Computational and synthetic approaches to the synthesis of a potential high-temperature organic superconductor precursor: heterofullerene

The first organic superconductor was discovered in 1980. It had a superconducting transition temperature (Tc) of 0.9 K. At the present, the organic superconductor with the highest Tc is a salt of buckminsterfullerene (C60), Cs3C60 (Tc = 38 K at 7.9 kbar pressure). Theoretical studies suggest that superconductors derived from smaller fullerenes with greater curvature possess substantially elevated T c's, perhaps approaching room temperature. Computational methods were used to design small fullerenes and heterofullerenes to test the curvature theory. The th-orbital axis vector (POAV) correlation was employed to assess the kinetic stability of precursor candidates. Over three hundred compounds were subjected to the POAV analysis. A heterofullerene with T d symmetry, C36N4, was selected for synthesis. High temperature (900-1100 °C) synthetic routes to C36N 4 were explored rather than a conventional multistep synthesis, which would be extremely difficult. Syntheses of three thermal precursors were completed. A thermolysis apparatus was constructed to carry out the high temperature reactions. Experimental procedures for using the thermolysis apparatus were worked out by reproducing the known conversion of naphthalene to C60 at 1000 °C. The thermolysis products were analyzed by matrix-assisted laser desorption ionization and time-of-flight mass spectrometry (MALDI-TOFMS). Mass spectra of the thermolysis products of the first precursor examined, 2-methylisoindoline 2-oxide, indicated that C36H22N 4 is a major product. A variety of strategies are conceivable for altering the reaction conditions to obtain C36N4. Two other precursors containing 36 carbon atoms and 4 nitrogen atoms with the appropriate connectivity to form C36N4 failed to give C36N4 but afforded key intermediates along the pathway to C36N4 .