Intramolecular hydrogen bonding (IHB) of 1-amino-3-imino-prop-1-ene (AIP), as the simplest resonance-assisted hydrogen bond system in symmetric N–H· · ·N class, and its halo derivatives (F, Cl, and Br) have been studied at the DFT-B3LYP/6-311++G∗∗ level of theory. For better understanding of the nature of substituent effects, nitro and methoxy derivatives of AIP were also added to our consideration. Good linear correlations between IHB energies based on Espinosa’s equation and −G(r)/V(r ) values, total electronic density, Laplacian of total electronic density in critical points, π-electron delocalization parameter (Q), hyper conjugative interaction energy of lp(N)→ σ∗(N–H), (Fi, j /Si, j )2 parameter, natural charges of bridged hydrogen, frequency shift of the N–H stretching vibration, and chemical shift of bridged hydrogen were obtained.

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