Rationalizing hydrogen bond solvation with Kamlet-Taft LSER and molecular torsion balances

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Supramolecular Chemistry

Background:

• Hydrogen bonds are crucial for molecular structure and function.
• Quantifying weak intramolecular hydrogen bond strength is challenging.
• Solvent effects significantly influence hydrogen bond characteristics.

Purpose of the Study:

• To quantify the strength of weak intramolecular hydrogen bonds.
• To analyze the impact of solvation on hydrogen bond strength.
• To develop a predictive model for hydrogen bond behavior.

Main Methods:

• Utilized molecular torsion balances to measure hydrogen bond strength.
• Applied Kamlet-Taft's Linear Solvation Energy Relationship (LSER).
• Performed linear regression analysis to correlate hydrogen bond strength with solvent parameters.

Main Results:

• Hydrogen bond strength varied from -0.99 to +1.00 kcal mol⁻¹ due to solvation.
• Developed a predictive equation: ΔG_H-Bond = -1.37 - 0.14α + 2.10β + 0.74(π* - 0.38δ) kcal mol⁻¹ (R² = 0.99).
• The solvent's hydrogen-bond donor parameter (β) was the dominant factor influencing hydrogen bond strength.

Conclusions:

• Solvation effects, particularly electrostatic interactions, are critical for hydrogen bond strength.
• Nonspecific solvent interactions also play a significant role.
• The developed model provides a tool for predicting and controlling hydrogen bond efficiency.