Hydrogen-bonding network in anhydrous chitosan from neutron crystallography and periodic density functional theory calculations

• Published in: Carbohydrate polymers Vol. 207; pp. 211 - 217
• Main Authors: Ogawa, Yu, Naito, Philip-Kunio, Nishiyama, Yoshiharu
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2019; Elsevier
• Subjects: Animals; Brachyura - chemistry; Cellulose - chemistry; Chemical Sciences; Chitosan; Chitosan - chemistry; Cristallography; Density Functional Theory; Hydrogen bond; Hydrogen Bonding; Models, Chemical; Molecular Structure; Neutron crystallography; Neutron Diffraction; Periodic density functional calculation; Polymers; Neutron crystallography; Chitosan; Periodic density functional calculation; Hydrogen bond
• ISSN: 0144-8617; 1879-1344
• DOI: 10.1016/j.carbpol.2018.11.042

•The hydrogen bonding network in anhydrous chitosan was explicitly determined.•The hydrogen positions were resolved using neutron diffraction and DFT calculation.•Strength and flexibility of the hydrogen bonds were studied using DFT calculation.•The hydroxyl groups act as HB donors while the amino group is a strong HB acceptor. The hydrogen-bonding network in anhydrous chitosan crystal was studied using a combination of neutron crystallography and quantum chemical calculation. The locations of the hydroxyl hydrogen were directly resolved using Fourier omit maps applied to neutron diffraction data, whereas the amino hydrogen atoms were determined based on geometrical optimization using periodic density functional theory (DFT) calculation. Energy optimization of the hydrogen positions based on DFT calculation allowed the measurement of the hydrogen-bond energies. In the chitosan crystal, the hydroxyl groups mostly play a role as hydrogen-bond donors while the amino moiety behaves as a strong acceptor but a poor donor.