Inclusion complex of Alizarin Red S with β-cyclodextrin: Synthesis, spectral, electrochemical and computational studies

Inclusion complex formation of Alizarin Red S (ARS) with β-cyclodextrin was studied by UV-visible, Fourier transform infrared (FTIR), nuclear magnetic resonance (NMR), cyclic voltammetry (CV) and molecular modeling methods. FTIR and NMR results had justified that ARS was partly included into the β-CD cavity. The inclusion complex has 1:1 stoichiometry, where the apparent formation constant achieved was 4.137 × 103 L/mol using Benesi-Hildebrand equation. Cyclic voltammetry results shows the peak current decreased as the ARS molecule entered the hydrophobic cavity of β-CD. Molecular modeling results showed that the aromatic ring of the ARS entered into the secondary hydroxyl rim of the CD cavity was more thermodynamically favorable. The lowest stabilization energy, ΔE was −17.80 kcal/mol, and dipole-dipole interaction is was one of the driving forces for the inclusion complex formation.