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Stable three-center hydrogen bonding in a partially rigidified structure
1Department of Chemistry, Natural Sciences Complex, State University of New York, Buffalo 14260, USA. bgong@chem.buffalo.edu
Chemistry (Weinheim an Der Bergstrasse, Germany)
|November 7, 2001
Summary
This study reveals the first evidence of positive cooperativity in a three-center hydrogen bond within diaryl amide molecules. This finding enhances understanding of intramolecular hydrogen bonding and stable structure design.
Area of Science:
- Organic Chemistry
- Computational Chemistry
- Structural Chemistry
Background:
- Intramolecular hydrogen bonds play a crucial role in stabilizing molecular structures.
- Three-center hydrogen bonds are less understood compared to traditional two-center bonds.
- Diaryl amides offer a scaffold for investigating complex hydrogen bonding interactions.
Purpose of the Study:
- To investigate the nature and stability of a three-center hydrogen bond in a diaryl amide system.
- To determine if positive cooperativity exists between the components of the three-center hydrogen bond.
- To provide insights into designing molecules with stable folded structures.
Main Methods:
- Infrared (IR) spectroscopy
- Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy
- X-ray crystallography
- Ab initio computational calculations
Main Results:
- The study identified a three-center hydrogen bond in diaryl amide 1.
- Experimental and computational data confirmed positive cooperativity between the two-center components, enhancing bond stability.
- Substituents not participating in hydrogen bonding showed minimal impact on bond strength.
- This represents the first documented three-center hydrogen-bonding system exhibiting positive cooperativity.
Conclusions:
- The three-center hydrogen bond in diaryl amide 1 exhibits positive cooperativity, a novel finding.
- The stability of this hydrogen bond is attributed to the reinforcing interaction between its components.
- The findings offer a reliable motif for the rational design of stably folded molecular structures.