Structural systematics and conformational analyses of a 3 × 3 isomer grid of nine N-(tolyl)pyridinecarboxamides and three chlorinated relatives?

CrystEngComm Pub Date: 2011-04-28 DOI: 10.1039/C1CE05169E

Abstract

A 3 × 3 isomer grid of nine N-(tolyl)pyridinecarboxamides (NxxM, x = para-/meta-/ortho-) integrating crystal structure analyses, ab initio calculations (gas phase and PCM-SMD solvated in CH2Cl2, H2O) and conformational studies is described. Three 5-Cl-NoxM derivatives (side-products from the NoxM syntheses) and NmpFM (a 50?:?50 mixture of NmpF and NmpM) are reported. The six NpxM/NmxM isomers aggregate via N–H?N or N–H?O[double bond, length as m-dash]C hydrogen bonds, whereas the six NoxM/5-Cl-NoxM structures exhibit intramolecular N–H?N interactions influencing co-planarity. The NmmM isomer is isomorphous and isostructural with its bridge-flippedMmm isomer providing a rare case of isostructuralism between such isomers. Our objectives are to (a) understand correlations between the p-/m-/o-N/CH3 substituent permutations with solid state molecular conformations and supramolecular aggregation, (b) explain the influence of molecular conformation on inter/intramolecular interactions, (c) correlate physico-chemical properties and (d) compare and rationalise differences between crystal and calculated structures.

Graphical abstract: Structural systematics and conformational analyses of a 3 × 3 isomer grid of nine N-(tolyl)pyridinecarboxamides and three chlorinated relatives
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