Modulation of stacking interactions by transition-metal coordination: ab initio benchmark studies

Area of Science:

• Computational Chemistry
• Organometallic Chemistry
• Supramolecular Chemistry

Background:

• Understanding non-covalent interactions of aromatic rings is crucial in chemistry.
• The influence of transition-metal coordination on these interactions is not fully elucidated.
• Aromatic rings play vital roles in biological systems and materials science.

Purpose of the Study:

• To investigate the effects of transition-metal coordination on C-H···pi and pi-pi stacking interactions.
• To quantify changes in hydrogen bond donating and accepting abilities of coordinated aromatic rings.
• To assess the strength of pi-pi stacking in metal-arene complexes.

Main Methods:

• Ab initio calculations were performed on model complexes: ferrocene and chromium benzene tricarbonyl.
• High-level theoretical methods, including MP2 and CCSD(T) with basis set extrapolation, were employed for benchmark data.
• Energy partitioning was used to analyze interaction components.

Main Results:

• Coordinated aromatic rings are weaker hydrogen bond acceptors but stronger donors compared to free rings.
• Pi-pi stacking interactions are enhanced in metal-coordinated systems, notably in chromium benzene tricarbonyl.
• Dispersion interactions between metal d and benzene pi orbitals significantly contribute to enhanced pi-pi stacking.

Conclusions:

• Transition-metal coordination significantly modulates the non-covalent interactions of aromatic rings.
• The findings provide insights into the electronic and structural properties of organometallic complexes.
• The study validates computational methods for studying such systems, highlighting the performance of spin-component scaled MP2 and limitations of certain density functionals.