Influence of cooperativity on hydrogen bond networks

Cooperative effects are known to strongly affect the geometrical, energetic and vibrational properties of hydrogen bonded systems. In particular, such effects strongly favor molecular arrangements where each molecule is simul taneously a donor and an acceptor of hydrogen bonds (HBs), regardless of th e chemical nature of the monomer subunits. In the particular case of water systems, it has been shown that the more a molecule is a proton donor in HB s, the more the HBs where it is a proton acceptor are reinforced. Such a pr operty could be at the origin of the equilibrium between the two species of hydrogen bonded water molecules in liquid water (one with a strong hydroge n bonding character, and one with a weaker one), as experimentally evidence d and as a molecular dynamic study of the small (H2O)(24) cluster clearly s uggests.