Topochemical Polymerization of C 70 Controlled by Monomer Crystal Packing

Abstract

Polymeric forms of C 60 are now well known, but numerous attempts to obtain C 70 in a polymeric state have yielded only dimers. Polymeric C 70 has now been synthesized by treatment of hexagonally packed C 70 single crystals under moderate hydrostatic pressure (2 gigapascals) at elevated temperature (300°C), which confirms predictions from our modeling of polymeric structures of C 70 . Single-crystal x-ray diffraction shows that the molecules are bridged into polymeric zigzag chains that extend along the c axis of the parent structure. Solid-state nuclear magnetic resonance and Raman data provide evidence for covalent chemical bonding between the C 70 cages.