Theoretical ab Initio Study on Cooperativity Effects between Nitro π-hole and Halogen Bonding Interactions.

Area of Science:

• Computational Chemistry
• Supramolecular Chemistry
• Organic Chemistry

Background:

• Nitroarenes possess distinct π-holes, one on the nitro group and another on the aromatic ring.
• Halogen bonding (XB) is a significant non-covalent interaction involving electrophilic regions of halogen atoms.

Purpose of the Study:

• To investigate the cooperative effects between nitroarene π-holes and halogen bonding.
• To analyze the energetic and geometric interplay of these coexisting interactions.

Main Methods:

• Quantum chemical calculations using RI-MP2/def2-TZVPD level of theory.
• Molecular Electrostatic Potential (MEP) surface calculations.
• Atoms in Molecules (AIM) theory for interaction characterization.
• Natural Bond Orbital (NBO) and Non-covalent Interaction (NCIPlot) analyses.
• Validation with experimental data from the Cambridge Structural Database (CSD).

Main Results:

• Demonstrated remarkable cooperativity when π-hole and XB interactions coexist in nitroarene complexes.
• Identified the nitro group's π-hole as more positive and influential in the interplay.
• Quantified interaction strength and charge density variations using AIM and MEP.
• Observed mutual influence on interaction strength and geometry.

Conclusions:

• The interplay between π-holes and halogen bonding in nitroarenes leads to significant cooperative effects.
• Computational methods employed are effective in characterizing these mutual influences.
• Experimental evidence supports the theoretical findings on interaction cooperativity.