Hydrogen bond networks in gas-phase complex anions

Area of Science:

• Physical Chemistry
• Supramolecular Chemistry
• Chemical Physics

Background:

• Hydrogen bond networks (HBNs) play vital roles in natural systems.
• Isolating HBNs from complex environments for study remains challenging.

Purpose of the Study:

• To investigate HBNs within gas-phase complex anions formed by alpha-cyclodextrin (α-CD) and four benzoic acids (RBAs).
• To establish a simplified model system for studying HBN characteristics.

Main Methods:

• Electrospray ionization (ESI) to extract complex anions from solution.
• Collision-induced dissociation (CID) to probe transition dynamics.
• Computational analysis to explain dissociation pathways and HBN stability.

Main Results:

• The dominant dissociation pathway observed was the generation of deprotonated α-CD and neutral RBAs.
• Complex anions formed with more acidic RBAs demonstrated enhanced stability.
• Cooperative stretching dynamics of intramolecular and intermolecular hydrogen bonds (HBs) explained the dissociation patterns.
• Evidence suggests the presence of rare low barrier hydrogen bonds (LBHBs).

Conclusions:

• Gas-phase complex anions of α-CD and RBAs serve as an accessible model for HBN research.
• The stability of these complexes correlates with the acidity of the RBAs.
• The study elucidates the dynamics of HBNs, including potential LBHBs, in a controlled system.