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Zeitschrift für Kristallographie - Crystalline Materials

Ed. by Antipov, Evgeny / Bismayer, Ulrich / Huppertz, Hubert / Petrícek, Václav / Pöttgen, Rainer / Schmahl, Wolfgang / Tiekink, E. R. T. / Zou, Xiaodong

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2,6-Dinitrobenzoic acid and its 2 : 1 salts formed with isomeric n-({[(pyridin-1-ium-n-ylmethyl)carbamoyl]formamido}methyl) pyridin-1-ium, n = 2, 3 and 4

Hadi D. Arman1 / Tyler Miller2 / Pavel Poplaukhin3 / Edward R. T. Tiekink*

1The University of Texas at San Antonio, Department of Chemistry, San Antonio, Texas 78249-0689, U.S.A.

2The University of Texas at San Antonio, Department of Chemistry, San Antonio, TX 78249-0698, U.S.A.

3Chemical Abstracts Service, Columbus, Ohio, U.S.A.

* Correspondence address: The University of Malaya, Department of Chemistry, 50603 Kuala Lumpur, Malaysia,

Citation Information: Zeitschrift für Kristallographie - Crystalline Materials. Volume 228, Issue 6, Pages 295–303, ISSN (Print) 2194-4946, DOI: 10.1524/zkri.2013.1617, May 2013

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This article offers supplementary material which is provided at the end of the article.


The co-crystallisation of two equivalents of 2,6-dinitrobenzoic acid (1) with one equivalent of a member of the isomeric N,N′-bis(pyridin-n-ylmethyl)ethanediamides, n = 2, 3 and 4, resulted in the anticipated 2 : 1 salts, 24. The central core, i.e. CH2N(H)C(=O)C(=O)N(H)CH2, of the isomeric di-cations are superimposable and chemically equivalent pairs of carbonyl, amide and pyridinium groups have an anti conformation. By contrast, the relative orientations of the terminal pyridinium rings from the central core vary significantly across the series as do the relative disposition of the acidic-H atoms. This feature of the structure influences the nature of N—H…O hydrogen bonding and, therefore, the observed supramolecular aggregation patterns. Thus, in 2, the syn-disposition of the nitrogen-bound hydrogen atoms enables the benzoate residue to interact via the two oxygen atoms with both pyridinium- and amine-H atoms to yield a zero-dimensional aggregate. By contrast, in each of 3 and 4, having further distance between the acidic-H atoms, the benzoate residues still interact (either through one both or both oxygen atoms) with pyridinium- and amine-H atoms but those derived from symmetry related molecules to generate one-dimensional aggregates. The three-dimensional architectures of 13 are consolidated, in the main, by C—H…O interactions. The structure of 1 revealed the benzoic acid residue to be perpendicular in contrast to the co-planar conforämations of the nitro groups. In the crystal packing, O–H…O hydrogen bonding lead to a helical supramolecular chain.

Keywords: Salt; Carboxylic acid; Hydrogen bonding; Crystal structure analysis; X-ray diffraction

Supplementary Article Materials

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