Ultraviolet measurements in potassium bromide disks of the 2:1 complexes of 8-aminoquinoline with the chlorides of Mg, Ni(II) and Pd(II), and the 1.1 complexes with the chlorides of Zn, Cd and Cu(II) show a shift toward shorter wavelengths from that of the 8-aminoquinoline in the 300 millimicron region. The extent of the shift is almost identical for the Mg, Zn, Cd, Ni(II) and Cu(II) chelates, indicating that the metals are equally effective in blocking the resonance between the amino group and the quinoline ring by the nitrogen-to-metal bond formation. The ultraviolet spectra of the complexes of 8-aminoquinoline in dioxane do reveal differences in the values of the long wavelength maxima. Absorption patterns in the 3 micron region reveal the expected decrease in the frequencies of the N-H stretching vibration on chelation.
Mary P. Coakley, "Absorption Spectral Studies of Complexes of 8-Aminoquinoline with Metal Halides," Appl. Spectrosc. 18, 149-152 (1964)