Rashid, Samina; (2002) Synthesis, structure and properties of BEDT-TTF charge transfer salts. Doctoral thesis (Ph.D), UCL (University College London).

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Abstract

Charge transfer salts based on BEDT-TTF have been the source of many organic superconductors. Research up till now has resulted in the highest Tc (superconducting transition temperature) at 13.5 K. In conjunction with efforts to increase Tc's, the idea of multi-property compounds has also developed. The superconducting state is destroyed by magnetic fields (either external or local internal) because they disrupt the charge carriers (Cooper pairs). However, the first molecular superconductor containing paramagnetic anions was synthesised in 1995, and sparked off the development of compounds exhibiting conducting, optical, or magnetic properties in the same crystal lattice. BEDT-TTF charge transfer salts are promising candidates for multi-property compounds because they consist of segregated layers. The organic layer exhibits conducting properties and different inorganic layers can be chosen or chemically engineered to exhibit varying magnetic properties. This thesis reports the synthesis, crystal structures, and physical properties of several BEDT-TTF salts of the layered compounds with general formula β"-(BEDT-TTF)4[A.M(C 2O4)3].S, where A = H3O+, NH4 +, K+ and M = Fe3+, Cr3+, exhibiting both superconducting and magnetic properties and S = C6H5NO2, H2O.CH 2Cl2. Some unanticipated results are reported; the synthesis and crystal structure of the first BEDT-TTF salt containing a crown ether ion channel, (BEDT-TTF)4[Cr(C2O4)3] 2·C12O6H24·9HxO (where x = 2, 3). Also reported are the synthesis, crystal structure and physical properties of a new hydrated BEDT-TTF chloride, (BEDT-TTF)6Cl 5·4H2O, existing members of this family were last reported in 1995. The first BEDT-TTF charge transfer salt containing an iron oxalate bridged dimer, (BEDT-TTF)4·[Fe 2(C2O4)5], has been synthesised and characterised and has a chequer board structure in contrast to the layered structures. Physical characterisation was by means of transport measurements, magnetic susceptibility measurements, Raman and EPR spectroscopy, and polarised infrared reflectivity.

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