Novel alloy polymers formed from ortho-carborane and benzene or pyridine

Polymer films have been formed by electron-induced cross-linking of condensed ortho-carborane and benzene (B10C2HX:BNZ) or pyridine (B10C2HX:py) at 110 K, followed by warming up to room temperature. High resolution core-level photoemission and molecular orbital calculations demonstrate that the reaction of the icosahedra with the aromatic group is site-specific: bonding occurs between a C atom on the aromatic group and a B site bound to other boron atoms on the icosahedron. This site specificity determines a systematic variation in the valence band maximum relative to the Fermi level from −4.3 eV for cross-linked ortho-carborane to −2.6 eV for B10C2HX:BNZ and −2.2 eV for B10C2HX:py. The results indicate the ability to form a new class of materials that are a cross between a molecular solid and a network polymer. Further, the electronic properties of these materials can be systematically tuned for a broad variety of applications in neutron detection, nano-electronics and spintronics. (paper)