A metal-organic nanotube (MON) has been synthesized with the uranyl unit (UO22+) and iminodiacetic acid via solvent diffusion. The MON contains channels of diameter 1.2 nm that are occupied by hexameric water molecules that arrange themselves into a chair fashion. Initially it was thought that this arrangement of water molecules mimicked that of hexameric ice (Ih). However, under further scrutiny it appears these solvent molecules take a shape similar to high pressure phases, such as ice (II). This rare high pressure polymorph of ice is thought to only exist extra terrestrially, as in the cores of the moons of Jupiter. Furthermore, upon variable temperature crystallographic interrogation we observe subtle changes in the unit cell dimensions of the MON that suggest possible phase changes of the confined water around 250 K. These subtle, yet significant perturbations suggest the expansion and contraction of the confined water is having a structural impact on the MON even though there lacks explicit interaction between this solvent and the tube interior.

Water confinement properties of a metal-organic nanotube

253rd National Meeting (2017)

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