Aryl-substituents moderate the nature of hydrogen bonds, N-H⋯N versus N-H⋯O, leading to supramolecular chains in the crystal structures of N-arylamino 1,2,3-triazole esters

Abstract

Structural analysis reveals the presence of supramolecular chains in a series of eight N-arylamino 1,2,3-triazole esters, which differ only in the nature of the substituent (Y) of the terminal aryl ring. In each of 1 (Y = 4-H), 3 (4-Cl), 4 (4-Br), 5 (4-I) and 6 (4-OMe), the chains are sustained by N-H⋯N hydrogen bonding. In 2 (Y = 4-F) and 8 (Y = 2,5-Cl2), the chains are mediated by alternating N-H⋯N and N-H⋯O hydrogen bonding, whereas in 7 (Y = 4-NO2) the chain is sustained by N-H⋯O hydrogen bonding only. While the differences in the adopted supramolecular motifs are qualitatively correlated with the electronegativity of the Y substituents, no quantitative correlations could be made with the electronic structures of the theoretical gas-phase molecules. Two distinct patterns of crystal packing are observed, with the first of these being based on the inter-digitation of layers, comprised of supramolecular chains and connections of the type C-X⋯π(aryl) between them for 3-5 and 8; only weak off-set edge-to-edge π⋯π interactions were noted in the case of 1. A common feature of the zigzag chains in these crystal structures was a syn-disposition of successive aryl rings along the axis of propagation. The remaining structures adopted three-dimensional architectures where the Y substituents of the anti-disposed aryl rings participated in F⋯H (2) or C-H⋯O (6 and 7) interactions. A detailed analysis of the Hirshfeld surfaces and fingerprint plots for 1-8 enabled a comparison of the intermolecular interactions involved in constructing the disparate supramolecular architectures. In the structures featuring N-H⋯N hydrogen bonding leading to the supramolecular chain, the maximum contribution to the overall crystal packing was less than 20%. This increased to over 25% in the case where there was exclusive N-H⋯O hydrogen bonding in the chain. © 2013 The Royal Society of Chemistry.