title: Salts of maleic and fumaric acids with oxine: the role of isomeric acids in hydrogen-bonding patterns.
abstract: Both maleic and fumaric acid readily form adducts or complexes with other organic molecules. The 1:1 adduct formed by quinolin-8-ol (oxine) with maleic and fumaric acid are salts, namely 8-hydroxyquinolinium hydrogen maleate, C(9)H(8)NO(+).C(4)H(3)O(4)(-), (I), and 8-hydroxyquinolinium hydrogen fumarate, C(9)H(8)NO(+).C(4)H(3)O(4)(-), (II). The cations and anions of both salts are linked by ionic N(+)-H...O(-) hydrogen bonds. The maleate salt crystallizes in the space group P2(1)2(1)2(1), while the fumarate salt crystallizes in P\overline{1}. The maleic and fumaric acids in their complex forms exist as semimaleate and semifumarate ions (mono-ionized state), respectively. Classical N-H...O and O-H...O hydrogen bonds, together with short C-H...O contacts, generate an extensive hydrogen-bonding network. The crystal structures of the maleate and fumarate salts of oxine have been elucidated to study the importance of noncovalent interactions in the aggregation and interaction patterns of biological molecules. The structures of the salts of the Z and E isomers of butenedioic acid (maleic and fumaric acid, respectively) with quinolin-8-ol are compared.
authors.affiliation: Department of Physics, National Institute of Technology, Tiruchirappalli 620 015, Tamilnadu, India.
authors.forename: S
authors.initials: S
authors.lastname: Franklin
authors.forename: T
authors.initials: T
authors.lastname: Balasubramanian
mesh_terms: D018360:Crystallography, X-Ray; D005650:Fumarates / Q000737:chemistry*; D006860:Hydrogen Bonding; D007536:Isomerism; D008298:Maleates / Q000737:chemistry*; D008958:Models, Molecular; D015125:Oxyquinoline / Q000737:chemistry*
chemical_list: D005650:Fumarates; D008298:Maleates; D015125:Oxyquinoline; C032005:fumaric acid; C030272:maleic acid