Substituent-Group Effects on the Fluorescence of Aluminum–Schiff Base Complexes and Their Application to the Determination of Aluminum

Abstract

Abstract The effects of the substituents in the Schiff-base N-salicylidene-o-aminophenol (SOAP) on the fluorescence of its aluminum complexes were investigated. N,N′-Disalicylideneethylenediamine (DSED) derivatives were used as aldehyde reagents for the condensation to prepare 25 different SOAP compounds, for these reagents can be conveniently hydrolyzed to yield salicylaldehyde derivatives. o-Aminophenol (OAP) derivatives were used as amine reagents for the SOAP compounds. A methoxyl group at the 4-position of the benzylidene group in the Schiff base and a sulfo group at the 5-position in the amine component increased the fluorescence intensity of the complex. The relationship between the fluorescence intensity and the structure of the complex was investigated by the Free-Wilson method of estimation, and good agreements were obtained between the experimental and the calculated values of the fluorescence intensities. The fluorometric determination procedure of aluminum was established by using 4,4′-dimethyl DSED and 4-sulfo OAP. Aluminum can be accurately determined in the range from 0.001 to 3 μg/25 ml under optimum conditions.