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EPR spectra of 2,2,6,6-tetramethylpiperidine-1 -oxyl (tempo) and of 4-amino-2,2,6,6-tetramethylpiperidine-1 -oxyl (tempamine) were obtained in ionic liquids composed of 1 -ethyl-3-methylimidazolium chloride, ImCl, and aluminum chloride and in mineral oil. In basic solutions, those containing a molar excess of ImCl, the rotational correlation time of tempamine was ca. 27 times longer than for tempo. This is probably the result of a specific interaction of melt species with the basic NH2 moiety of tempamine. The 14N hyperfine isotropic coupling constants of tempo, 16.0 G, and tempamine, 15.8 G, in basic solution are comparable to those in DMSO and DMF. In acidic solution the 14N hyperfine coupling constant of tempo, 20.5 G, is appreciably larger due to adduct formation with A1C13.

potassium perchlorate in acetonitrile does not allow the whole ligand to complex, so that ZFmax cannot be estimated. Method 2: [1 -(ZF°/ZF)]/[M] = Ks(b/a)(IF°/IF) -Ks. This method29 can be used to avoid the determination of ZFmax. From plots of [1 -(Zf°/Zf)]/[M] versus ZF°/ZF, Ks can be determinedfrom the intercept. The limitation of the method is that it emphasizes the error on the points close to ZF°. For instance, it is not suitable to calculate Ks in the case of the potassium salt where the variations in the fluorescence intensity are very weak.

the experimental one. To obtain better agreement between these curves, we calculated a truncated distribution function with a restriction upon the position of spin on the sphere by some sphere layer. The function for which the best agreement was obtained and the kinetics calculated with this function are shown in Figure 9 and 7. Using this function we also calcuated the spin echo Registry No. Carbomonoxy hemoglobin A, 9072-24-6; cysteine, 52-90-4; 3-(2-iodoacetamido)proxil, 27048-01-7.