Structure Simulation and Host–Guest Interaction of Histidine-Intercalated Hydrotalcite–Montmorillonite Complex

Abstract

The structures of histidine intercalated hydrotalcite–montmorillonite complex (His–LDHs–MMT) were studied using the DMol3 code, GGA/PW91 function, and DND basis set of the density functional theory (DFT). The geometries of His–LDHs–MMT were optimized, and their electronic properties were calculated. The results showed that the structure of the complex can be seen as that the quaternary ammonium group of histidine was adsorbed on the oxygen of MMT lamella, and its oxygen on the carboxylic acid anion was combined with the hydrogen atoms of the LDHs lamella. It was determined that the interaction mainly consisted in hydrogen bonding and electrostatic force. The average binding energies per histidine of His–LDHs and His–MMT were about −65.89 and −78.44 kcal/mol, respectively. The density of states of the complexes showed that the 2p orbitals of oxygen were dominant, and the 1s orbit of hydrogen near the Fermi level indicate the formation of hydrogen bonds in the complex. The charge density data displayed the density field of histidine carboxylic acid anion overlapped with that of hydrotalcite layer, indicating that a strong hydrogen bond interaction existed between histidine and hydrotalcite layer. The analysis of the electrostatic potential of complex indicated that the electrostatic interaction between histidine and MMT is obviously stronger than that of LDHs. The simulated XRD spectra showed the special diffraction peaks of LDHs and MMT layer in the complex.