Structure-property relationships for (beta)- and (kappa)-phase BEDT-TTF salts and their use in the synthesis of (kappa)-(BEDT-TTF)2Cu(N(CN)2)Br. A salt having the highest T(sub c) (inductive onset = 11.6 K, resistive, onset = 12.5 K) yet observed in an organic superconductor

A new ambient pressure organic superconductor, kappa-(BEDT-TTF)2Cu(N(CN)2)Br, was discovered with an inductive onset (Tc) = 11.6 + or - 0.1 K (resistive onset = 12.5 + or - 0.1 K). The anion in the new salt consists of a polymeric mixed halide-pseudohalide cuprate(I) species. Because of the large number of metal/halide/pseudohalide substitutions that can be made in this anionic species, it opens up an entirely new conceptual approach to the design of additional conducting and superconducting (with even higher (Tc)'s) cation-radical salts by use of planar polymeric anions. Studies along these lines are currently under way in the lab. It is also becoming increasingly clear that in terms of structure (both are layered superconductors) and the physics (both are type II-superconductors with anisotropic coherence lengths, anisotropic H(sub c2), and in which superconductivity is competing with magnetic ground states, etc.), the organic superconductors are more similar to the high (Tc) oxide superconductors than to other classes of superconductors. Thus, the prospects for discovering high (Tc) in organic systems appear very bright.