A Two-Dimensional Organic Metal Based on Fullerene (original) (raw)

2010, Angewandte Chemie International Edition

We report the synthesis and studies of the physical properties of the first two-dimensional (2D) fullerene organic metal to have 2D layers with a honeycomb arrangement of C 60 C À , (MDABCO + )·TPC·(C 60 C À ) (1); we employed a multicomponent and molecular symmetry synthetic approach, starting from the N-methyldiazabicyclooctane cation (MDABCO + ) and triptycene (TPC). Compound 1 is a fascinating example of a material composed of only light elements (C, H, N) that exhibits a metallic state down to 1.9 K. Salts of fullerene C 60 with a number of different inorganic cations have previously shown metallic or superconducting properties. Among the fullerene metals, the best known families are MC 60 salts (M = K, Rb, Cs), which contain linearly polymerized C 60 C À , and superconducting M 3 C 60 salts (M = alkali metals), obtained by doping C 60 with alkali metals, which have transition temperatures (T c ) of up to 38 K. [2] As metal cations expand the three-dimensional (3D) lattice of the initial C 60 framework, M 3 C 60 salts exhibit 3D metallic conductivity, whereas MC 60 salts are either 3D (when M = K) or quasi-1D metals (when M = Rb or Cs). 2D fullerene metals have not yet been obtained, whilst the various possible ways of modifying M x C 60 salts have almost been exhausted. The idea of obtaining purely organic molecular metals or superconductors from fullerenes has remained unrealized, despite being considered for many years. None of the C 60 C À salts of organic cations have exhibited metallic properties. The salt (NMe 4 + )·(C 60 C À )·THF 1.5 showed rather high conductivity, yet was a semiconductor. By synthesizing organic molecular crystals from C 60 and organic electron donor molecules, it is possible to produce conductors with unique structures and properties.