determined from linear plots as before; for [Zn(HS),L]+ log 01 = 11.6, for [ZnL2]log p2 = 23.2. Variation of optical properties with the extent of chelation is the same here as has been previously found with other metallic ions and ligands of the 8quinolinol family (4,6). The zinc-2methyl-8-quinolinol system, however, does illustrate the importance of the environment of the metallic ion on the optical properties of the chelates. By comparing the two forms of the 1:l species the effect of the solvation shell composition is revealed. The relatively minor effect of removing a proton from the coordinated solvent molecule on the position and intensity of the long wavelength absorption band is not surprising, This band arises from the excitation of n-electrons of the ligand and its position has been shown to
vary only by small amounts when the metallic ion is changed, whereas its intensity seems to depend almost entirely on the ligand-to-metal ratio of the chelate ( 7 ) . The fluorescence characteristics of these chelates are, however, very sensitive to changes of the metallic ion and solvent (7, 9). Thus any changes in the environment of the chelated metallic ion, especially those affecting the polarity of neighboring species, may be expected to have a n effect similar to a change in solvent resulting in very marked alterations of the emission characteristics, especially the intensity, of the chelates.
LITERATURE CITED
(1) Bjerrum, J., Jorgensen, C. K., Acta Chem. Scand. 7, 951 (1953). (2) Lund, H., Bjerrum, J., Ber. M B , 210 (1931). (3) Kolthoff, I. M., Sandell, E. B., “Textbook of Quantitative Inorganic Analysis,” 3rd ed., p. 321. Macmillan, New York, 1955. (4) Ohnesorge, W. E., ANAL.CHEM.35, 1137 (1963). (5) Ohnesorge, W. E., Burlingame, A. L., Ibid., 34, 1086 (1962). (6) Ohnesorge, W. E., Capotosto, A., Jr., J . Inorg. Xucl. Chem. 24, 829 (1962).
(7) Ohnesorge, W. E., Rogers, L. B., Spectrochim. Acta 1950, p. 27. (8) Rossotti, F. J. C., Rossotti, H., “The Determination of Stability Constants,” pp. 92-4, McGraw-Hill, Xew York, 1961
ACKNOWLEDGMENT
The authors are grateful to Douglas
M. Rosie for his advice and assistance with the gas chromatographic analysis.
(9)-S
