Redox-Responsive H-Bonding Systems for Supramolecular Applications

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professor Diane Smith of San Diego State University will be exploring new methods to selectively control the strength of interactions between molecules using electron transfer combined with proton transfer. The molecules involved can be thought of as synthetic relatives of the natural base pairs that link together the two strands of the DNA double helix.

These natural base pairs link together in a highly specific fashion, a feature necessary for the reliable transfer of genetic information. In the synthetic versions under investigation, the linkages also are highly specific, but, unlike their natural cousins, the strength of the linkage should be switchable, reversibly going from weak to strong by using electron transfer to induce proton transfer between base pairs.

The resulting highly selective ON/OFF binding may find application in a variety of smart materials and sensing systems, as well as molecular devices and machines. In addition, the research itself, which involves a variety of skill sets, will provide an excellent, well-rounded education to the diverse group of students involved, including graduate, undergraduate and high school students, many of whom are from groups underrepresented in science.

More specifically, the primary goal of this project is to explore the generality and test the limits of using electron transfer to greatly alter binding strength in hydrogen bond (H-bond) heterodimers (base pairs) by inducing proton transfer across a H-bond. This changes the nature of the secondary H-bonds, which are well-known to strongly affect overall binding strength.

In Aim 1 of this project, Professor Smith and her students aim to significantly expand upon a previous result in which a 10^5-fold increase in binding strength in a 3 H-bond dimer is observed by using the same reduction-based redox couple to create 4 and 6 H-bond heterodimers and by exploring the use of 2 different oxidation-based couples to create new highly redox-responsive 3 H-bond dimers. Furthermore, fundamental issues governing the strength of the effect will be explored with simple 2 H-bond systems in a sub-project specifically designed for undergraduates, and, in Aim 2, aided by high school interns, the team will determine the ease with which the solution chemistry can be translated to surfaces by attaching the electro-active component to electrode surfaces.

Aim 3 will investigate whether H-bond dimers with very large changes in binding strength between oxidation states can be used to advantage for the construction of highly redox-responsive supramolecular polymers.

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.