Absorption Spectra of Coordination Compounds. V. The Hyperchromic Series of Ligands

The relation between the kind of ligands and extinction coefficients of the first absorption bands of cobaltic complexes has been discussed. The order of ligands as to the magnitude of the effect which they exert on extinction coefficients of the first bands has been determined empirically, thus NCS^-CrO_4^=SO_3^=NO_2^-CO_3^=C_2O_4^=en OH^-NO_3^-SO_4^=Br^-NH_3Cl^-H_2O. For pentammine cobaltic complexes with the sixth ligands, each of which is coordinated with an oxygen atom, a linear relation has been found to hold between νmax’s and εmax’s of the first bands. For complexes of the type [CoA4X2], the trans-isomer has larger εmax if X has more hyperchromic and trans-pairing effects than A. This investigation was supported by a grant from the Ministry of Education.