Supramolecular Behavior of Adenine with Succinic, Fumaric, and Maleic Acids: Tautomerism, Cocrystallization, Salt Formation, and Solvation

The powerful hydrogen bonding capability of adenine makes it a key component of the DNA double helix, while as a crystalline molecular material, these hydrogen bond donors and acceptors make it a good potential cocrystal component possessing distinct physical properties. Here, we report the preparation and structure determination of four adenine-based multicomponent adducts formed with a number of dicarboxylic acids: an anhydrous cocrystal with succinic acid ( 1 ), anhydrous salts with fumaric acid ( 2 ) and maleic acid ( 3 ), and a methanolated salt with maleic acid ( 4 ). The supramolecular behavior of adenine in these materials is discussed in terms of strong hydrogen-bonded bidentate motifs formed between the adenine and acid components and the homomeric adenine synthons retained in these structures. The additional formation of a CH···N interaction on the Watson–Crick site in ( 3 ) enables the stabilization of the unusual 3 H,7 H adeninium tautomer within a purely molecular material.