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Unique O═N...O Pnicogen Interactions in Nitromethane Dimers: Evidence Using Matrix Isolation Infrared Spectroscopy
Swaroop Chandra1,2, Nandalal Mahapatra1,2, Nagarajan Ramanathan1,2
1Materials Chemistry and Metal Fuel Cycle Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102, Tamilnadu, India.
The Journal of Physical Chemistry. A
|May 24, 2022
Summary
Nitromethane homodimers exhibit O═N...O pnicogen bonding, not just dispersion forces or weak hydrogen bonds. This specific bonding dictates their geometry, even at larger intermolecular distances observed in liquid states.
Area of Science:
- Computational Chemistry
- Spectroscopy
- Chemical Physics
Background:
- Previous studies suggested dispersion forces or weak hydrogen bonds govern nitromethane homodimer interactions.
- Assumptions about intermolecular interactions were influenced by observed spectral invariance and larger separations in liquid phases.
Purpose of the Study:
- To re-evaluate the intermolecular interactions within nitromethane homodimers.
- To provide concrete evidence for the dominant bonding interactions responsible for dimer geometry.
Main Methods:
- Ab initio and density functional theory calculations.
- Matrix isolation infrared spectroscopy (Ne and Ar matrices).
- Quantum theory of atoms in molecules (QTAIM), natural bond orbital (NBO) analysis, energy decomposition, electrostatic potential mapping, and noncovalent interaction (NCI) analyses.
Main Results:
- Presented concrete evidence for the prevalence of O═N...O pnicogen bonding in nitromethane homodimers.
- Demonstrated that pnicogen bonds are primarily responsible for the characteristic homodimer geometry.
- Affirmed the presence of hydrogen and pnicogen bonds even at larger intermolecular separations.
Conclusions:
- Pnicogen bonding plays a crucial role in stabilizing nitromethane homodimers.
- The findings challenge previous assumptions about the nature and strength of intermolecular interactions in nitromethane.
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