Synthesis, crystal structure, IR and Raman properties of 1,2-diacetamidocyclohexane and its complexes with ZnBr2 and HBr3

X-ray crystallography, infrared absorption and Raman scattering were applied to study the influence of Zn(II) or H+ on the amidic bond. (R,R)-1,2-diacetamidocyclohexane (DAACH) was chosen as a conformationally strained chiral building block including two amide bonds; this model is hoped to be not too far from a peptide and gives easily crystalline complexes. Crystallographic structures of DAACH molecule (1), DAACH/ZnBr2 (2) and DAACH/HBr3 (3) complexes were studied. Complexation of Zn by DAACH is due to the hyperpolarization of the amidic bond. IR and Raman studies of 1-3 agree with the X-ray results. This could be a model in the study of metal/proteins interactions or acidic denaturation of polypeptides