Benzidine: A co-crystallization agent for proton acceptors

The search for co-crystals of amines as bifunctional hydrogen-bond donors with bidentate oxygens as bifunctional hydrogen-bond acceptors, as part of a program to investigate the utility of using the R-4(2) (8) hydrogen-bonding motif, has yielded three co-crystals of benzidine with p-benzoquinone, diphenyl sulfoxide, and triphenylphosphine oxide. The crystal structures for all three materials are reported. Only the co-crystal structure of benzidine/diphenyl sulfoxide/water reveals the desired motif.