Dynamic and complexation study of hydroxy amide derivatives with some amine salts by 400 MHz 1H-NMR

In this study, T_1 and T_2 relaxation times of some β-hydroxy amide derivatives was measured at room temperature (25 0C) by 400 MHz 1H-NMR spectrometer. The motion of molecules was invastigated by finding τ_c correlation time from the rate of ( R_1)⁄(R_2= )((1⁄T_1 ))⁄(2(1⁄T_2 )). Besides, using 1H-NMR method, binding constant (K_a) and Gibbs free energy changes (∆G0) was determined by the complexation studies of β-hydroxy amide derivatives with some amine salts. T_1 times of Ar-OH, Amide-NH and Alcohol-OH groups in β-hydroxy amide 1 appears greater than the T_1 times of Ar-OH, Amide -NH and Alcohol groups in β-hydroxy amide 2 and 3. This result shows that - interactions as well as non-covalent intramolecular interactions in ligand 2 and 3 which carry more bulky groups. In the complexation studies, it was seen that although β-chiral hydroxy amide derivatives have non-covalent interactions (-, hydrogen bond, cation-, etc.) with D-, L-Tryptophan and D-, L-Phenylalanine Methyl ester salts, these interactions among the relevant ammonium salts are not strong enough to create a good enantioselectivity. τ_c values of all molecules are found in ns range. This indicates that τ_c correlation time which modulates the motion is based on dipolar interactions. Keywords: β-hydroxy amide, T_1, T_2, molecular dynamic, complexation, binding constant and correlation time.