CS4C60 - SINGLE-PHASE SYNTHESIS AND ORIENTATIONAL ORDER

Cs4C60 is reported as a pure phase for the first time, using low-tempe rature synthesis. It adopts an orthorhombic distortion of the body-cen tred tetragonal (bct) A(4)C(60) structure found for K4C60 and Rb4C60, due to the orientational ordering of the C-60(4-) anions with the 6:6 bonds directed along the orthorhombic b-axis. The caesium cations occu py two distinct distorted tetrahedral sites, producing the orientation al order to avoid close contact with the five-membered rings of neighb ouring C-60(4-) anions. The structure-directing influence of large cat ions on fulleride structures and the implications for Jahn-Teller dist ortions of the fulleride anions are discussed.