An adventure in crystal engineering: Pyridinecarboxamides and their role in supramolecular chemistry

The designed assembly of a 3-D molecular or ionic solid poses the one of the ultimate challenges in the field of crystal engineering. In order to understand the roles that intermolecular forces play, we choose to start with simple building blocks that are designed to create simple architectures. Like synthetic chemists, crystal engineers are concerned with creating a designed product in good yield. Crystal structures that predictably incorporate a designed intermolecular force (i.e. hydrogen bond) contribute to the supramolecular yield.; Herein, we will report the crystal structures of a variety of metal-organic hybrid solids, as well as purely organic solids. Each of these structures will attempt to make use of the carboxamide moiety to link together neighboring complexes or molecules through hydrogen bonds.; Synthesis of eight new substituted phenylpyridines provides one future direction of this research.{09}By making one of the pieces of the puzzle larger, we hope to create larger networks that would have some degree of porosity. Porous metal-organic hybrid materials pose a wealth of potential in crystal engineering, but the charge on the cationic metal ion must somehow be balanced. Many attempts to accomplish this with conventional anions have resulted in the anion taking up space in an otherwise porous architecture. The use of an anionic ligand with hydrogen-bonding functionalities provides a unique approach to this problem.; Multiple hydrogen-bonding moieties in organic architectures are investigated in order to determine the reliability of the acid/pyridine and the amide/amide hydrogen-bonded synthons. In a high-percentage of cases, these two synthons form in a predictable manner, even in the presence of other moieties. They are not as reliable in the presence of some hydroxyl- and amine moieties.; Finally, the design of the first ternary molecule solids is reported. By understanding the competitive nature of hydrogen bonds, according to the Etter Rule, three different compounds associate with one another in a predictable way. By varying one of these compounds we are able to change the color of the crystalline solid. This achieves one of the primary goals of crystal engineering; namely, function through form.