N-H…O intramolecular hydrogen bonds - The influence of external agents on π-electron delocalization

N-H…O and O-H…N intramolecular hydrogen bonds are analyzed theoretically at MP2/6-311++G(d,p) level of approximation. The influence of the external agents: Li+, Na+, HF and HCl Lewis acids, on the pseudo ring of conjugated single and double bonds closed by hydrogen bond is investigated. These external agents are responsible for the enhancement of π-electron delocalization and the equalization of conjugated bonds but it does not correspond to the strengthening of hydrogen bonding. The Bader theory is also applied to indicate and to analyze critical points. The characteristics of bond and ring critical points are determined to deepen the nature of π-electron delocalization and of hydrogen bond interaction.