Thermal expansion along one-dimensional chains and two-dimensional sheets within co-crystals based on halogen or hydrogen bonds

The ability to vary the thermal expansion parameters within halogen- or hydrogen-bonded co-crystals is reported. An acceptor molecule, 1,2-bis(4-pyridyl)acetylene, was selected due to its ability to form supramolecular one-dimensional chains, regardless of the ditopic donor type. We demonstrate that the smallest expansion occurs along the chain, and greater expansion occurs within the two-dimensional sheet, which is based on weaker halogen interactions.