Unconventional interaction in N(P)-related systems

Non-conventional intramolecular and intermolecular interactions have been investigated employing glycine (VIIp), NH3⋯HCl, NH3⋯H2O and PH3⋯H2O as model systems. Geometries and harmonic frequencies were determined at a correlated ab initio level, which shows a elongating of the Cl–H or O–H bond of the proton donor and a red-shifting of the corresponding Cl–H or O–H bond stretching frequency. NBO analysis indicates there is a significant charge transfer from the proton acceptor to the proton donor. However, this type of interaction cannot be called hydrogen bond according to a comparative analysis of electron density topology in the four systems.