Complexes with N-H(+)-P hydrogen bonds: structures, binding energies, and spin-spin coupling constants.

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Chemical Physics

Background:

• Proton-bound complexes are crucial in chemical and biological systems.
• Understanding hydrogen bond dynamics and proton transfer is fundamental.
• N-H+-P hydrogen bonds represent a specific class with unique properties.

Purpose of the Study:

• To determine the structures and binding energies of N-H+-P hydrogen-bonded complexes.
• To investigate the proton-transfer coordinate in these systems.
• To analyze spin-spin coupling constants across these hydrogen bonds.

Main Methods:

• Ab-initio MP2/aug'-cc-pVTZ calculations for structures and binding energies.
• Equation-of-motion coupled cluster singles and doubles (EOM-CCSD) for spin-spin couplings.
• Analysis of potential energy surfaces and correlation of coupling constants with distances.

Main Results:

• Double minima observed when protonation energy difference is < 4 kcal/mol.
• Nitrogen-donor isomer is energetically favored with greater binding energy.
• Two-bond N-P coupling constants correlate with N-P distances.
• One-bond couplings correlate with distances for N-H+...P but not P-H+...N bonds.
• Negative (1h)K(H-N) and (1h)K(H-P) values confirm traditional hydrogen bonds.

Conclusions:

• Proton transfer in N-H+-P systems is sensitive to base properties.
• Spin-spin coupling constants offer valuable structural and electronic information.
• These findings contribute to the understanding of hydrogen bonding in diverse chemical environments.