Ab initio calculations on halogen-bonded complexes and comparison with density functional methods.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Molecular Interactions

Background:

• Halogen bonding is a significant non-covalent interaction.
• Accurate theoretical prediction of these interactions is crucial for understanding molecular assembly and reactivity.

Purpose of the Study:

• To systematically investigate dimeric complexes formed between halocarbons and electron donors.
• To evaluate the accuracy of various computational methods for predicting halogen bond strengths.

Main Methods:

• Ab initio methods, including Moller-Plesset second-order perturbation (MP2) and coupled cluster with single, double, and noniterative triple excitations [CCSD(T)].
• Geometry optimizations using the aug-cc-pVDZ basis set.
• Extrapolation of binding energies to the complete basis set (CBS) limit.

Main Results:

• CCSD(T) calculations at the CBS limit yielded binding energies ranging from -0.89 to -4.38 kcal/mol for the studied halogen-bonded complexes.
• Density functional theory (DFT) methods were compared against high-level ab initio results.
• PBEKCIS, B97-1, and MPWLYP functionals demonstrated accuracy comparable to computationally intensive ab initio methods.

Conclusions:

• The study provides reliable binding energy data for halogen-bonded complexes.
• Selected DFT functionals offer a computationally efficient alternative for studying halogen bonding with high accuracy.