The Stability of Hydrogen‐Bonded Ion‐Pair Complex Unexpectedly Increases with Increasing Solvent Polarity

• DOI: 10.1002/ange.202403218
• Publication Date: 2024-03-18T09:58:35Z
• Authors: Debashree Manna; Rabindranath Lo; Jaroslav Vacek; Vijay Madhav Miri...; Petr Bouř; Tao Wu; Zuzana Osifová; Dana Nachtigallová; Martin Dračinský; Pavel Hobza
• Keywords: Polarity (international relations); Solvent polarity

Abstract The generally observed decrease of the electrostatic energy in complex with increasing solvent polarity has led to assumption that stability complexes ion‐pair hydrogen bonds decreases polarity. Besides, smaller solvent‐accessible surface area (SASA) comparison isolated subsystems results a solvation latter, leading destabilization compared gas phase. In our study, which combines Nuclear Magnetic Resonance, Infrared Spectroscopy experiments, quantum chemical calculations, and molecular dynamics (MD) simulations, we question general validity this statement. We demonstrate binding free hydrogen‐bonded between 2‐fluoropropionic acid n ‐butylamine (CH 3 CHFCOO − …NH But + ) increases increased This phenomenon is rationalized by substantial charge transfer constitute complex. unexpected finding introduces new perspective understanding dynamics, emphasizing interplay within systems.