Spectral characteristics of ortho, meta and para dihydroxy benzenes in different solvents, pH and β-cyclodextrin

Spectral characteristics of ortho, meta and para dihydroxy benzenes (DHB's) have been studied in different solvents, pH and β-cyclodextrin. Solvent study shows that: (i) the interaction of OH group with the aromatic ring is less than that of amino group both in the ground and excited states, (ii) in absorption, the charge transfer interaction of OH group in para position is larger than ortho and meta positions. pH studies reveals that DHB's are more acidic than phenol. The higher pKa value of oDHB (monoanion–dianion) indicates that the formed monoanion is more stabilized by intramolecular hydrogen bonding. DHB's forms a 1:1 inclusion complex with β-CD. In β-CD medium, absorption spectra of DHB's mono and dianions shows unusual blue shifts, whereas in the excited state, the spectral characteristics of DHB's follow the same trend in both aqueous and β-CD medium.