(1R,3S)-Camphoric acid as a building block in supramolecular chemistry: adducts with organic polyamines

(1R,3S)-Camphoric acid [(1R,3S)-1,2,2,-trimethylcyclopentane-1,3-dicarboxylic acid, C10H16O4] forms adducts with a range of amines in which the acid component may be the neutral molecule, the mono-anion (C10H15O4)(-) or the dianion (C10H14O4)(2-). The structures generated by the hard hydrogen bonds take the form of chains in the 1:1 adducts (II) and (III) formed with 4,4'-bipyridyl and 1,2-bis(4-pyridyl)ethane. There are single sheets in the hydrated 1:1 adduct (IV) formed with 1,4-diazabicyclo[2.2.2]octane, and pairwise-interwoven sheets in the 2:1 adduct (V) formed with hexamethylenetetramine. Three-dimensional frameworks are present in the salt-like 1:1 adduct (VI) formed with piperazine and in the hydrated 3:1 adduct (VII) formed with N,N'-dimethylpiperazine. This latter adduct contains both neutral C10H16O4 and anionic (C10H15O4)(-) units. In (II), (III) and (IV), the chain and sheet substructures are linked by C-H...O hydrogen bonds to form three-dimensional frameworks. The monoclinic polymorph of camphoric acid itself (I) has been reinvestigated.