Vibrational spectral studies of L-methionine L-methioninium perchlorate monohydrate

The infrared and laser Raman spectra of L-methionine L-methioninium perchlorate monohydrate were recorded at room temperature and the vibrational assignments of the observed wave numbers were made. The presence of both the carbonyl and the ionized carboxylic groups has been identified in the title complex. The L-methionine and L-methioninium the cation have different conformations. This together with the different environment has seen by the two -CH(2)- groups in each skeleton cause several of the group wave numbers to occur as doublets or as broad bands. The perchlorate anion was found to be in the T(d) symmetry in the methionine environment. The coordination to other ligands in the crystal through hydrogen bonding does not affect this symmetry. The extensive intermolecular hydrogen bonding in the crystal was identified by the shifting of bands due to the stretching and bending modes of the various functional groups. Fermi resonance has also been observed.     

Infrared and Raman spectroscopic studies of l-valine l-valinium perchlorate monohydrate

FT-IR and FT-Raman spectra were recorded and analyzed for l-valine l-valinium perchlorate monohydrate crystals. The wave number assignments have been made for the functional groups, viz. COOH, COO(-), --[NH(3)](+), C--(CH(3))(2), C--C--N and C--H. One of the two amino acid residues remains in the zwitterionic form while the other residue exists in the cationic form. The symmetry of the ClO(4)(-) anion has been found to be lowered corresponding to ClO(2) group. The hydrogen bonds that prevail between amino acid residues, perchlorate anion and water molecule influence the wave numbers of several stretching and deformation modes to deviate from the expected values.