Salts of maleic and fumaric acids with organic polyamines: comparison of isomeric acids as building blocks in supramolecular chemistry

Abstract

Maleic acid and fumaric acid both readily form adducts with organic diamines: maleic acid usually forms 2:1 adducts with bases, while fumaric acid usually forms 1:1 adducts, and the supramolecular stuctures within the two series are not simply related. The 1:2 adducts formed by 1,2-bis(4-pyridyl)ethane and by 4,4′-bipyridyl, respectively, with maleic acid, compounds (1) and (2), are salts [{(diamine)H2}2+]·[(C4H3O4)−]2 in which the cations lie across a centre of inversion and a twofold rotation axis, respectively. The ions are linked by N—H...O hydrogen bonds into three-ion aggregates, which are further linked by C—H...O hydrogen bonds into two- and three-dimensional arrays, respectively. In the fumarate salts formed by 2,2′-dipyridylamine (1:1) and 1,4-diazabicyclo[2.2.2]octane (1:2), compounds (3) and (4), the ionic components are linked into molecular ladders. The 1:1 adduct of 4,4′-bipyridyl and fumaric acid, compound (5), contains two neutral components, both of which lie across centres of inversion; these components are linked into chains by a single O—H...N hydrogen bond and thence into sheets by C—H...O hydrogen bonds. The corresponding adduct formed by 1,4-diazabicyclo[2.2.2]octane, compound (6), is a salt that again contains chains linked into sheets by C—H...O hydrogen bonds. In the 1:1 adducts, compounds (7), (8) and (10), that are formed between 1,2-bis(4-pyridyl)ethane, 4,4′-trimethylenedipyridine and hexamethylenetetramine, respectively, with fumaric acid, and in the 1:2 adduct, compound (9), of 2,2′-dipyridylamine and maleic acid, the chains that are generated by the hard hydrogen bonds are linked by C—H...O hydrogen bonds to form, in each case, a single three-dimensional framework. In the 1:1 adduct, compound (11), of 2,2′-bipyridyl and fumaric acid the hydrogen bonds generate two interwoven three-dimensional frameworks.