We present our study on the recognition of hydrogen isotopes by an open-cage fullerene through determination of binding affinity of isotopes H 2/HD/ D2 with the open-cage fullerene and comparison of their relative molecular sizes through kinetic-isotoperelease experiments. We took advantage of isotope H2/D2 exchange that generated an equilibrium mixture of H2/HD/D2 in a stainless steel autoclave to conduct high-pressure hydrogen insertion into an open-cage fullerene. The equilibrium constants of three isotopes with the open-cage fullerene were determined at various pressures and temperatures. Our results show a higher equilibrium constant for HD into open-cage fullerene than the other two isotopomers, which is consistent with its dipolar nature. D 2 molecule generally binds stronger than H2 because of its heavier mass; however, the affinity for H2 becomes larger than D2 at lower temperature, when size effect becomes dominant. We further investigated the kinetics ofH2/HD/D2 release from open-cage fullerene, proving their relative escaping rates. D2 was found to be the smallest and H2 the largest molecule. This notion has not only supported the observed inversion of relative binding affinities between H2 and D2, but also demonstrated that comparison of size difference of single molecules through non-convalent kineticisotope effect was applicable.
|Number of pages||6|
|Journal||Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences|
|State||Published - 13 Sep 2013|
- Open-cage fullerene