Two alternating BEDT-TTF packing motifs in α-κ-(BEDT-TTF)2Hg(SCN)3

Abstract

The first BEDT-TTF charge transfer salt in which alternating electron-donor layers possess α- and κ-type packing motifs has been synthesized. The crystal structure and physical properties of the organic conductor α-κ-(BEDT-TTF)₂Hg(SCN)₃ are described, including a detailed description of its optical properties. The electronic behavior is dominated by a sharp metal-to-insulator transition at T = 176 K which is due to a first-order structural phase transition. The optical properties in the metallic regime are a superposition of those of the α- and κ-phases, while in the insulating state the spectra become more anisotropic in the conducting plane, and the features of the two layers cannot be distinguished.