The Peter Day Series of Magnetic (Super)Conductors

Abstract

Here, we review the different series of (super)conducting and magnetic radical salts prepared with organic donors of the tetrathiafulvalene (TTF) family and oxalato-based metal complexes (ox = oxalate = C2O42−). Although most of these radical salts have been prepared with the donor bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF = ET), we also include all the salts prepared with other TTF-type donors such as tetrathiafulvalene (TTF), tetramethyl-tetrathiafulvalene (TM-TTF), bis(ethylenediseleno)tetrathiafulvalene (BEST), bis(ethylenedithio)tetraselenafulvalene (BETS) and 4,5bis((2S)-2-hydroxypropylthio)-4’,5’-(ethylenedithio)tetrathiafulvalene (DMPET). Most of the oxalate-based complexes are monomers of the type [MIII(C2O4)3]3−, [Ge(C2O4)3]2− or [Cu(C2O4)2]2−, but we also include the reported salts with [Fe2(C2O4)5]4− dimers, [MII(H2O)2[MIII(C2O4)3]2]4− trimers and homo- or heterometallic extended 2D layers such as [MIIMIII(C2O4)3]− and [MII2(C2O4)3]2−. We will present the different structural families and their magnetic properties (such as diamagnetism, paramagnetism, antiferromagnetism, ferromagnetism and even long-range magnetic ordering) that coexist with interesting electrical properties (such as semiconductivity, metallic conductivity and even superconductivity). We will focus on the electrical and magnetic properties of the so-called Day series formulated as β”-(BEDT-TTF)4[A+MIII(C2O4)3]·G, which represents the largest family of paramagnetic metals and superconductors reported to date, with more than fifty reported examples.

Introduction of new guest molecules into BEDT-TTF radical-cation salts with tris(oxalato)ferrate

“…However, the b axis length is shorter 3) Å (at 100 K), respectively. 9 Fig. 4 shows the electrical resistance measurements for β″-…”

Enantiopure and racemic radical-cation salts of B(mandelate)2− and B(2-chloromandelate)2− anions with BEDT-TTF

“…24 Prior to this chiral radical-cation salts had only been synthesised from enantiopure anions, 16,17 or from racemates which have been resolved by using chiral solvents for crystal growth. 22…”

“…The most widely reported family of chiral anions with BEDT-TTF salts is that of the tris(oxalato)metallates which have provided a wide array of materials combining magnetism and conductivity in the same material. 22 These compounds contain a mixture of the Δ and Λ isomers of [M(oxalate) 3 ] 3− resulting in a racemic solid-state lattice and the spatial distribution of these layers determines the crystal packing arrangement and ergo the conducting properties. 23…”

Strategies to Improve Electrical Conductivity in Metal–Organic Frameworks: A Comparative Study

“…Different types of electroactive molecules and molecular entities, including tetrathiafulvalene, TCNQ (7,7,8,8-tetracyanoquinodimethane), iodine, NiCB, methyl viologen, etc., have been encapsulated within the channels of MOFs to induce/enhance the electrical conductivity of the parent MOFs. − …”