Hydrogen bonds of a water molecule in the second coordination sphere of amino acid metal complexes: influence of amino acid types on different complex geometries

Abstract

Quantum chemical calculations at the M06L-GD3/def2-TZVPP level were done to investigate hydrogen bonds between amino acid metal complexes and a free water molecule. Octahedral nickel(II) and square planar palladium(II) complexes of glycine, cysteine, phenylalanine, and serine with different charges of metal complexes (+1, 0, and −1) were investigated. The following hydrogen bonds were considered: NH/O (amino acid is a H-donor), O1/HO (coordinated O1 oxygen from amino acid is a H-acceptor), and O2/HO (non-coordinated O2 oxygen from amino acid is a H-acceptor). Amino acid type has a small influence on interaction energies, both for octahedral nickel(II) and square planar palladium(II) complexes. The influence is the largest for NH/O and the smallest for O2/HO hydrogen bonds. For NH/O interaction, palladium(II) complexes showed stronger hydrogen bonds than nickel(II), up to −11.8 kcal mol⁻¹ for singly positively charged complexes. Nickel(II) complexes demonstrated higher O1/HO hydrogen bond strength than palladium(II) with interaction energies up to −8.9 kcal mol⁻¹ for singly negative complexes. With up to −9.0 kcal mol⁻¹ interaction energy for singly negative complexes, O2/HO interactions were also stronger for nickel(II) complexes than palladium(II).

Keywords:

• Non-covalent interactions
• hydrogen bonds
• amino acids
• metal complexes
• density functional theory (DFT)

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research is funded by the Ministry of Education and Ministry of Science, Technological Development and Innovation, Republic of Serbia, Contract numbers: 451-03-47/2023-01/200168 and 451-03-47/2023-01/200288. The high-performance computers were provided by the IT Research Computing Group at Texas A&M University in Qatar, which is founded by Qatar Foundation for Education, Science and Community Development.