Studies of intermolecular interactions in transition metal complexes—VI[1]: The electrical properties of some quasi-one dimensional mixed valence complexes at ultra-high pressures

Abstract

Electrical conductivity and conductivity activation energy measurements were carried out on the quasi-one dimensional (1-D) mixed valence complexes, Pd(NH 3) 2Br 3 and Au(DBS)X 2 (DBS = dibenzylsulfide, X = Cl, Br), at pressures up to 360 Kbar using a diamond compact-tipped Drickamer apparatus. The results indicate an enormous enhancement of the conductivity with values approaching 5 Ω −1 cm −1 for the palladium complex and 2 × 10 −3 Ω −1 cm −1 for Au(DBS)Br 2 in the range 100–250 Kbar pressure. The increase in conductivity and decrease in the activation energy is attributed to compression along the 1-D chains, leading to more nearly equivalent coordination environments for the intrachain metal atoms. A maximum in the conductivity and a minimum in the activation energy is observed for these complexes, indicating that the pressure induced reduction in metal site inequivalency reaches a limit and that conversion to the hypothetical uniform-valence (Pd(III) or Au(II)), 1-D metallic state is not attained at high pressures. These observations are discussed in the context of the interatomic distances changes anticipated at high pressure.