RUI: Theoretical Studies of Non-Covalent Interactions and Chemical Bonding Transitions Across Phases in Inorganic Systems, and Investigations of Other Modes of Weak Bonding

In this project funded by the Chemical Structure Dynamics and Mechanisms-A (CSDM-A) program of the Chemistry Division, Professor Kelling Donald of the University of Richmond is using theoretical methods to understand the interactions between molecules in chemical systems where particularly weak interactions are important. It is well-known in modern chemistry that atoms and molecules can interact with each other in very strong ways to form new compounds and in weak ways that can be more readily reversed or disrupted.

For the latter case, however, even though the interactions are relatively weak, they can be very important. Weak interactions allow geckos to climb walls, for instance, and have other demonstrable effects in nature, and in research laboratories. This project investigates classes of chemical systems where weak interactions are crucial.

Such systems include compounds of the metal halide class that form solids stabilized by weak interactions, in some cases, but not in other cases. The project is dedicated in part to elucidating why the solids of some metal halides are held together only by weak interactions in certain cases, but those weak interactions are overtaken by much more powerful forces in other metal halides.

The focus is on using mathematical and computational tools to further our understanding of how weak interactions transition to strong chemical bonding and, in turn, to better predict new and interesting materials properties. This project will engage undergraduates and post-baccalaureate students in faculty-guided research and provide high school students from diverse backgrounds with mentored research experiences, and help them to acquire academic skills that are crucial for success in college.

This project under the guidance of Professor Kelling Donald at the University of Richmond (UR) aims to rationalize the bonding transition phenomenon in which chemical systems such as the binary dihalide mercury difluoride, move during the oligomerization process from weak van der Waals-type bonding in clusters to polar covalent inter-monomer bonding, eventually converging upon an ionic solid structure. These studies are aimed at elucidating the fundamental basis and the evolution of this phenomenon where it exists among the halides, hydrides, and oxides of other heavy main group and d-block metals.

The Donald group will also examine the role of relativistic effects in these phenomena. Another class of weak interactions under examination here is halogen bonding and other so-called sigma hole interactions, which continue to be implicated in biology and in the crystal engineering of organohalides. A goal in this work is to advance understanding of that phenomenon for organic and inorganic halides, and other unusual bonding modes in systems such as fluxional organometallic and potential ouroboric ring compounds.

Professor Donald’s undergraduate students will perform the majority of the proposed work, and high school students from diverse backgrounds will participate in a research/mentoring program devised by Professor Donald, which will focus on attracting high school juniors from underrepresented groups and potential first-generation college students for (i) hands-on activities in research labs at UR, (ii) direct discussions with UR professionals on study skills, stress management, and other key competencies, and (iii) summer research fellowships.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.