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Metal-Centered Noncovalent Interactions: A Comparative Insight into π-Hole- and σ-Hole-Directed Bonds
Sanskruti Ramprasad Mishra1, Dipankar Sutradhar1
1Chemistry Division, School of Advanced Sciences and Languages, VIT Bhopal University, Bhopal, India.
Summary
This study compares π-hole and σ-hole interactions in metal halides with pyridines. Beryllium chloride (BeCl2) shows the strongest interaction, while MoOF4 exhibits unique orbital interactions.
Area of Science:
- Computational Chemistry
- Inorganic Chemistry
- Supramolecular Chemistry
Background:
- Non-covalent interactions are crucial in chemistry and biology.
- π-holes and σ-holes are regions of positive electrostatic potential that can engage in attractive interactions.
Purpose of the Study:
- To investigate and compare π-hole-driven interactions of BeCl2, MgCl2, and HgCl2 with pyridines.
- To examine σ-hole-directed interactions of MoOF4 and OsO4 with pyridines.
- To analyze the factors governing the strength and nature of these interactions.
Main Methods:
- Quantum chemical calculations were employed to study the interactions.
- Atom-in-jellium (AIM) analysis was used to characterize the nature of the bonds.
- Natural Bond Orbital (NBO) analysis was performed to understand orbital interactions and hyperconjugation.
Main Results:
- BeCl2 exhibited the strongest π-hole interaction (Be…N), followed by MgCl2 (Mg…N) and HgCl2 (Hg…N).
- MoOF4 showed a stronger σ-hole interaction (Mo…N) than OsO4 (Os…N).
- Binding energies correlated linearly with Lewis acid deformation energies; interactions were mostly covalent, except for MgCl2 (electrostatic).
Conclusions:
- The binding energy trend is BeCl2 > MgCl2 > MoOF4 > HgCl2 > OsO4.
- NBO analysis revealed complex interplay of hyperconjugation and exchange contributions.
- MoOF4 displayed unique LP(N)→LP*(Mo) orbital interaction beyond typical σ-hole bonding.
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