Inclusion complexation of 3,5-dihydroxybenzoic acid with β-cyclodextrin at different p Hs

Effect of β-cyclodextrin on the absorption and fluorescence spectra of 3,5-dihydroxy benzoic acid has been studied in buffer solutions of different pHs (1, 7, 10). The study reveals that in all the studied pHs, DHB forms 1:1 inclusion complex. The hydroxyl group is present in the interior part of the β-CD cavity and carboxyl group is present in the hydrophilic part of the β-CD cavity. Dual luminescence is observed in pH~1 and pH~7 solutions which shows that intramolecular charge transfer is present in these pHs. The broad spectral maximum at pH~10 indicates intramolecular proton transfer in DHB.