- Mechanochemical reaction kinetics and mechanisms
This project will study the chemical kinetics of mechanochemical reactions in a ball mill toward the determination of their activation energies, and toward testing the validity of a stress-enhanced thermal activation model. In situ studies will be done without interrupting the reactions by using Raman spectroscopy, while ex situ measurements will be done (for some reactions) by stopping them and analyzing the products by laboratory X-ray powder diffraction (quantitative phase analysis), sometimes combined with Raman spectroscopy. Several reaction types will be studied, such as Diels Alder cycloadditions, MOF syntheses, and organic cocrystallization reactions.
- Mechanochemical synthesis of binary and ternary organic cocrystals with potential ferroelectric properties, crystal growth, and solid-state properties characterization
Students will synthesize by mechanochemistry binary and ternary hydrogen-bonded organic cocrystals. X-ray powder diffraction will be used for the identification of products and leftover reactants. Once new materials are identified, single crystals (for crystal structure determination) will be grown. The solid-state properties of the new materials prepared will be characterized by various techniques, such as FT-IR and Raman spectroscopies, thermogravimetry, differential scanning calorimetry, optical microscopy, SEM, and solid-state NMR. Thin films will be prepared for the study of the ferroelectric properties. Crystallographic phase transitions at low temperatures will be investigated by single crystal X-ray diffraction and FT-IR spectroscopy as a function of the temperature. A Bruker D8 QUEST ECO X-ray single crystal diffractometer including cryogenic attachments (80 – 400 K) will be used for crystal structure analysis.
- Synthesis and study of relevant solid-state properties of pharmaceutical co-crystals, drug-drug co-crystals and salts
Pharmaceutical co-crystals are new drug delivery forms with improved properties (e.g., increased solubility, chemical stability, etc), composed of a pharmaceutically active ingredient and another molecule (a co-crystal former). Drug-drug co-crystals are made of two pharmaceutically active compounds. These materials can be synthesized by mechanochemistry and solution chemistry and their crystal structures obtained from X-ray laboratory or synchrotron powder diffraction or single crystal diffraction data. We will use additional solid-state techniques to study relevant properties (e.g., thermogravimetry, differential scanning calorimetry, FT-IR spectroscopy, melting point, optical microscopy, NMR, etc.). The Cambridge Structural Database and software can be used to design suitable co-crystallizing pairs.
Different polymorphs (crystal structures) can be synthesized by milling the reactants with small volumes of different organic solvents. Synthetic/preparative methods for students to practice are liquid-assisted grinding (in a ball mill) and single crystal growth. Solid-state characterization techniques are X-ray and neutron powder diffraction, single-crystal X-ray diffraction, Raman spectroscopy, FT-IR spectroscopy (it can be as a function of the temperature, in collaboration), magnetic susceptibility, and others such as thermogravimetry, differential scanning calorimetry, solid-state NMR, optical microscopy, SEM, melting point determination, etc.)
- Development of the software WinPSSP
PSSP and WinPSSP are computer programs applying direct-space methods for the crystal structure determination of organic materials from X-ray powder diffraction. We will elaborate and test modifications in the search algorithm of PSSP (in C/C++ programming language), to improve its structure solution search performance. We will also elaborate instructional materials for undergraduates.