title: 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.
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, C(4)H(6)N(3)(+).C(8)H(3)Cl(2)O(4)(-), (I), 3-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate, C(6)H(7)N(2)O(+).C(8)H(3)Cl(2)O(4)(-), (II), and the unusual salt adduct 4-(aminocarbonyl)pyridinium 2-carboxy-4,5-dichlorobenzoate-methyl 2-carboxy-4,5-dichlorobenzoate (1/1), C(6)H(7)N(2)O(+).C(8)H(3)Cl(2)O(4)(-).C(9)H(6)Cl(2)O(4), (III), have been determined at 130 K. Compound (I) forms discrete centrosymmetric hydrogen-bonded cyclic bis(cation-anion) units having both R(2)(2)(8) and R(1)(2)(4) N-H...O interactions. In (II), the primary N-H...O-linked cation-anion units are extended into a two-dimensional sheet structure via amide-carboxyl and amide-carbonyl N-H...O 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-H...O hydrogen bonds [O...O = 2.393 (8)-2.410 (2) A]. 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.
authors.affiliation: School of Physical and Chemical Sciences, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. g.smith@qut.edu.au
authors.forename: Graham
authors.initials: G
authors.lastname: Smith
authors.forename: Urs D
authors.initials: UD
authors.lastname: Wermuth
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: White
mesh_terms: D006860:Hydrogen Bonding; D015394:Molecular Structure; D009536:Niacinamide / Q000737:chemistry*; D010795:Phthalic Acids / Q000737:chemistry*; D011522:Protons; D011743:Pyrimidines / Q000737:chemistry*
chemical_list: C527950:4,5-dichlorophthalic acid; D010795:Phthalic Acids; D011522:Protons; D011743:Pyrimidines; C012180:2-aminopyrimidine; D009536:Niacinamide; C027681:isonicotinamide