Application of Solid-State Vibrational Circular Dichroism for Intercalation Compounds of Layered Double Hydroxide and Amino Acids: Conformation of an Intercalated Phenylalanine

Abstract

Abstract Solid-state vibrational circular dichroism (SD-VCD) spectra were measured for the intercalation compounds of layered double hydroxide (LDH) and d- or l-phenylalanine (d- or l-Phe). The investigated LDH was composed of Zn(II) and Al(III) in 2:1 molar ratio. For comparison, the SD-VCD spectra were recorded for enantiopure crystalline samples of Phe. The measured spectra were analyzed with the help of a theoretical simulation calculated by the Gaussian16 program. It was concluded that Phe formed a tetramer in the crystalline state, forming intermolecular hydrogen bonds between –COO− and –NH3+ groups. In the intercalated states, the neighboring Phe molecules oriented vertically to the layer surface in an anti-parallel fashion, forming their –COO− groups hydrogen bonded individually with the OH groups on the surface of LDH. The results demonstrated the utility of the SD-VCD method for obtaining the detailed conformation of a molecule within an inorganic host.