Tailoring the Properties of Molecular Assemblies via Noncovalent Interactions

Molecular scale noncovalent interactions pervade biological, materials, and chemical systems. Although relatively weak on an individual level, they can have a strong impact on molecular structuring and dynamics when acting in concert. The effects of hydrogen bonding are well-known, while the analogous interaction in some halogen-containing molecules, termed halogen bonding, is far less studied.

The extent that halogen bonding can direct the assembly of supramolecular structures with specific material characteristics is undetermined. Through the proposed studies, a new modeling paradigm will be developed that aims to provide unique chemical insight regarding the connectivity between the molecular-level and larger-scale material properties. This work is significant because it will identify molecular signatures in halogen bond donors and acceptors that control the assembly of these building blocks into supramolecular structures, thereby advancing our understanding of what dictates the material properties and providing a chemical route to modulate the observed behavior.

The predictive approach represents an entirely new way to think about designing suprastructures with desired properties from the bottom up using noncovalent interactions as the assembly mechanism. The tunability of halogen bonds makes it possible to adjust the interaction strength on a fine level, allowing for additional control over assembly formation.

Once the data-enabled optimization procedures are implemented, it will be possible to create assemblies with desired properties for particular tasks, which will represent a significant advance in functional materials design. Moreover, the general approach is not specific to a particular property and could be adapted for any application involving similar donor/acceptor building blocks.

Controlling material assembly will enable vast new functionalities and catalyze transformative advances across a number of fields. Concurrent with the research, the teaching and outreach activities will educate the next generation of scientists on functional materials and engage a diverse student population on STEM topics, including historically underrepresented groups and those with learning disabilities.

This project addresses the basic science knowledge gap associated with directed assembly, and it is consistent with the NSF mission of supporting fundamental research, tightly integrated with science education and community outreach.

The overarching objective of this proposal is to develop molecular assemblies, bound by halogen bonds and other noncovalent interactions, with characteristics that facilitate more efficient chemical and environmental processes. It is hypothesized that tuning the strength and nature of halogen bonding between the molecular components will enable the ability to direct assembly formation and tailor the structural, electronic, and optical properties of the system.

Modeling studies will guide bottom-up materials design using molecular-level building blocks to generate supramolecular structures and control their function. Molecular quantum chemistry and atomistic simulation will be used to produce a predictive formalism that is well suited for future integration of advanced optimization algorithms. Specific aims include the following: (1) Characterize the molecular properties of halogen bond donors and acceptors to ascertain the effects of geometry, atomic substitution, and functionalization; (2) Assess stability, quantify halogen bonding strength, and determine the nature of noncovalent interactions in donor/acceptor units; and (3) Direct the assembly of extended two- and three-dimensional halogen bonded networks with tailored structural, electronic, and optical properties.

These aims align with the overarching objective of directed assembly of supramolecular structures with desired characteristics, while concurrently addressing research that enables more efficient chemical processes, improves environmental sustainability, and advances the design of functional materials with tailored properties. These studies will provide predictive capabilities for a particular class of donor/acceptor networks; however, the underlying principles of directed assembly are highly relevant to other materials and biological systems.

Thus, the proposed research is of great fundamental importance and impactful to many scientific fields in chemistry, biology, physics, and materials science.

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.