Spin-filter transport and magnetic properties in a binuclear Cu(ii) expanded porphyrin based molecular junction

Although the magnetic and transport properties of molecular junction systems composed of metalled porphyrins or phthalocyanines have been broadly studied in recent years, to date no studies have been devoted to evaluate the aforementioned properties in junction systems featuring metalled expanded porphyrins as active elements. The present work reports a detailed theoretical study of the magnetic and electronic transport properties of the recently synthesized dinuclear Cu(ii)-naphthoisoamethyrin complex (PyCu₂). This is the first work on performing these kinds of studies using a magnetically coupled metallic expanded porphyrin as a molecular kernel. DFT and wave function-based methods have been used to determine the nature of the magnetic interaction between the metallic centres, characterized by the exchange coupling constant J, showing that although this was found to be weakly antiferromagnetic, after an exhaustive analysis it turns out that the coupling has a ferromagnetic nature with a value of J = 14.2 cm^-1. Once the magnetic ground state of PyCu₂ was rigorously established, the spin resolved transport properties of the device composed of the expanded porphyrin attached to two gold nano-wires were studied by means of the combination of DFT and the nonequilibrium Green's function formalism, in order to explore PyCu₂ prospects as a possible spintronic device.

Transport property of ligand-driven light-induced spin-change Fe-based spin crossover complexes

The Fe-based spin-crossover (SCO) complexes, especially the ligand-driven light-induced spin-change (LD-LISC) systems with high spin-transition temperature, are considered as the most promising building blocks for designing molecular spintronic devices due to their bistability between the high-spin (HS) and low-spin (LS) states. Here, we explore the transport properties of Fe(stpy)₄(NCS)₂ LD-LISC SCO complexes with the trans and cis configurations sandwiched between Au electrodes by performing extensive density functional theory calculations combined with the non-equilibrium Green's function method. As for the trans configuration, the current through the molecular junction with the HS state is significantly larger than that of the LS state, which indicates that this Fe-based LD-LISC SCO complex with the trans configuration could act as a molecular switch when the spin transition is triggered by external stimuli. Remarkably, we observe the nearly perfect spin-filtering effect and obvious negative differential resistance feature in the Fe(stpy)₄(NCX)₂ junctions with the trans and cis configurations, which is attributed by the dramatically different electronic structures of two spin channels and the bias-dependent transmission spectra, respectively. These obtained theoretical findings suggest that the examined Fe-based LD-LISC SCO complexes hold great potential in molecular spintronics.

The transport properties of LD-LISC Fe-based SCO complexes with the trans and cis configuration exhibit robust spin-filtering and NDR features, which highlight them for promising applications in molecular devices.