The Hydrogen Bond: A Hundred Years and Counting

Abstract

Since its original inception, a great deal has been learned
about the nature, properties, and applications of the H-bond. This review
summarizes some of the unexpected paths that inquiry into this phenomenon
has taken researchers. The transfer of the bridging proton from one
molecule to another can occur not only in the ground electronic state,
but also in various excited states. Study of the latter process has developed
insights into the relationships between the nature of the state,
the strength of the H-bond, and the height of the transfer barrier. The
enormous broadening of the range of atoms that can act as both proton
donor and acceptor has led to the concept of the CH···O HB, whose
properties are of immense importance in biomolecular structure and
function. The idea that the central bridging proton can be replaced by
any of various electronegative atoms has fostered the rapidly growing
exploration of related noncovalent bonds that include halogen, chalcogen,
pnicogen, and tetrel bonds.