Modifications of the Absorption Spectra of Anions Induced by Complex Formation

Abstract

The absorption of thiocyanate, chloride, bromide, and iodide ions are markedly altered on complexing with nickelous or cobaltous ions in isopropyl alcohol solution, new peaks appearing at longer wavelengths. In the case of iodide ion, the absorption spectra of the complexes with nickelous ion, cobaltous ion, and iodine (the ``tri‐iodide'' complex) are practically distinguishable only by their extinction coefficients. A characteristic feature of the modified iodide spectrum is the pair of peaks, found at shorter wavelengths in the spectra of the free iodide ion, and in other forms. The cobaltous complexes with bromide and chloride ions show analogous splittings, but the absorption of the trihalide ions show single peaks which agree in wavelength with the longer‐wavelength peak of the cobalt‐complexed ion. The nickelous complexes absorb at shorter wavelengths.