Abstract: The inclusion of 2′-ethylhexyl-4-(N, N-dimethylamino)-benzoate (EHDAB) into methylated β-cyclodextrin (M-CD) and 2′-hydroxypropyl-β-cyclodextrin (HP-CD) was examined using molecular spectra. Both the flexible 2′-ethylhexyl chain and the rigid aromatic moiety of EHDAB were encapsulated within the cavity of M-CD and HP-CD, respectively. EHDAB was stabilized within the 2:1 cage-type host-guest inclusion complexes. The hydrophobic 2′-ethylhexyl tail greatly contributes to the extraordinarily stable complexes. M-CD and HP-CD increased the water solubility of EHDAB. The enhanced absorbance of EHDAB was obtained, and the photo-induced twisted intramolecular charge transfer of EHDAB was greatly suppressed by the restricted shape and size of the cavity. The photodegradation of EHDAB was markedly reduced in aqueous solution. EHDAB was still stable in alkaline solutions of M-CD and HP-CD. Anti-oxidation and thermal stability were appreciably promoted at the same time.

Key words: UV absorber, Cyclodextrins, Host-guest inclusion complexes, Photostability, Twisted intramolecular charge transfer, Anti-oxidation