title: Low-frequency vibrational modes of DL-homocysteic acid and related compounds.
abstract: In this paper several polycrystalline molecules with sulfonate groups and some of their metal complexes, including DL-homocysteic acid (DLH) and its Sr- and Cu-complexes, pyridine-3-sulphonic acid and its Co- and Ni-complexes, sulfanilic acid and L-cysteic acid were investigated using THz time-domain methods at room temperature. The results of THz absorption spectra show that the molecules have characteristic bands in the region of 0.2-2.7 THz (6-90 cm(-1)). THz technique can be used to distinguish different molecules with sulfonate groups and to determine the bonding of metal ions and the changes of hydrogen bond networks. In the THz region DLH has three bands: 1.61, 1.93 and 2.02 THz; and 0.85, 1.23 and 1.73 THz for Sr-DLH complex, 1.94 THz for Cu-DLH complex, respectively. The absorption bands of pyridine-3-sulphonic acid are located at 0.81, 1.66 and 2.34 THz; the bands at 0.96, 1.70 and 2.38 THz for its Co-complex, 0.76, 1.26 and 1.87 THz for its Ni-complex. Sulphanilic acid has three bands: 0.97, 1.46 and 2.05 THz; and the absorption bands of l-cysteic acid are at 0.82, 1.62, 1.87 and 2.07 THz, respectively. The THz absorption spectra after complexation are different from the ligands, which indicate the bonding of metal ions and the changes of hydrogen bond networks. M-O and other vibrations appear in the FIR region for those metal-ligand complexes. The bands in the THz region were assigned to the rocking, torsion, rotation, wagging and other modes of different groups in the molecules. Preliminary assignments of the bands were carried out using Gaussian program calculation.
authors.affiliation: State Key Laboratory of Nuclear Physics and Technology, Institute of Heavy Ion Physics, School of Physics, Peking University, Beijing 100871, China. yanglm@pku.edu.cn
authors.forename: Limin
authors.initials: L
authors.lastname: Yang
authors.forename: Guozhong
authors.initials: G
authors.lastname: Zhao
authors.forename: Weihong
authors.initials: W
authors.lastname: Li
authors.forename: Yufeng
authors.initials: Y
authors.lastname: Liu
authors.forename: Xiaoxi
authors.initials: X
authors.lastname: Shi
authors.forename: Xinfeng
authors.initials: X
authors.lastname: Jia
authors.forename: Kui
authors.initials: K
authors.lastname: Zhao
authors.forename: Xiangyang
authors.initials: X
authors.lastname: Lu
authors.forename: Yizhuang
authors.initials: Y
authors.lastname: Xu
authors.forename: Datao
authors.initials: D
authors.lastname: Xie
authors.forename: Jinguang
authors.initials: J
authors.lastname: Wu
authors.forename: Jia'er
authors.initials: J
authors.lastname: Chen
mesh_terms: D003035:Cobalt / Q000737:chemistry; D003300:Copper / Q000737:chemistry; D003460:Crystallization; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000737:chemistry; D008024:Ligands; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D013055:Spectrophotometry, Infrared; D013324:Strontium / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry*; D055068:Terahertz Spectroscopy
chemical_list: D008024:Ligands; D008670:Metals; D011725:Pyridines; D013451:Sulfonic Acids; D006710:Homocysteine; C007956:homocysteic acid; D003035:Cobalt; D003300:Copper; D009532:Nickel; D013324:Strontium