Hydrogen-bond geometry and its isotope effect in crystals with OHO bonds—revisited

Abstract

The O–H vs O⋯O correlation in OHO hydrogen bonds is briefly reviewed based on the development during these twenty years and the geometric isotope effect ΔR is revised including the new data. It is pointed out that the following still remains to be settled: (1) whether or not the O–H distances in asymmetric bonds for the same O⋯O distance scatter in short hydrogen bonds at low temperature; (2) whether there exists or not the exceptional compounds that exhibit the extraordinarily large geometric isotope effect (∼0.1Å); (3) where the critical hydrogen-bond distance is located; and (4) the peculiar hydrogen-bond geometry and its origin in high-pressure ice.