THE ABSORPTION SPECTRA OF THE COMPLEXES OF AROMATIC HYDROCARBONS WITH METAL IONS

Author Institution: Department of Chemistry, University of CaliforniaIt has been found that mesitylene forms complexes with all the metal ions except the alkali metals, strontium, and barium. The work also indicates that radium and thallous ions will not form complexes. The reaction is not restricted to mesitylene, but is found to be general with the aromatic hydrocarbons. Presumably, this is a Lewis acid-base reaction in which two of the $\pi$ electrons of the aromatic hydrocarbon are involved. The absorption spectra of a number of these complexes have been determined in solution and on the surface of silica gel. The solution spectra were obtained by dissolving the laurate of the metal in the hydrocarbon. The spectra were determined only above 2800 {\AA}. Below this wavelength, the solutions become essentially opaque due to the absorption of the hydrocarbon. The spectra of the complexes of silver, magnesium, zinc, manganous, aluminum, erbium, neodymium, and thorium laurates with mesitylene were determined. All of the complexes had a strong band with a maximum between 2900 and 2950 {\AA}. The molar extinction coefficients of the magnesium and aluminum complexes were found to be 160, thorium 600, manganese 4000, and the remainder were near 1000. On the surface of the gel, all the complexes except those of thorium and cerium had a band with a maximum at 5600. The spectra of the complexes on the surface were determined to 3200 {\AA}. It was not possible to work at shorter wavelengths below 5600 {\AA} there are a number of weaker band These bands are dependent upon the metal ion which is complexed. The intensity of the band at 5600 {\AA} varied as the ion potential. Measurements of the fluorescence of the complexes indicates that the 5600 band on the surface of the gel is probably due to a breakdown of selection rules in the asymetric field of the solid