On the Nature of Blueshifting Hydrogen Bonds. Issue 27 (26th May 2014)

• Record Type: Journal Article
• Authors: Mo, Yirong; Wang, Changwei; Guan, Liangyu; Braïda, Benoît; Hiberty, Philippe C.; Wu, Wei
• Is Part Of: Chemistry. Volume 20:Issue 27(2014)
• Page Start: 8444
• Page End: 8452
• Publication Date: 2014-05-26
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201402189
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The block‐localized wave function (BLW) method can derive the energetic, geometrical, and spectral changes with the deactivation of electron delocalization, and thus provide a unique way to elucidate the origin of improper, blueshifting hydrogen bonds versus proper, redshifting hydrogen bonds. A detailed analysis of the interactions of F<sub>3</sub>CH with NH<sub>3</sub> and OH<sub>2</sub> shows that blueshifting is a long‐range phenomenon. Since among the various energy components contributing to hydrogen bonds, only the electrostatic interaction has long‐range characteristics, we conclude that the contraction and blueshifting of a hydrogen bond is largely caused by electrostatic interactions. On the other hand, lengthening and redshifting is primarily due to the short‐range <italic>n</italic>(Y)→σ*(XH) hyperconjugation. The competition between these two opposing factors determines the final frequency change direction, for example, redshifting in F<sub>3</sub>CH<bold>⋅⋅⋅</bold>NH<sub>3</sub> and blueshifting in F<sub>3</sub>CH<bold>⋅⋅⋅</bold>OH<sub>2</sub>. This mechanism works well in the series F<sub><italic>n</italic></sub>Cl<sub>3−<italic>n</italic></sub>CH<bold>⋅⋅⋅</bold>Y (<italic>n</italic>=0–3, Y=NH<sub>3</sub>, OH<sub>2</sub>, SH<sub>2</sub>) and other systems. One exception is the complex of water and benzene. We observe the lengthening and redshifting of the OH bond of water even with the electron transfer between benzene and water completely quenched. A distance‐dependent analysis for this system reveals that the long‐range electrostatic interaction is again responsible for the initial lengthening and redshifting.</p> </abstract>