Binary and ternary co-crystals and molecular salts of 3,5-dinitrobenzoic acid: A many-faceted supramolecular reagent

The co-crystallization of 3,5-dinitrobenzoic acid (DNBA) to form binary and ternary complexes is reported. Binary complexes (DNBA) (flouranthene) (1), (DNBA) (9-bromoanthracene) (2), (DNBA) (9-methylanthracene) (3) and (DNBA) (9-anthroic acid) (4) are all sustained by charge-transfer interactions. By introducing three different pyridine complexes, the ternary complexes (DNBA) (flouranthene) (5-nitro-2-aminopyridine) (5), (DNBA) (9-anthracenecarboxylic acid)∙(3-bromo-2-aminopyridinium) (6) and (DNBA) (9-anthroic acid) (3-nitro-2-aminopyridine) (7) were synthesized utilizing an additional classical hydrogen bond from the DNBA to the pyridine. Compound 6 formed a molecular salt via proton exchange between the DNBA and 3-bromo-2-aminopyridine, whereas all other complexes are neutral (co-crystals).