The structure, vibrational spectra and nonlinear optical properties of the l-lysine × tartaric acid complex—Theoretical studies

The room temperature X-ray studies of l-lysine × tartaric acid complex are not unambiguous. The disorder of three atoms of carbon in l-lysine molecule is observed. These X-ray studies are ambiguous. The theoretical geometry study performed by DFT methods explain the most doubts which are connected with crystallographic measurements.The theoretical vibrational frequencies and potential energy distribution (PED) of l-lysine × tartaric acid were calculated by B3LYP method. The calculated frequencies were compared with experimental measured IR spectra. The complete assignment of the bands has been made on the basis of the calculated PED.The restricted Hartee–Fock (RHF) methods were used for calculation of the hyperpolarizability for investigated compound. The theoretical results are compared with experimental value of β.