H-Bond Network in Amino Acid Cocrystals with H2O or H2O2. The DFT Study of Serine–H2O and Serine–H2O2

• Published in: The journal of physical chemistry. A, Molecules, spectroscopy, kinetics, environment, & general theory Vol. 115; no. 46; pp. 13657 - 13663
• Main Authors: Vener, Mikhail V, Medvedev, Alexander G, Churakov, Andrei V, Prikhodchenko, Petr V, Tripol’skaya, Tatiana A, Lev, Ovadia
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 24-11-2011
• Subjects: A: Molecular Structure, Quantum Chemistry, General Theory; Amino Acids - chemistry; Crystallization; Hydrogen Bonding; Hydrogen Peroxide - chemistry; Quantum Theory; Serine - chemistry; Water - chemistry
• ISSN: 1089-5639; 1520-5215
• DOI: 10.1021/jp207899z

The structure, IR spectrum, and H-bond network in the serine–H2O and serine–H2O2 crystals were studied using DFT computations with periodic boundary conditions. Two different basis sets were used: the all-electron Gaussian-type orbital basis set and the plane wave basis set. Computed frequencies of the IR-active vibrations of the titled crystals are quite different in the range of 10–100 cm–1. Harmonic approximation fails to reproduce IR active bands in the 2500–2800 frequency region of serine–H2O and serine–H2O2. The bands around 2500 and 2700 cm–1 do exist in the anharmonic IR spectra and are caused by the first overtone of the OH bending vibrations of H2O and a combination vibration of the symmetric and asymmetric bendings of H2O2. The quantum-topological analysis of the crystalline electron density enables us to describe quantitatively the H-bond network. It is much more complex in the title crystals than in a serine crystal. Appearance of water leads to an increase of the energy of the amino acid–amino acid interactions, up to ∼50 kJ/mol. The energy of the amino acid–water H-bonds is ∼30 kJ/mol. The H2O/H2O2 substitution does not change the H-bond network; however, the energy of the amino acid–H2O2 contacts increases up to 60 kJ/mol. This is caused by the fact that H2O2 is a much better proton donor than H2O in the title crystals.