The three-dimensional hydrogen-bonded framework structure in the 1:1 proton-transfer compound of the drug quinacrine with 5-sulfosalicylic acid.

For the hydrated proton-transfer compound 6-chloro-9-[(4-diethylammonio-2-methylbutyl)amino]-2-methoxyacridinium 3-carboxylato-4-hydroxybenzenesulfonate dihydrate, C(23)H(32)ClN(3)O(2+).C(7)H(4)O(6)S(2-).2H(2)O, (I), the conformational features, specifically those of the extended side chain at the 9-position of the acridine parent, have been compared with those of quinacrinium dichloride dihydrate (the drug atabrine or mepacrine). Racemic compound (I) has a three-dimensional hydrogen-bonded framework structure similar to atabrine but also involves the water molecules and both the carboxylate and sulfonate groups of the anion in structure extension. The comparable conformational features found in this uncommon derivative of quinacrine indicate that (I) has potential as a possible pharmaceutical substitute for atabrine.