79,81Br−127I−NQR, and Crystal Structure of Glycyl-l-alanine Hydrobromide Monohydrate and Hydroiodide Monohydrate

Abstract

Abstract The crystal structures of glycyl-l-alanine hydrobromide monohydrate, 1, and glycyl-l-alanine hydroiodide monohydrate, 2, were determined and the temperature dependence of the 127I NQR frequencies was investigated in the temperature range 77 <̳T/K <̳ 370. The 127I NQR frequencies are strongly influenced by hydrogen bonds and this is proved by the frequency shift of the H ⇄ D exchange. By deuteration the nuclear quadrupole coupling constant e2 qQh−1(127I) of 2 is shifted downwards 2.72 MHz at room temperature. The title compounds are isotype, and at room temperature they crystallize monoclinic with the space group C2 2 − P21 with two molecules in the unit cell. The lattice constants for 1 are a = 1068.7 pm, b = 614.1 pm, c = 762.0 pm, and β= 108.55° and for 2 are a = 1093.3 pm, 6 = 637.1 pm, c = 770.9 pm, and β= 107.29°.