Mapping of N−C Bond Formation from a Series of Crystalline Peri‐Substituted Naphthalenes by Charge Density and Solid‐State NMR Methodologies

A combination of charge density studies and solid state nuclear magnetic resonance (NMR) (1) J (NC) coupling measurements supported by periodic density functional theory (DFT) calculations is used to characterise the transition from an n–π* interaction to bond formation between a nucleophilic nitrogen atom and an electrophilic sp (2) carbon atom in a series of crystalline peri‐substituted naphthalenes. As the N⋅⋅⋅C distance reduces there is a sharp decrease in the Laplacian derived from increasing charge density between the two groups at ca. N⋅⋅⋅C = 1.8 Å, with the periodic DFT calculations predicting, and heteronuclear spin‐echo NMR measurements confirming, the (1) J (NC) couplings of ≈3–6 Hz for long C−N bonds (1.60–1.65 Å), and (1) J (NC) couplings of <1 Hz for N⋅⋅⋅C >2.1 Å.