MODIFICATIONS OF THE ABSORPTION SPECTRA OF ANIONS INDUCED BY COMPLEX FORMATION
Creators:Katzin, L. I.
MetadataShow full item record
Publisher:Ohio State University
Since the majority of inorganic anions are colorless and the ions of metallic elements which most readily form chemical complexes with anions are generally colored, the altered absorption spectrum produced in the visible region of the spectrum by the complex formation is usually referred to as the absorption spectrum of the complex. However, the absorption spectrum of the nitrate ion, with a characteristic peak at about 300 millimicrons, is altered by complexing with metal ions; and in a given case one can identify shifts of both the anion and cation absorption spectra. The type of nitrate absorption shift found is related to the electronic configuration of the metal atom. Thiocyanate ion also has an absorption in part in reach of the Beckman spectrophotometer ($> 220$ millimicrons), and in tertiary butyl alcohol medium can be shown to give a markedly shifted absorption in the presence of cobaltous or nickelous perchlorate, while the spectra in the visible region show the characteristic changes in the absorption of the metal ion. Solid lithium chloride (and hence, presumably, chloride ion) absorbs far in the vacuum ultraviolet. Solutions of lithium chloride in tertiary butyl achohol do not absorb appreciably above background in the region above 220 millimicrons, and neither does cobaltous perchlorate. In mixture, strong absorption in the region 220-260 millimicrons is apparent, in addition to the characteristic cobalt chloride blue color in the visible region. Nickelous perchlorate, in similar fashion, evokes a characteristic absorption spectrum in the same region of the ultraviolet. Bromide and iodide ions, which absorb in the ultraviolet above 220 millimicrons, also show spectral modifications on forming complexes and allow one to follow the changes in greater detail. Some features of the quantitative relations of the absorptions are to be pointed out.
Author Institution: Chemistry Division, Argonne National Laboratory
Items in Knowledge Bank are protected by copyright, with all rights reserved, unless otherwise indicated.