Interaction of α-diimine-chromium(III) complexes with non-ionic surfactant Triton X-100

Using either luminescence intensity or lifetime measurements, we have studied the binding interactions of Cr(NN)(3)(3+) (NN=α-diimine ligands) with non-ionic solutions of surfactant p-(1,1,3,3-tetramethylbutyl)phenoxypoly(ethylene glycol), Triton X-100 (TX-100). The titration curves consisted of two curved regions with different slopes. This biphasic behavior of lifetime-TX-100 concentration data revealed the presence of premicellar aggregates at low TX-100 concentration and the formation of normal micelles at high surfactant concentration. The results were analyzed with a model that includes binding of Cr(NN)(3)(3+) (probe) to small premicellar aggregates and to micelles. There is a good correlation between the hydrophobicity of the ligands of Cr(III) complex and the strength of the binding of the complexes to the micelles. A comparison with the binding of Cr(NN)(3)(3+) to sodium dodecylsulfate (SDS) is discussed.