Spectral and proton transfer behavior of 1,4-dihydroxylanthraquinone in aqueous and confined media; molecular modelling strategy

Abstract

The formation of supramolecular complex between the various ionic solutions of 1,4-dihydroxyanthraquinone (1,4-DHAQ) and hydrophobic cavity of β-cyclodextrin (β-CD) was studied by UV–visible, fluorescence spectroscopy and cyclic voltammetry methods. The stoichiometric ratio of the inclusion complex was found to be 1:1 and the binding constant of the inclusion complex at 303K were calculated using Benesi–Hildebrand plot and the inclusion interaction was examined and the thermodynamic parameter (ΔG) of inclusion process is also determined. The oxidation and reduction reactions specific to 1,4-DHAQ is quasi-reversible occur in a complex mechanism. The stable inclusion of 1,4-DHAQ in β-CD is proved by the significant changes of redox activity characteristic for 1,4-DHAQ and good electrochemical stability of the complex. On the other hand, the solid complex prepared between β-CD and 1,4-DHAQ were characterized by FT-IR, XRD, DSC, SEM and 1H NMR methods. The β-CD and 1,4-DHAQ inclusion complex obtained by molecular docking studies in good correlation with the results obtained through experimental methods using PatchDock and FireDock servers. The virtual study of the energetically favourable complex is obtained by PM3 calculations and molecular orbital energy suggests that orientation B is more favored than the orientation A.