Acta Crystallographica Section C

Crystal Structure Communications

Volume 65, Part 3 (March 2009)

organic compounds

Acta Cryst. (2009). C65, o103-o107 [ doi:10.1107/S0108270109004405 ]

Zero-, one- and two-dimensional hydrogen-bonded structures in the 1:1 proton-transfer compounds of 4,5-dichlorophthalic acid with the monocyclic heteroaromatic Lewis bases 2-aminopyrimidine, nicotinamide and isonicotinamide

G. Smith, U. D. Wermuth and J. M. White

Abstract: The structures of the anhydrous 1:1 proton-transfer compounds of 4,5-dichlorophthalic acid (DCPA) with the monocyclic heteroaromatic Lewis bases 2-aminopyrimidine, 3-(aminocarbonyl)pyridine (nicotinamide) and 4-(aminocarbonyl)pyridine (isonicotinamide), namely 2-aminopyrimidinium 2-carboxy-4,5-dichlorobenzoate, C₄H₆N₃⁺·C₈H₃Cl₂O₄^-, (I), 3-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate, C₆H₇N₂O⁺·C₈H₃Cl₂O₄^-, (II), and the unusual salt adduct 4-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate-methyl 2-carboxy-4,5-dichlorobenzoate (1/1), C₆H₇N₂O⁺·C₈H₃Cl₂O₄^-·C₉H₆Cl₂O₄, (III), have been determined at 130 K. Compound (I) forms discrete centrosymmetric hydrogen-bonded cyclic bis(cation-anion) units having both R₂²(8) and R₁²(4) N-HO interactions. In (II), the primary N-HO-linked cation-anion units are extended into a two-dimensional sheet structure via amide-carboxyl and amide-carbonyl N-HO interactions. The structure of (III) reveals the presence of an unusual and unexpected self-synthesized methyl monoester of the acid as an adduct molecule, giving one-dimensional hydrogen-bonded chains. In all three structures, the hydrogen phthalate anions are essentially planar with short intramolecular carboxyl-carboxylate O-HO hydrogen bonds [OO = 2.393 (8)-2.410 (2) Å]. This work provides examples of low-dimensional 1:1 hydrogen-bonded DCPA structure types, and includes the first example of a discrete cyclic `heterotetramer.' This low dimensionality in the structures of the 1:1 aromatic Lewis base salts of the parent acid is generally associated with the planar DCPA anion species.

Formula: C₄H₆N₃⁺·C₈H₃Cl₂O₄^-, C₆H₇N₂O⁺·C₈H₃Cl₂O₄^- and C₆H₇N₂O⁺·C₈H₃Cl₂O₄^-·C₉H₆Cl₂O₄


	Structure factor file (CIF format) (122.3 kbytes) [ doi:10.1107/S0108270109004405/gd3270Isup2.hkl ] Contains datablock I

	Structure factor file (CIF format) (137.4 kbytes) [ doi:10.1107/S0108270109004405/gd3270IIsup3.hkl ] Contains datablock II

	Structure factor file (CIF format) (148.9 kbytes) [ doi:10.1107/S0108270109004405/gd3270IIIsup4.hkl ] Contains datablock III

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