Studies of the Absorption Spectra of Azo Dyes and their Metalcomplexes. III. The Electronic Absorption Spectra of Metalcomplexes Derived from Phenolazoacetoacetanilides

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Abstract 1) The electronic absorption spectra of metallized phenolazoacetoacetanilides exhibit four characteristic groups of bands—A, B, C and D. These groups of bands originate in the band of the respective ligand-dye. 2) The metal-complexes have the structure shown in formula VI. 3) The bathochromic shifts of the A ligand-bands with complex-formation are ascribed to two causes: (i) the polarity of the M–O (M, tervalent metal; O, phenolic oxygen) bond, and (ii) the perturbation of the π-electron system by the dπ-pπ interaction. The shifts of the C ligand bands with the complex-formation are closely related to the polarity of the above-mentioned M–O bond. The cobalt (III)-complex has the covalent M–O bond with which to form a stable chelate ring, whereas the chromium (III)-complex has the ionic M–O bond. 4) The absorption characteristics of the iron (III)- and the aluminum-complexes have been discussed.