Cubanecarboxylic acids. Crystal engineering considerations and the role of C-H...O hydrogen bonds in determining O-H...O networks

The synthesis and structural characterization of a family of 4-substituted-1-cubanecarboxylic acids are described. The results showed that four of the seven crystal structures contain the unusual syn-anti O-H...catemer. These compounds were 4-chloro-1-cubanecarboxylic acid, 4-bromo-1-cubanecarboxylic acid, 4-iodo-1-cubanecarboxylic acid and 4-(methoxycarbonyl)-1-cubanecarboxyillic acid. This is attributed to the stabilization from C-H...O bonds formed by the acidic cubyl C-H donors and the carboxyl O-acceptor atoms.