Investigation of relationship between Spinosa and Shuster methods and describing parameters of bond in gas phase

Investigation of O-H…O intramolecular hydrogen bond (IMHB) in N-formal formamidicacid(NFF) and its derivatives were performed and their IMHB energies were obtained usingthe shuster and Spinosa methods.[1,2] Also the topological properties of electron densitydistribution and charge transfer energy associated with IMHB were gained by quantumtheory of atoms in molecules and natural bond orbital theory, respectively.