Theoretical study on stabilities of multiple hydrogen bonded dimers

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Interactions

Background:

• Multiple hydrogen bonded (MHB) complexes are fundamental in various chemical and biological systems.
• Understanding the factors governing the stability of these complexes is crucial for predicting their behavior and designing new molecular architectures.

Purpose of the Study:

• To systematically investigate the energetic properties and stability of self-constituted multiple hydrogen bonded (MHB) complexes.
• To elucidate the roles of charge transfer, cooperativity, and correlation energy in determining the stability of MHB complexes.

Main Methods:

• Density Functional Theory (DFT) calculations using the PBE1PBE functional with a 6-31G** basis set.
• Morokuma energy decomposition analysis using Hartree-Fock (HF) with a 6-31G** basis set.
• Second-order Møller-Plesset perturbation theory (MP2) calculations with 6-31G** and 6-311++G** basis sets.

Main Results:

• For doubly hydrogen bonded (DHB) complexes, interaction energy and stability increase with charge transfer energy.
• In quadruple hydrogen bonded (QHB) complexes, cooperativity is the dominant factor for stability, correlating directly with interaction energy.
• Correlation energy, primarily dispersive energy, exhibits cooperative effects in MHB dimers, being positive for M-aadd and generally negative for others.

Conclusions:

• Charge transfer is a significant contributor to the stability of DHB complexes.
• Cooperativity is the primary determinant of stability in QHB complexes, highlighting the synergistic effects of multiple hydrogen bonds.
• Correlation energy, particularly dispersive interactions, plays a vital role in the overall stability and cooperative phenomena within MHB systems.