Things to do with

11 March 2016 - Nano

Zhang2016.PNGThings to do with a fullerene. Things to do with water and a fullerene. Things to do with water inside a fullerene? Things to do with two water molecules inside a C70 fullerene! This must have been the sort of thinking that went on inside the head of Yasujiro Murata. 15 years ago he brought you endohedral hydrogen fullerene (H2@C60) in a delicate sequence of chemically opening-up a fullerene, stuffing hydrogen inside and closing-up again. In a recent Nature Chemistry article his group repeated this feat but now with water (Rui Zhang et al. DOI). C70 has an inner space of 3.7 by 4.6 Angstrom, large enough to accommodate this cargo. Once the cage was opened, it took 9000 atm of pressure of water in toluene for 40 hours @120°C to get water to enter the cage. After closing-up and work-up H20@C70 was separated from empty C60 by simple HPLC. X-ray diffraction showed that the water molecule was in a disordered state. In the related compound H20@C60 water was very much unmoveable. Could there be room for a double occupancy? Re-examination of the HPLC trace revealed the minor presence of (H2O)2@C70. This compound was not isolated (somewhere there is a rule that "synthesised" means "isolated"?) but is was possible to examine it by spectroscopy (NMR, IR). The dimer was found to rotate quickly at temperatures as low as -80°C. Interestingly even though there is room for 4 hydrogen bonds (in a kind of inverted triangular prism) just one was found to operate.