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
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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+烸H3Cl2O4-, (I), 3-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate, C6H7N2O+烸H3Cl2O4-, (II), and the unusual salt adduct 4-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate-methyl 2-carboxy-4,5-dichlorobenzoate (1/1), C6H7N2O+烸H3Cl2O4-烹H6Cl2O4, (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) ŝ. 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.
Acta Crystallographica. Section C: Crystal Structure Communications
Copyright 2009 International Union of Crystallography. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Published by Blackwell Publishing Ltd. Please refer to the journal's website for access to the definitive, published version.
Physical Chemistry not elsewhere classified