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 3H,7H adeninium tautomer within a purely molecular material.