Electrochemical and fluorescence spectroscopic studies on the formation of <span style="font-size:12.0pt;font-family:"Times New Roman","serif";mso-fareast-font-family: Calibri;mso-fareast-theme-font:minor-latin;mso-ansi-language:EN-IN;mso-fareast-language: EN-US;mso-bidi-language:AR-SA">inclusion complex of <i style="mso-bidi-font-style: normal">p</i>-aminophenol with β-cyclodextrin</span>

Abstract

<span style="font-size:12.0pt;font-family:" times="" new="" roman","serif";="" mso-fareast-font-family:calibri;mso-fareast-theme-font:minor-latin;mso-ansi-language:="" en-in;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The redox of <i style="mso-bidi-font-style:normal">p</i>-aminophenol in the presence of β-cyclodextrin has been investigated by Osteryoung square wave voltammetry in phosphate buffer (<i style="mso-bidi-font-style:normal">p</i>H 6.60). Electrochemical results indicate that β-cyclodextrin forms a 1:1 inclusion complex with quinoneimine, the oxidized product of <i style="mso-bidi-font-style:normal">p</i>-aminophenol, rather than <i style="mso-bidi-font-style:normal">p</i>-aminophenol itself. It causes both a decrease in the reduction peak current, (<i style="mso-bidi-font-style: normal">I_pc</i>), as well as a negative shift in the reduction peak potential, (<i style="mso-bidi-font-style:normal">E_pc</i>), for quinoneimine reduction. The relationship between <i style="mso-bidi-font-style: normal">I_pc</i> and the concentration of β-cyclodextrin has been studied. The dissociation constant of the inclusion complex as obtained by electrochemical method was found to be, <i style="mso-bidi-font-style:normal">K_d</i> = 9.9×10^-3 mol L^-1. The diffusion properties of free quinoneimine as well as in the presence of β -cyclodextrin have been investigated by double potential-step chronocoulometry. Fluorescence spectra gave evidence for the complexation and the dissociation constant determined spectroscopically, <i style="mso-bidi-font-style:normal">K_d</i> ’= 9.5×10^-3 mol L^-1, is in good agreement with that obtained by electrochemical methods.</span>