A cooperation molecular recognition study: syntheses and analysis of supramolecular assemblies of tetrafluoroterephthalic acid with some aza compounds

Abstract

A series of new molecular complexes, both co-crystals and salts, constructed by tetrafluoroterephthalic acid with various aza compound moieties, 3-hydroxypyridine, 2-aminopyrimidine, 4-dimethylaminopyridine, 4,4′-bipyridine, 2,5-bis(4-pyridyl)-1,3,4-oxadiazole, o-phenanthroline, and imidazole have been analyzed with respect to synthons presented in the crystal structures. These new forms are characterized by single crystal X-ray diffraction, infrared spectroscopy, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). A family of supramolecular reagents containing different binding sites were allowed to react with tetrafluoroterephthalic acid in order to assemble individual molecules into larger architectures with precise intermolecular interactions, using a combination of hydrogen- and halogen-bonds. Single crystal X-ray diffraction studies show that, the –COOH/–COO⁻ group acceptor consistently seeks out the basic co-former donor generating the most important intermolecular interaction in all organic complexes. The hydrogen bond patterns exhibited with the aza compounds were found to depend on the nature and position of the substituents. The results can be rationalized through a hierarchical view of intermolecular interactions based upon observed structural pattern preferences, and they also show the reliability of tetrafluoroterephthalic acid as an effective supramolecular tool, even in the presence of other potential disruptive hydrogen-bonding donor–acceptor moieties. These results also illustrate how two different noncovalent interactions can be employed side-by-side in the reliable construction of extended molecular networks with predictable connectivity and dimensionality. With o-phenanthroline forming hydrates, the water molecule plays a central role in synthon formation and crystal packing. After the formation of 1–8, the melting points are dramatically different, and thermal stabilities of these compounds have been investigated.