Spectral and photophysical studies on the inclusion complexation between Triton X-100 and β-cyclodextrin: A competitive method using a substituted 3H-indole probe

We report herein the interaction of the nonionic surfactant Triton X-100 with β-cyclodextrin (β-CD) using 2-(p-aminophenyl)-3,3-dimethyl-5-carboethyoxy-3H-indole (1) as a fluorescent probe through a competitive method. The formation of 1:1 and 1:2 (guest:host) inclusion complexes was confirmed and the association constants were estimated. Using Triton X-100 itself as a probe, the interaction pattern and the association constants obtained were in agreement with those sensed by 1. Furthermore, the binding site of Triton X-100 with β-CD was investigated. It was found that the entire hydrophobic part of Triton X-100 was included into the cavity of β-CD. For comparison, we also employed 1 as a probe to study the interaction between Brij 56 and β-CD. The above results strongly suggest that molecule 1 is a good candidate acting as a probe to study the inclusion complex between a non-fluorescent guest and cyclodextrin.