The crucial role of water in shaping low-barrier hydrogen bonds

Low-barrier hydrogen bonds (LBHBs) are key components in a range of chemical processes, often appearing in metal-mediated catalytic applications. The formation of LBHBs has generally been attributed to the particular geometric arrangement of the surrounding atoms and molecules, yet few specific atomic-level details have emerged. In this study, several metal maleate tetrahydrates have been studied using a combination of solid-state density functional theory, terahertz spectroscopy, and X-ray diffraction to evaluate the significance of both water molecules and metal cations in guiding LBHB formation and function. The findings reveal the assumption that metal identity is of paramount importance to be incomplete, and that the metal cation does not directly influence the LBHB in the maleate ligand. Rather, the characteristics are regulated by water molecule positioning, asserting the critical role of water in governing LBHBs and providing new insight into their formation mechanisms.