Formation of quinol co-crystals with hydrogen-bond acceptors

Oswald, I D H and Motherwell, W D S and Parsons, S (2005) Formation of quinol co-crystals with hydrogen-bond acceptors. Acta Crystallographica Section B: Structural Science, 61 (Part 1). pp. 46-57. ISSN 0108-7681

Abstract

The crystal structures of eight new co-crystals of quinol with pyrazine, piperazine, morpholine, pyridine, piperidine, 4,4'-bipyridine, N-methylmorpholine and N,N'-dimethylpiperazine are reported. Quinol forms 1: 1 co-crystals with pyrazine, piperazine and N, N'-dimethylpiperazine, but 1: 2 co-crystals with morpholine, 4,4'-bipyridine, N-methylmorpholine, pyridine and piperidine. This difference can be rationalized in most cases by the presence of, respectively, two or one strong hydrogen-bond acceptor(s) in the guest molecule. The exception to this generalization is 4,4'-bipyridine, which forms a 1: 2 co-crystal, possibly to optimize crystal packing. All structures are dominated by hydrogen bonding between quinol and the guest molecules. A doubly bridging motif, which connects pairs of quinol and guest molecules via NH...O or CH...O interactions, is present in all but the sterically hindered N, N'-dimethylpiperazine and N-methylmorpholine co-crystals.

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