Magnetism of Molecular Conductors

Abstract

The study of the magnetic properties of molecular conductors has experienced, during the last decades, a very significant evolution, comprising systems of increasing molecular complexity and moving towards multifunctional materials, namely by their incorporation in conducting networks of different paramagnetic centers. In this context, molecular magnetic conductors have emerged at the intersection between the fields of molecule-based conductors and molecule-based magnets as a very exciting class of multifunctional materials in which the interaction and synergy between conduction electrons and localized magnetic moments can lead to new phenomena, complex phase diagrams, and different ground states, with a large potential for technological applications, namely in electronic devices, sensors and in spintronics. Among these phenomena are unusual field-induced transitions, including magnetic field-induced superconductivity, very large magnetoresistance effects, conductors that are switchable by magnetic field, changes of magnetic ordering or spin state, etc.This Special Issue of Magnetochemistry features a collection of research contributions illustrating recent achievements in different aspects of this topic concerning the development, study and understanding of the magnetic properties of molecular conductors and their applications. Quite different types of compounds are considered.A contribution by Tamotsu Inabe et al.[1], reviews a series of compounds based on axially ligated phthalocyanines. Metal phthalocyanines are one of the first examples of compounds where, in addition to delocalized π-conduction electrons in the ligand, there can also be localized magnetic moments for some metals. The π-d interaction of these local moments embedded in the sea of conduction electrons has long since been identified as a source of possible interesting phenomena. In this contribution, the properties of TPP[M(Pc)(CN) 2 ] 2 compounds (TPP = tetraphenylphosphonium, Pc = phthalocyaninato), with M = Fe and Cr are reviewed, emphasizing carrier localization and charge disproportionation enhanced by the interaction between local magnetic moments and conduction π-electrons (π-d interaction), and the large negative magnetoresistance, reflecting the difference in the anisotropy of different d-d, π-d, and π-π interactions.Two other contributions in this issue concern a family of compounds with two types of chains (conducting and magnetic), based on the organic perylene donor and inorganic [M(mnt) 2 ] anions, which have been studied for more than 30 years, but are still unique among molecular materials. In a review by Jean-Paul Pouget et al. [2], the structural instabilities exhibited of these salts are reviewed and discussed in relation to the magnetic properties of the 1D spin-Peierls (SP) instability of the dithiolate stacks, showing, in particular, that α-(Per) 2 [M(mnt) 2 ] salts exhibit the physical properties expected of a two-chain Kondo lattice. In another contribution by Manuel Matos et al. [3], these compounds are also addressed, ...

Magnetic Molecular Conductors Based on Bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) and the Tris(chlorocyananilato)ferrate(III) Complex

“…Magnetic molecular conductors are a challenging class of multifunctional materials of special interest in contemporary material science, since coexistence or even interplay between delocalized π-electrons and localized d-electrons can lead to unusual and peculiar phenomena such as magnetic field-induced superconductors, magnetoresistance effects, magnetic field-switchable conductors, etc., with technological applications in molecular electronics and spintronics . Molecular π–d systems exhibit a variety of types of electron transport (conducting, semiconducting, and insulating), which can be finely tuned by the π–d interactions and, therefore, by a wise choice of both the organic donor, carrier of conductivity, and magnetic counterions, carriers of magnetic properties (ferro-, ferri-, anti-ferromagnetism).…”