Topochemical polymerization of C70 controlled by monomer crystal packing.

Polymeric forms of C60 are now well known, but numerous attempts to obtain C70 in a polymeric state have yielded only dimers. Polymeric C70 has now been synthesized by treatment of hexagonally packed C70 single crystals under moderate hydrostatic pressure (2 gigapascals) at elevated temperature (300 degrees C), which confirms predictions from our modeling of polymeric structures of C70. 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 C70 cages.