Abstract
New crystals (1–4) of organic conductors based on the radical cation salts of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with paramagnetic and diamagnetic tris(oxalato)metallate anions {A+[M3+(ox)3]3−G}2−, where M is Cr, Ga; G is 2-chloropyridine, 2-bromopyridine; and A+ is [K0.8(H3O)0.2]+ have been prepared and their crystal structure and transport properties were studied. All crystals belong to the monoclinic group of the (BEDT-TTF)4A+[M3+(ox)3]G family with β″-packing type of conducting BEDT-TTF layers. In contrast to the known superconducting crystals with M3+ = Fe3+ and G = 2-chloro- or 2-bromopyridine (Tc = 4.0–4.3 K), crystals with Cr3+ and Ga3+ ions exhibit metallic properties down to 0.5 K without superconducting transition. Upon cooling these crystals, the incommensurate superstructure appears, which has never been observed before in the numerous β″-salts of the family. In addition, orthorhombic (sp. group Pbca) semiconducting crystals α″-(BEDT-TTF)5[Ga(ox)3]·3.4·H2O·0.6 EtOH (5) were obtained. It is a new compound in the family of BEDT-TTF crystals with tris(oxalato)metallate anions.
Highlights
IntroductionThe great family of layered molecular conductors and superconductors based on radical cation salts of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with supramolecular tris(oxalato)metallate anions includes compounds having a different stoichiometry, crystal structure, and various physical properties [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33]
We have shown that the use of 2-ClPy as a guest solvents and [Ga(ox)3 ]3− as a counterion leads to the formation of both β”-(BEDT-TTF)4 [K0.8 (H3 O)0.2 ][Ga(ox)3 ]·2-ClPy (3) and α”-(BEDT-TTF)5 [Ga(ox)3 ]·3.4·H2 O·0.6
These structural transitions arise from noticeable positional shifts of all components of the complex anion, giving rise to two nonequivalent organic β” layers and the partial ordering of the ethylene groups of BEDT-TTF molecules
Summary
The great family of layered molecular conductors and superconductors based on radical cation salts of the bis(ethylenedithio)tetrathiafulvalene (BEDT-TTF) with supramolecular tris(oxalato)metallate anions includes compounds having a different stoichiometry, crystal structure, and various physical properties [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33]. The salt with the formula [BEDT-TTF]3 [M2+ M3+ (ox)3 ], where M2+ is Mn2+ and M3+ is Cr3+ (3:1 salt), combine metallic conductivity and ferromagnetism in the same lattice [28]. The largest group of salts comprises paramagnetic (super)conductors (BEDT-TTF) A+ [M3+ (ox)3 ]G (4:1 salts), where A+ = K+ , NH4+ , Rb+ , H3 O+ , and M = Fe, Cr, Mn, Ru, Rh, Ga, Al, Co; and G is a neutral ‘guest’ solvent molecule [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27]. The 4:1 crystals possess a great diversity of structural and conducting
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