Synthetic, structural and electronic studies of highly conducting low-dimensional molecular solids

The recent development in the design of organic metals has yielded a number of organic superconductors and other novel materials. The organic salts based on BEDT-TTF (BEDT-TTF or ET = bis(ethylenedithio)-tetrathiafulvalene), have yielded both the largest number of organic superconductors and those with the highest Tc values. A overview of BEDT-TTF salts is presented and a list of cell parameters of BEDT-TTF salts known to date are given. The standard technique employed in synthesizing BEDT-TTF salts, electrocrystallization, is discussed. The discussion includes a description of equipment used in electrocrystallization and a number of factors affecting the crystal growth of BEDT-TTF salts. The crystal structures and conductivities of ten new BEDT-TTF salts have been determined and are described here. One novel solid, {dollar}kappa{dollar}-(ET){dollar}sb2{dollar}Cu{dollar}sb2{dollar}(CN){dollar}sb3,{dollar} contains polymeric two-dimensional network of Cu{dollar}sb2({dollar}CN){dollar}sb3sp{lcub}-1{rcub}{dollar} and {dollar}kappa{dollar}-type packing mode of donor molecules (ET). This salt has very interesting electric properties in that it has a semiconducting-to-metal transition at low temperatures and is superconducting under pressure. The polymorphism of BEDT-TTF salts and a variety of packing modes are fully displayed by these ten structures. A discussion is given of the design of new BEDT-TTF salts and a few factors affecting superconductivity and superconducting transition temperatures. The recent discovery of superconductivity in alkali doped C{dollar}sb{lcub}60{rcub}{dollar} systems supports the optimisim in the search for high Tc superconductors in molecular systems.