Carbon Nanotube Container: Complexes of C50H10 with Small Molecules

The stability of complexes of a recently synthetized (Scott et al. J. Am. Chem. Soc.2011, 134, 107) opened nanocontainer C50H10 with several guest molecules, H2, N2, CO, HCN, H2O, CO2, CS2, H2S, C2H2, NH3, CH4, CH3CN, CH3OH, CH3CCH, 2-butyne, methyl halides, and with noble gas atoms, has been examined by means of symmetry-adapted perturbation theory of intermolecular interactions, which fully incorporates all important energy components, including a difficult dispersion term. All complexes under scrutiny have been found stable for all studied guests at 0 K, but entropic effects cause many of them to dissociate into constituent molecules under standard conditions. The estimation of temperature at which the Gibbs free energy ΔG = 0 revealed that the recently observed (Scott et al. J. Am. Chem. Soc.2011, 134, 107) complex CS2@C50H10 is the most stable at room temperature while the corresponding complexes with HCN and Xe guests should decompose at ca. 310 K and that with CO2 at room temperature (ca. 300 K). In agreement with the ΔG estimation, molecular dynamics simulations performed in vacuum for the CS2@C50H10 complex predicted that the complex is stable but decomposes at ca. 350 K. The MD simulations in CHCl3 solution showed that the presence of solvent stabilizes the CS2@C50H10 complex in comparison to vacuum. Thus, for the complexes obtained in solution the CO2 gas responsible for the greenhouse effect could be stored in the C50H10 nanotube.