complexes (bearing an N 2 O 2 ligand backbone) remain interesting systems to investigate, particularly as the SCO response can be induced by weak axial coordination of organic bases such as pyridine [25–31] . In some cases, variations to the Salen ligand framework in these Co(II) complexes have also been observed to undergo thermally induced SCO in the solid‐state [32–34] .…”

“…[23,24] Nevertheless Co(II)-salen type complexes (bearing an N 2 O 2 ligand backbone) remain interesting systems to investigate, particularly as the SCO response can be induced by weak axial coordination of organic bases such as pyridine. [25][26][27][28][29][30][31] In some cases, variations to the Salen ligand framework in these Co(II) complexes have also been observed to undergo thermally induced SCO in the solid-state. [32][33][34] On the other hand, substrate mediated SCO is arguably less well studied for such Co(II) systems.…”

Multilevel Resistance Switching and Enhanced Spin Transition Temperature in Single- and Double-Molecule Spin Crossover Nanogap Devices

“…In this study we use the electromigration method, [12][13][14] which has the advantage of scalability and a rigid silicon wafer substrate for better device stability. This is particularly important in the case of magnetic electrodes, 15 where SCO compounds have the potential to be used as highly efficient spin-filters, [16][17][18] as it can eliminate effects from magnetostriction. 19 DFT modelling of isolated SCO compounds in contact with metallic electrodes predicts that in general there will be a change in conductance associated with the spin transition.…”

“…In this study, we use the electromigration method, − which has the advantages of scalability and a rigid silicon wafer substrate for better device stability. This is particularly important in the case of magnetic electrodes, where SCO compounds have the potential to be used as highly efficient spin filters, − as they can eliminate magnetostriction effects …”