A new supramolecular heterosynthon [C-I•••O=C(carboxylate)] at work: engineering copper acetate cocrystals

A carboxylate center dot center dot center dot iodine supramolecular heterosynthon can be reliably applied in cocrystal engineering, using metal carboxylates as building blocks. Analysis of the energy framework of the exemplary paddlewheel crystal [Cu(OAc)(2)MeOH](2) indicates a robust 1D chain and even 2D layer long-range synthon modules, which can be intactly transferred into cocrystals. However, this approach allows the identification of a weak link - i.e. layers where the C-H center dot center dot center dot O=C hydrogen bonds between ([Cu(OAc)(2)(MeOH)](2))(n) polymeric chains will be subject to substitution by I center dot center dot center dot O=C halogen bonds during interaction with halogen bond donor co-formers. In contrast to the O-H center dot center dot center dot O=C/C-H center dot center dot center dot O=C catemeric crystals of pure acetic acid, the crystal design exercise based on the I center dot center dot center dot O=C(carboxyl) supramolecular synthon afforded a 1 : 1 cocrystal of 1,4-C6F4I2 and CH3COOH, where the discrete centrosymmetric dimers of acetic acid are stabilized by I center dot center dot center dot O=C(carboxyl) halogen bonds.