Probing the Electronic Properties and Interaction Landscapes in a Series of N -(Chlorophenyl)pyridinecarboxamides.

A 3 × 3 isomer grid of nine N -(chlorophenyl)pyridinecarboxamides ( NxxCl ) is reported with physicochemical studies and single crystal structures ( Nx = pyridinoyl moiety; xCl = aminochlorobenzene ring; x = para -/ meta -/ ortho -), as synthesized by the reaction of the substituted p -/ m -/ o -pyridinecarbonyl chlorides ( Nx ) with p -/ m -/ o -aminochlorobenzenes ( xCl ). Several of the nine NxxCl crystal structures display structural similarities with their halogenated NxxX and methylated NxxM relatives ( x = p -/ m- / o -substitutions; X = F, Br; M = methyl). Indeed, five of the nine NxxCl crystal structures are isomorphous with their NxxBr analogues as the NpmCl / Br , NpoCl / Br , NmoCl / NmoBr , NopCl / Br , and NooCl / Br pairs. In the NxxCl series, the favored hydrogen bonding mode is aggregation by N-H···N pyridine interactions, though amide···amide intermolecular interactions are noted in NpoCl and NmoCl . For the NoxCl triad, intramolecular N-H···N pyridine interactions influence molecular planarity, whereas NppCl·H 2 O (as a monohydrate) exhibits O-H···O, N-H···O1W, and O1W-H···N interactions as the primary hydrogen bonding. Analysis of chlorine-containing compounds on the CSD is noted for comparisons. The interaction environments are probed using Hirshfeld surface analysis and contact enrichment studies. The melting temperatures ( T m ) depend on both the lattice energy and molecular symmetry (Carnelley's rule), and the melting points can be well predicted from a linear regression of the two variables. The relationships of the T m values with the total energy, the electrostatic component, and the strongest hydrogen bond components have been analyzed.