Host-guest hydrogen bonding in high-pressure clathrates

Clathrate hydrates are crystalline compounds consisting of hydrogen-bonded water molecules configured into cages enclosing guest molecules that are typically non-polar. Studies of the last decades evidence that polar molecules may nonetheless be enclathrated, producing stable solid phases in the presence of clathrate promoters, with the formation of guest-host hydrogen bonds. So far, this phenomenon has been studied only for the common sI, sII, and sH binary clathrates while host-guest hydrogen bonding in HP dense clathrates have not been addressed. Recently, we have synthesised at HP-LT conditions several dense acetone clathrates featuring hydrogen bonging between oxygen of the acetone molecule and a framework oxygen. Here we propose to further investigate high-pressure clathrates with different polar guest molecules by means of in situ SCXRD in order to address the effect of host-guest hydrogen bonding on clathrates thermodynamic stability, compressibility, and thermal expansion.