Are there preferable conformations of the tryptammonium cation in the solid state? Crystal structure and solid-state linear polarized IR-spectroscopic study of tryptammonium hydrogentartarate

Abstract

Tryptammonium hydrogentartarate (1) crystallizes in the orthorhombic space group P2 1 2 1 2 1 and exhibits a crystal structure consisting of the tryptammonium cation, hydrogentartarate anion and a solvent methanol. The cations and anions are joined into a 3D network by intermolecular NHÁÁÁOH(CH 3 ) and NH 3 ÁÁÁO (tart) bonds with lengths of 2.998, 2.772, 2.902, and 2.847 Å , respectively. Hydrogentartarate anions are themselves connected by strong intermolecular OÁÁÁH-O hydrogen bonds with lengths of 2.481 Å into infinite chains. The anions also participate in moderate hydrogen bonding with solvent methanol molecules of the (tart) OÁÁÁO(CH 3 ) type with bond lengths of 2.736 and 2.762 Å ). The conformational preference of the tryptammonium cation is discussed by comparing the results with the data for other crystallographically determined structures of salts. Quantum chemical calculations at (density functional theory) DFT (B3LYP) level of theory and 6-311++G** basis set are performed for the interacting system tryptammonium cation/H 2 O with a view to predicting the geometry of the most stable conformer. The optical properties of tryptammonium hydrogentartarate have been elucidated in the solid-state by means of linearpolarized solid state IR-spectroscopy (IR-LD) of oriented solids as a colloid suspension in nematic hosts. Some limitations of the method are discussed as well.

Tert-butyl esters of 2,3-diaryl-3-arylaminopropanoic acids - stereoselective synthesis, isolation, spectroscopic and structural elucidation

“…Nonpolarized solid-state IR spectra were recorded using the KBr pellets technique. The oriented samples were obtained as a suspension in a nematic liquid crystal (MLC 6815, Merck) with the presence of an isolated nitrile stretching IR-band at about 2245 cm -1 additionally serving as an orientation indicator [9][10][11][12][13][14][15][16][17] . Ultraviolet (UV-) spectra were recorded on Tecan Safire Absorbance/Fluorescence XFluor 4 V 4.40 spectrophotometer operating between 190 and 900 nm, using solvent ethanol (Uvasol, Merck product) at a concentration of 2.5.10 -5 M in 0.921 cm quarz cells.…”

“…TD DFT and CIS calculations are performed for elucidation of the theoretical optical properties of the seven compounds in solution. The theoretical approach is described in [9][10][11][12][13][14][15][16][17] .…”