Investigation of solid materials and their transformation processes by X-ray and complementary analytical techniques

The work presented in this thesis concerns the investigation of a family of cinnamic acid derivatives. A combination of complementary analytical techniques is used to explore detailed structural aspects, and subsequently, chemical and physical properties of some of the materials. The crystal structures of the materials have been determined by single crystal X-ray diffraction techniques. Chapter 1 reviews the relevant background knowledge including crystal engineering aspects and supramolecular chemistry, intermolecular interaction, polymorphism in crystalline materials, solid state processes such as phase transformation and solid state photoreaction, cocrystallization, and the mechanogrinding approach. Chapter 2 provides background information relating to the main experimental techniques employed in this work. These include single crystal X-ray diffraction, powder X-ray diffraction, thermal analysis (deferential scanning calorimetry) and high performance liquid chromatography. Chapter 3 explores the polymorphism of meta-substituted-cinnamic acids and phase transformation between related polymorphs, resulting in the discovery of two rare cases of transformation of cinnamic acids, in which the two forms of the same polymorphic classification. Chapter 4 investigates the feasibility of the cocrystallization of binary systems that contain the different cinnamic acids studied in Chapter 3, resulting in the discovery and characterization of several crystal structures of different binary systems. The binary systems investigated by a combination of thermal analysis and PXRD, revealing information on the effect of the components on the obtained structure. Chapter 5 investigates the structural aspects of K+ and NH+ salts of the different cinnamic acids investigated in Chapter 3. The study extended to explore the feasibility of cocrystallization of different binary salts systems (bi-anion or bi-cation salts), resulting in the design of materials that undergo photodimerization reaction. The study also provides considerable information on the effect of the substituents and the cations on the structure obtained. Chapter 6 gives evidence of the occurrence of the photodimerization process in several solid systems (investigated in previous chapters) in which the structures showed optimal arrangement of the double bond. The work also includes the reaction occurring in some binary solid solution systems, revealing a random molecular distribution of molecules throughout the reactant crystalline materials. The study also investigates the photoreaction in systems exhibiting a criss-cross arrangement of the double bonds, providing information on the dimerization and oligomerization of the materials. Chapter 7 reports interesting insights into the green chemistry approach of mechanogrinding and solvent drop grinding of a system contains 3-BrCA and 3-ClCA. Cocrystallization and the phase control is achieved via the process. Chapter 8 gives an overview on the future work