Cooperativity in intramolecular bifurcated hydrogen bonds: an ab initio study

Area of Science:

• Computational Chemistry
• Molecular Modeling
• Supramolecular Chemistry

Background:

• Hydrogen bonds are crucial in molecular interactions.
• Bifurcated hydrogen bonds involve a single donor or acceptor interacting with multiple atoms.
• Investigating cooperativity in hydrogen bonds can reveal unique molecular properties.

Purpose of the Study:

• To investigate the cooperative effects in pairs of bifurcated hydrogen bonds within the same molecule.
• To explore the H...A...H and A...H...A hydrogen bonding types using model systems.
• To analyze the reinforcement between simultaneously present intramolecular bifurcated hydrogen bonds.

Main Methods:

• Molecular orbital calculations
• Density functional theory (DFT) computations
• Analysis of di- and tetrasubstituted anthraquinone, dihydrophenazine, and acridone derivatives.

Main Results:

• Confirmed significant reinforcement between two intramolecular bifurcated hydrogen bonds.
• Demonstrated cooperativity in both H...A...H and A...H...A hydrogen bonding motifs.
• Identified specific roles of C=O, OH, and N-H groups as donors and acceptors in these interactions.

Conclusions:

• Intramolecular bifurcated hydrogen bonds exhibit strong cooperative effects.
• The simultaneous presence of these bonds leads to mutual reinforcement.
• This study provides insights into the complex nature of hydrogen bonding in organic molecules.