Dodecahedral molecular nitrogen (N20) and related structures

The stability of a dodecahedral cage of nitrogen atoms (N-20, "dodecahedrazane") is examined using semiempirical and density functional theory methods. In agreement with earlier work: it is shown that the nitrogen cage is stable in all vibrational modes. Protonation of the N-20 structure allows hydrogen bonding with another N-20 unit, leading to the possibility of extended structures. Endohedral systems including an enclosed hydrogen atom, hydride ion and hydrogen molecule are all stable. Polymeric systems with covalent bonds can be built by substitution of CH for N and subsequent formation of an N19C-CN19 linkage, and other organic connecting groups (acetylene, ethylene) also form stable structures. The fuel value of N-20 to form dinitrogen is enhanced by recombination of trapped hydrogen in the cage. The decomposition barrier for N-20 is studied along several symmetrical paths, and suggests that these structures may be isolated experimentally. Several possible methods of synthesis are discussed. (C) 1998 Elsevier Science B.V.