First Molecular Superconductor with the Tris(Oxalato)Aluminate Anion, β″-(BEDT-TTF)4(H3O)Al(C2O4)3·C6H5Br, and Isostructural Tris(Oxalato)Cobaltate and Tris(Oxalato)Ruthenate Radical Cation Salts

Abstract

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.

Superconductivity and Charge Ordering in BEDT-TTF Based Organic Conductors with β″-Type Molecular Arrangement

“…β -(BEDT-TTF) 4 [(H 3 O)Ga(C 2 O 4 ) 3 ]PhNO 2 , which we focus on in this review, belongs to the 4:1 β -type BEDT-TTF-tris(oxalato)metallate salts known as the Day series [24,25]. This 4:1 β -type family, having the formula (BEDT-TTF) 4 AM(C 2 O 4 ) 3 G, is synthesized by means of electrochemical oxidation of the organic BEDT-TTF donor with 18-crown-6 ether and counter molecule AM(C 2 O 4 ) 3 in solvents G under galvanostatic current.…”

“…Martin and co-workers successfully obtained pseudo-κ [26][27][28], α-β [26,29], and 2:1-β with 18-crown-6 [26,[30][31][32] phases in addition to the 4:1 β -phase by optimizing the synthesis conditions for each phase. For the 4:1 β -phase, independent studies by Akutsu, Coronado, Martin, and Prokhorova and their co-workers report an extensive variety of M(=Fe 3+ , Cr 3+ , Ga 3+ , Rh 3+ , Ir 3+ , Ru 3+ , Al 3+ , Co 3+ ) and G(=C 5 H 5 N, DMF, PhCN, PhNO 2 , PhBr, PhCl, PhF, PhI, CH 2 Cl 2 ) [23,[25][26][27][28][33][34][35][36][37][38]. When M = Ga and G = PhNO 2 , the 4:1 β -salt is often obtained as the minor product with the major product of the semiconducting pseudo-κ phase crystals.…”

Perspectives on Molecular Materials—A Tribute to Professor Peter Day

“…The contribution by L. Martin et al at Nottingham Trent University (UK), H. Akutsu et al at Osaka University (Japan) and S. Imajo at the University of Tokyo (Japan), ref. [15], reports the synthesis, crystal structure and conducting properties of two new members of the Peter Day series, reported in 1995. These new salts are: the first superconductor with the diamagnetic tris(oxalato)aluminate anion (with a T c of ≈ 2.5 K) and the first example of a β" phase with the tris(oxalato)cobaltate anion.…”

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

“…Taking β′′-(BEDT-TTF) 4 [(H 3 O)Fe(C 2 O 4 ) 3 ]·benzonitrile as the starting point and changing the counter cation (H 3 O + , K + , NH 4 + ) 8,9 or changing the metal centre of the Fe(C 2 O 4 ) 3 3− anion has only small effect upon the donor packing and the conductivity. Changing the metal ion to Al 3+ , 10 Co 3+ , 10 Cr 3+ , 11 Ga 3+ , 12 Mn 3+ , 13 Rh 3+ , 14 or Ru 3+ , 10,15 does however change the magnetic moments in the anion layer. A much more pronounced effect upon the conducting properties results from changing the guest molecule within the anion layer hexagonal cavity.…”

“…3− anion has only small effect upon the donor packing and the conductivity. Changing the metal ion to Al 3+ , 10 Co 3+ , 10 Cr 3+ , 11 Ga 3+ , 12 Mn 3+ , 13 Rh 3+ , 14 or Ru 3+ , 10,15 does however change the magnetic moments in the anion layer. A much more pronounced effect upon the conducting properties results from changing the guest molecule within the anion layer hexagonal cavity.…”