An Investigation of the Hydrogen-Bond Preferences and Co-crystallization Behavior of Three Didonor Compounds.

We assess the suitability of the three didonor compounds as building blocks for ternary co-crystals of the type (didonor)(monoacceptor)<sub>2</sub>. A Cambridge Structural Database (CSD) survey was carried out to analyze the hydrogen-bond connectivity and develop a strategy for the preparation of the desired co-crystal. Six specific compounds were selected and crystals were grown from 1:1 and 1:2 solutions of didonor compounds (<i>m</i>-hydroxybenzoic acid, <i>p</i>-hydroxybenzoic acid, and racemic mandelic acid) and acceptor compounds (acridine, triphenylphosphine oxide, and nicotinamide) leading to three co-crystals (<i>m</i>-hydroxybenzoic acid)·(triphenylphosphine oxide)<sub>2</sub> (<b>1</b>), ((<i>RS</i>)-mandelic acid)·(acridine) (<b>2</b>) and (<i>p</i>-hydroxybenzoic acid)·(nicotinamide) (<b>3</b>). Characterization by single-crystal structure determination confirms the success of this design strategy.