Study of inclusion complex of β-cyclodextrin and diphenylamine: Photophysical and electrochemical behaviors

The photophysical, electrochemical and photoprototropic behaviors of diphenylamine (DPA) in aqueous β-cyclodextrin (β-CD) solution have been investigated using absorption spectroscopy and cyclic voltammetric techniques. Absorption of the neutral and cationic form of DPA is enhanced due to the formation of a 1:1 complex with β-CD. The formation of this complex has been confirmed by Benesi–Hildebrand plot and docking studies by RasMol tool methods. The solid complex of β-CD with DPA is investigated by FT-IR, XRD and AFM methods. The thermodynamic parameters (ΔG, ΔH and ΔS) of inclusion process are also determined. The pKa values of neutral-monocation equilibria have been determined with absorption (conjugate acid–base) titrations. A mechanism is proposed to explain the inclusion process.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Hydrophobic interaction plays a major role in the inclusion complex process. ► The binding constants and thermodynamic parameters were calculated. ► Solid complex characterized by FT-IR, XRD and AFM techniques. ► Electron transfer reaction mechanism proposed by electrochemical (CV) studies.