In Search of Chiral Molecular Superconductors: κ‐[(S,S)‐DM‐BEDT‐TTF]₂ClO₄ Revisited

Abstract

The relationship between chirality and superconductivity is an intriguing question. The two enantiomeric crystalline radical cation salts κ‐[(S,S)‐DM‐BEDT‐TTF]2ClO4 and κ‐[(R,R)‐DM‐BEDT‐TTF]2ClO4, showing κ‐type arrangement of the organic layers, are investigated in search for superconducting chiral molecular materials following a 1992 report indicating the occurrence of a superconducting transition in the former compound. While the initial interpretation is presently challenged through in‐depth temperature and pressure dependent single crystal resistivity measurements combined with band structure calculations, the two chiral conductors show metal like behavior with room temperature conductivities of 10–30 S cm−1 at ambient pressure and stabilization of the metallic state down to the lowest temperatures under moderate pressures. Moreover, their structural and theoretical investigations reveal an original feature, namely the existence of two different κ layers with 1D and 2D electronic dimensionality, respectively, as a consequence of an interlayer charge transfer. The resistivity drop observed for one sample below 1 K and insensitive to magnetic field, possibly results from mixing in‐plane and out‐of‐plane contributions to the measured resistance and suggests current induced charge order melting. This feature contradicts the occurrence of superconductivity in these chiral molecular conductors and leaves open the discovery of the first chiral molecular superconductors.

Conducting chiral nickel(ii) bis(dithiolene) complexes: structural and electron transport modulation with the charge and the number of stereogenic centres

“…34,35,36 Moreover, no systematic study on the influence of the number of stereogenic centres on the conducting properties of anionic and neutral metal bis(dithiolene) complexes has been performed to date. Since the presence of dimethylethylenedithio (dm-edt) or methyl-ethylenedithio (me-edt) units in the structure of chiral TTF precursors such as DM-EDT-TTF, 27,32,37 DM-BEDT-TTF, 38 or Me-EDT-TTF 39 proved to be beneficial for the observation of a rich variety of structural variations and conducting properties, we decided to investigate the introduction of one or two methyl substituents on the dddt ligand in the corresponding chiral anionic and neutral Ni(dithiolene)2 complexes (Scheme 1), following our previous report dealing with the synthesis and properties of enantiopure (NBu4)[M(dm-dddt)2] and [M(dm-dddt)2] (M = Ni, Au) complexes. 40 While only the conducting properties of the (NBu4)[Ni(dm-dddt)2] salts have been previously investigated at ambient pressure, we present herein an in-depth study on the modulation of the crystal structures and transport properties under high pressure with the charge and number of stereogenic centres in the anionic and neutral nickel-bis(dithiolene) complexes containing the dm-dddt and me-dddt ligands, together with extended Hückel and DFT band structure calculations.…”

Enhanced Photocatalytic Hydrogen Production Activity by Constructing a Robust Organic-Inorganic Hybrid Material Based Fulvalene and TiO2

“…Tetrathiafulvalene (TTF) and its derivatives own unique electron-rich and redox-active properties [ 28 ], which commonly work as functional building blocks to construct two-dimensional (2D) and three-dimensional (3D) framework materials (COF or MOF) and organic-inorganic hybrid materials, and have been intensively studied in the fields of photothermal conversion, photocatalysis [ 29 , 30 , 31 , 32 ], superconductors [ 33 ], sensors [ 34 , 35 , 36 ] and solar cell [ 37 , 38 , 39 ]. For example, Zhou et al reported a composite (Ag@Dy-m-TTFTB) containing Ag nanoparticles and tetrathiafulvalene-based MOFs materials with a wide absorption wavelengths range (200–1000 nm) and efficient NIR photothermal conversion owing to the doping of the partially oxidized TTF ligands (TTF •+ ) and the plasmonic Ag nanoparticles [ 40 ].…”

Unusual stoichiometry, band structure and band filling in conducting enantiopure radical cation salts of TM-BEDT-TTF showing helical packing of the donors

“…Indeed, while occurrence of a superconducting transition was claimed for the enantiopure phase k-[(S,S)-DM-BEDT-TTF] 2 ClO 4 , 13 based on the dimethyl-BEDT-TTF (DM-BEDT-TTF) donor, our recent investigations on both enantiomers of this chiral material ruled out this initial assumption. 14 Whereas several methyl substituted chiral BEDT-TTF and EDT-TTF derivatives, such as DM-BEDT-TTF, [13][14][15][16] DM-EDT-TTF, [8][9][10]17 DM-EDT-TTF diamides, 18 or Me-EDT-TTF, 19,20 provided interesting conducting materials, TM-BEDT-TTF still remains the flagship donor of this family of chiral precursors when considering the number of reported radical cation salts based on the enantiomers of TM-BEDT-TTF and various anions of different shapes, charge and magnetic properties. Indeed, several crystalline salts formulated as (TM-BEDT-TTF) 2 XF 6 (X = P, As, Sb), 21 (TM-BEDT-TTF)I 3 , 22 (TM-BEDT-TTF) 3 (XO 4 ) 2 (X = Cl, Re), 23 (TM-BEDT-TTF) x [MnCr(ox) 3 ] (ox = oxalate), 24 (TM-BEDT-TTF)[(rac)-TRISPHAT], 25 (TM-BEDT-TTF) 3 (PPh 4 )[KFe(Cl 2 An) 3 ] (Cl 2 An = dichloroanilate), 26 or (TM-BEDT-TTF) 2 (Re 6 S 6 Cl 8 ), 27 obtained by electrocrystallization and showing semiconducting or metallic behaviour, have been described over the years since the initial report on TM-BEDT-TTF.…”