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Peter Day’s research group reported the first molecular superconductor containing paramagnetic metal ions in 1995, β″-(BEDT-TTF)4(H3O)Fe(C2O4)3·C6H5CN. Subsequent research has produced a multitude of BEDT-TTF-tris(oxalato)metallate salts with a variety of structures and properties, including 32 superconductors to date. We present here the synthesis, crystal structure, and conducting properties of the newest additions to the Day series including the first superconductor incorporating the diamagnetic tris(oxalato)aluminate anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, which has a superconducting Tc of ~2.5 K. β″-(BEDT-TTF)4(H3O)Co(C2O4)3·C6H5Br represents the first example of a β″ phase for the tris(oxalato)cobaltate anion, but this salt does not show superconductivity. [ABSTRACT FROM AUTHOR]

Peter Day’s research group reported the first molecular superconductor containing paramagnetic metal ions in 1995, β″-(BEDT-TTF)4(H3O)Fe(C2O4)3·C6H5CN. Subsequent research has produced a multitude of BEDT-TTF-tris(oxalato)metallate salts with a variety of structures and properties, including 32 superconductors to date. We present here the synthesis, crystal structure, and conducting properties of the newest additions to the Day series including the first superconductor incorporating the diamagnetic tris(oxalato)aluminate anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, which has a superconducting Tc of ~2.5 K. β″-(BEDT-TTF)4(H3O)Co(C2O4)3·C6H5Br represents the first example of a β″ phase for the tris(oxalato)cobaltate anion, but this salt does not show superconductivity.

Graphical abstract Highlights • Multifunctional molecular conductors of BEDT-TTF with tris(oxalato)metallate. • 2017 discovery of molecular superconductor β″-(BEDT-TTF) 2 [(H 2 O)(NH 4) 2 M(C 2 O 4) 3 ]·18-crown-6. • Kosterlitz-Thouless transition in 2D superconductor. • Chiral induction in molecular semiconductors. • Combination of ferromagnetism and metallic behaviour. Abstract This review presents the synthesis, crystal structures and conducting properties of BEDT-TTF radical-cation salts with the tris(oxalato)metallate anion [BEDT-TTF = bis(ethylenedithio)tetrathiafulvalene]. This series has received much attention owing to the wide variety of conducting properties that have been observed. As well as including numerous metals, semiconductors and insulators, there are over twenty superconductors in this series. The series also includes several examples of multifunctionality where it has been possible to combine together particular physical properties in the same lattice such as electrical conductivity with magnetism, chirality or proton conductivity. This review presents an overview of the flexibility of the coordination chemistry of the oxalate ligand and the variety of packing arrangements of the tris(oxalato)metallate complexes in the insulating layers of these radical-cation salts. [ABSTRACT FROM AUTHOR]