Exploring the (H2C═PH2)(+):N-Base Potential Surfaces: Complexes Stabilized by Pnicogen, Hydrogen, and Tetrel Bonds

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Intermolecular Interactions

Background:

• The cation (H2C═PH2)(+) is investigated for its potential to form various non-covalent interactions.
• Nitrogen bases with sp-hybridized atoms are chosen to probe diverse bonding scenarios.

Purpose of the Study:

• To determine the structures, binding energies, and bonding properties of complexes formed between (H2C═PH2)(+) and sp-hybridized nitrogen bases.
• To analyze four unique equilibrium structures: pnicogen-bonded (ZB-π, ZB-σ), hydrogen-bonded (HB), and tetrel-bonded (TB) complexes.
• To investigate the relationship between binding energies, intermolecular distances, and charge-transfer energies.

Main Methods:

• Ab initio MP2/aug'-cc-pVTZ calculations were employed to model the molecular complexes.
• Analysis included structural determination, binding energy calculations, and spin-spin coupling constants.

Main Results:

• Four distinct bonding types (pnicogen, hydrogen, tetrel) were identified for the (H2C═PH2)(+):N-base complexes.
• Binding energies generally decrease with weaker bases (N2 < NCCN < NCF < NCH < NCCl < NP < NCCH3) and follow the order ZB-π > HB > ZB-σ > TB for a given base.
• Exponential relationships were observed between binding energies and distances for ZB-π, HB, and ZB-σ interactions, with charge-transfer energies also showing exponential dependence.

Conclusions:

• The study elucidates the nature and strength of various intermolecular interactions involving the phosphonium cation.
• Pnicogen and hydrogen bonds are significantly stronger and more distance-dependent than tetrel bonds in these systems.
• Charge-transfer plays a crucial role in stabilizing these complexes.