Complex formation of ethylenedioxyethylenedithiotetrathiafulvalene (EDOEDT-TTF: EOET) and its self-assembling ability

Abstract

36 kinds of donor(D)–acceptor(A) type charge transfer (CT) solids were prepared based on ethylenedioxyethylenedithiotetrathiafulvalene (EDOEDT-TTF or EOET), which is a hybrid molecule of bis(ethylenedioxy)-TTF (BEDO-TTF or BO) and bis(ethylenedithio)-TTF (BEDT-TTF or ET). A plot of the first CT absorption bands in solids against the difference in first redox potential between donor and acceptor molecules (ΔE) classified the complexes into five groups, A: highly conductive CT complexes with partial CT state and segregated stacks, B: partially ionic CT insulators with alternating stacks, C: essentially neutral clathrate complexes, D: neutral CT insulators with alternating stacks, and E: completely ionic insulators. Group A is spread out over an extensive ΔE range compared to one-dimensional organic metals such as the 1 ∶ 1 TTF–TCNQ system. This indicates that the EOET complexes among this group have a high electronic dimensionality arising from the self-aggregation of the EOET molecules in a fashion similar to the BO ones. However, the self-assembling ability of the EOET molecules is less pronounced than that of the BO ones, thereby giving a metal–insulator transition for many complexes among Group A. The reduced self-assembling ability also affords alternating stacks in (MeO)₂TCNQ, BTDA-TCNQ (Group B) and p-iodanil (Group C) complexes. Two structurally distinct complexes were prepared with spherical C₆₀ (Group D), one containing concave EOET molecules and one-dimensional C₆₀ columns, and the other planar EOET and two-dimensional C₆₀ layers. The F₄TCNQ complex (Group E) exhibits an antiferromagnetic ordering below 7 K, which is intermediate between those in (BO)(F₄TCNQ) (5.4 K) and (ET)(F₄TCNQ) (14 K).