Inclusion Complex of Thiourea Substrate with Hydroxypropyl-β-cyclodextrin

To be active, a heavy metal trap substrate must possess some degree of aqueous solubility. The use of cyclodextrins molecules, which can form inclusion complexes with the hydrophobic trap substrates, has provided the required solubility through the relatively hydrophobic cavity of native cyclodextrins and their derivatives that enhances the ability to complex hydrophobic substrates of appropriate size and shape. In this study, spectrophotometry has been used to investigate the effects of cyclodextrin on the solubility, stoichiometry and stability of the substrate-CD complex formed between N-(2-ethylphenyl)-N'-(2-methylphenyl) thiourea, (a hydrophobic substrate trap) and hydroxypropyl-β-cyclodextrin (HP−β−CD). The solubility, stoichiometry and overall association constant of the complex have been determined using the Higuchi's method, the continuous variation (Job's plot) method and the Scott's method respectively.