Active pharmaceutical ingredients (APIs) with poor physico-chemical properties such as low solubility or inappropriate lipophilicity often present significant challenges in formulation developments and preclinical investigations. For example, APIs with low solubilities often require high dose formulation being administered to obtain the necessary exposure level. So to overcome these problems, it is of particular importance for chemists and pharmaceutical scientists to use chemistry approaches to develop novel molecular API forms with optimum physico-chemical properties at the molecular stage.;This research investigates polymorphism of an antituberculosis drug, 5-chloro-8-hydroxyquinoline, supramolecular conformational isomerism of transition metal-(pyridine-4-acetamide) self-assemblies and structure-activity (specifically solubility and lipophilicity) relationship and stability studies of mixed-ligand metal-drug coordination species.;Some of the known supramolecular chemistry approaches to tune physico-chemical properties of APIs include formation of polymorph, salt, solvate and co-crystal. For all the approaches mentioned above, in the solid material all the ingredients are held together through weak intermolecular forces such as hydrogen bonds, pi-pi interactions and van de Walls forces. Therefore, it is not surprising to explore other types of weak intermolecular forces such as coordination bonds to develop novel molecular API entities. In summary, a few approaches for fine-tuning APIs' physico-chemical properties will be discussed in the thesis using concepts in supramolecular chemistry.
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