The topology of the charge distribution and the electric-field gradient at the N nucleus in imines and di-imides

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Abstract
A relationship between critical points that define the topology of the Laplacian of a molecular charge distribution ∇2ρ(r), and components of the electric‐field gradient (EFG) tensor at the nucleus of the two‐coordinated N, obtained from an ab initio molecular‐orbital calculation, was found in di‐imides (R–N=N–H with R=H, F, and CN) and imines (RHC=N–H with R=H, F, CN, and CH3). The qzz component of the EFG was found to be determined by the position and magnitude of the nonbonded charge concentration present in the N valence shell, as defined by a maximum in −∇2ρ(r). The orientation of the z axis of the tensor was determined to be associated with three local maxima in −∇2ρ(r) present in the N valence shell while the asymmetry parameter of the tensor was found to be related to saddle points of the N valence shell located above and below the molecular plane.