Hydrogen Bond

Hydrogen bonding is one of the most fundamental non-covalent interactions in chemistry, playing a key role in molecular recognition, solvation, catalysis, and biological structure. Early in my career, I focused on understanding hydrogen bond cooperativity, resonance-assisted hydrogen bonding, and their interplay with electronic delocalization and aromaticity. Using real-space analyses and energy decomposition methods, I explored how subtle changes in geometry or electronic structure modulate hydrogen bond strength and function. These studies laid the foundation for my broader interest in non-covalent interactions and their role in chemical reactivity and molecular design.

Hydrogen Bonding 102: Cooperativity and Anticooperativity in the Water Hexamer

In this work, we took a closer look at one of the most iconic systems in hydrogen bonding studies: the water hexamer. While it’s often used as a model system, we wanted to go beyond the usual descriptions and quantify how each hydrogen bond is influenced by its neighbors. Using the Interacting Quantum Atoms (IQA) method, we dissected individual interactions and revealed a more nuanced picture, one where both cooperativity and anticooperativity emerge, depending on the geometry and bonding context.

This study helped reinforce the idea that hydrogen bonds in clusters don’t behave independently. They respond to each other in subtle but measurable ways. It also showed how real-space energy decomposition methods can offer detailed insight into interaction patterns that are often generalized or oversimplified.

Hydrogen Bonding 201: The Nature of Resonance Assisted Hydrogen Bonds

In this paper, we tackled the concept of resonance assisted hydrogen bonding, a term often used to describe unusually strong hydrogen bonds influenced by electronic delocalization. But we wanted to move past qualitative ideas and see what the numbers actually say.

Using a combination of Interacting Quantum Atoms (IQA) and Quantum Theory of Atoms in Molecules (QTAIM), we analyzed how resonance affects the strength and character of hydrogen bonds in a series of organic systems. What we found is that the situation is more complex than the standard textbook narrative. While resonance can enhance hydrogen bonding, the effect depends on subtle shifts in charge distribution and energy balance, not just on having a conjugated system nearby.

This work helped clarify what resonance assistance really means from a quantum chemical point of view, and highlighted the value of real space methods for dissecting the underlying physics of bonding.