Comprehensive Analysis of Deuterium Isotope Effects on Ionic H₃O^+…π Interactions Using Multi-Component Quantum...

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• Proton and deuteron quantum effects influence molecular interactions.
• Hydronium ion (H3O+) complexes with unsaturated hydrocarbons exhibit O-H(D)...π bonding.
• Understanding isotope effects is crucial for accurate molecular modeling.

Purpose of the Study:

• To analyze deuterium isotope effects on interaction energies and geometries.
• To investigate H3O+(D3O+)...alkene and H3O+(D3O+)...alkyne complexes.
• To elucidate the role of nuclear quantum effects in these systems.

Main Methods:

• Multi-component molecular orbital (MC-MP2) method incorporating nuclear quantum effects.
• MP2 level of theory for electronic structure calculations.
• Natural energy decomposition analysis (NEDA) for interaction energy components.

Main Results:

• Deuterium substitution (D3O+) reduced interaction energies compared to H3O+.
• Geometrical parameters of the complexes were altered by deuterium replacement.
• A strong correlation was found between H/D isotope effects on distances and energy components.

Conclusions:

• Nuclear quantum effects, particularly H/D isotope effects, significantly influence non-covalent interactions.
• MC-MP2 calculations accurately capture these subtle effects.
• Findings provide insights into the behavior of protonated and deuterated species in chemical systems.