Study on β-cyclodextrin inclusion of Zn(II) aromatic complex and its analytical application

A new β-cyclodextrin (β-CD) inclusion compound Zn(2H1NA)2·2β-CD (2H1NA = 2-hydroxy-1-naphthoic acid) was prepared. The structure was characterized by 1H NMR, IR, the fluorescence spectra, thermogravimetric analysis (TG–DTA) and elementary analysis. Meanwhile, the mechanism of the formation of the supramolecular system (2H1NA:Zn(II):β-CD) was studied and discussed by spectrofluorimetry. The results showed that the naphthalene rings of the Zn(II) aromatic complex Zn(2H1NA)2 were encapsulated within the β-CD's cavity to form a 2:1 stoichiometry host–guest compound. The inclusion constant calculated was 1.27 × 104 (L/mol)2. A spectrofluorimetric method for the determination of 2H1NA in bulk aqueous solution in the presence of β-CD was developed based on the great enhancement of the fluorescence intensity of 2H1NA. The linear relationship was obtained in the range of 9.00 × 10−7 to 2.50 × 10−5 mol/L and the detection limit was 8.00 × 10−7 mol/L. The proposed method was successfully applied to determine 2H1NA in waste water with recoveries of 97–104%.