Ice-Like Dynamics of Water Clusters

Abstract

Understanding certain behaviors of water, e.g., its dynamics, is extremely important in various fields. Recently, using 1 H nuclear magnetic resonance spectroscopy, we have identified a metastable state of water molecules, i.e., water clusters, in hydrophobic solvents in addition to dissolved water molecules and a small bulk water domain. However, the low abundance of water clusters made observing their dynamics challenging. In this study, the dynamics of water clusters in benzene-d 6 were investigated by quasi-elastic neutron scattering measurements using the AGNES time-of-flight spectrometer of the Japan Research Reactor JRR-3. The diffusion dynamics of the hydrogen atoms were much slower than those of bulk water (with a self-diffusion coefficient of 1.15 × 10 −9 m 2 /s at 273 K) and even slower than the upper-limit dynamics at the observable scale (10 −10 m 2 /s). The dynamics of water clusters are slow, "like ice", even at 283−303 K, which is above the freezing point of water (273 K).

Supramolecular polynuclear clusters sustained cubic hydrogen bonded frameworks with octahedral cages for reversible photochromism

“…However, this concept has been rarely discussed in the design of HOFs with regular porosity, as HOFs are assembled by rigid building molecules through intermolecular hydrogen bonding 19 – 24 . Pristine hydrogen bonding interactions are too weak to stabilize rigid and directional polynuclear clusters 25 – 28 . The rational synthesis of porous HOFs with preorganized and highly symmetrical networks has been a long-term challenge 29 .…”