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Figure 4
(a) The homodimeric and (b) the heterodimeric primary recognition units of cyclic imide–hydroxybenzoic acid combinations. (c) A tetrameric unit comprising a hydroxyl-supported imide homodimer (Thomo-II) can propagate through carboxylic acid homodimers to form co-crystals. (d) and (e) Similarly, the progression of tetrameric units can result in co-crystals. (f) Propagation of the Thetero unit can take place through OH substitution at meta-positions (indicated by red circles), which confers stronger O—Hhydroxyl⋯O=Cimide auxiliary interactions (compared with C—H⋯O=C) and therefore gives rise to co-crystals. Dashed lines indicate hydrogen bonds. Eutectics, which are hallmarked by finite and discrete units, can be formed for combinations where tetrameric units are not stabilized and/or propagated.

Volume 2| Part 3| April 2015| Pages 341-351
ISSN: 2052-2525