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Issue 7, 2012
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Screening for cocrystals of succinic acid and 4-aminobenzoic acid

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The ability of the pharmaceutically acceptable cocrystallising agents, succinic acid and 4-aminobenzoic acid, to form cocrystals with ten small organic molecules with hydrogen bonding acceptors but no donors, was investigated by grinding, hot-stage microscopy and solution based crystallisation experiments. The reproducible results obtained by different methods showed that only six cocrystals formed. The crystal structures of the four novel cocrystals, succinic acid·2,2′-bipyridine (1 : 1, P21/c, I), succinic acid·diphenylcyclopropenone (1 : 2, P21/c, II), 4-aminobenzoic acid·antipyrine (1 : 1, P21, III) and 4-aminobenzoic acid·phenazine (1 : 2, P[1 with combining macron], IV), are reported. The computed crystal energy landscapes of the cocrystals and their components show why succinic acid·1,4-dicyanobenzene did not form a cocrystal as well as predicting the observed structure of succinic acid·2,2′-bipyridine as the most stable. The most stable hypothetical structures of a 1 : 1 succinic acid·1,4-dicyanobenzene cocrystal are closely related to those of the components. The results demonstrate that cocrystal formation requires both hydrogen bonding and close packing, and so markedly non-planar pharmaceuticals will be quite specific in the steric and hydrogen bonding disposition requirement of coformers.

Graphical abstract: Screening for cocrystals of succinic acid and 4-aminobenzoic acid

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The article was received on 06 Oct 2011, accepted on 05 Jan 2012 and first published on 25 Jan 2012

Article type: Paper
DOI: 10.1039/C2CE06325E
CrystEngComm, 2012,14, 2454-2464

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    Screening for cocrystals of succinic acid and 4-aminobenzoic acid

    N. Issa, S. A. Barnett, S. Mohamed, D. E. Braun, R. C. B. Copley, D. A. Tocher and S. L. Price, CrystEngComm, 2012, 14, 2454
    DOI: 10.1039/C2CE06325E

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