Fluorescent terbium chelates derived from diethylenetriaminepentaacetic acid and heterocyclic compounds
A series of aminoaromatic derivatives of diethylenetriaminepentaacetic acid (DTPA) has been prepared, in a search for terbium chelates suitable for use in fluorescence immunoassay. Most of the derivatives contained heterocyclic rings with at least one nitrogen atom. The fluorescence properties of the terbium chelate of each compound were examined. Although none of the products proved suitable for use in immunoassays, the terbium chelate formed from the product of the reaction between DTPA anhydride and cytosine (4-amino-2-hydroxypyrimidine) was particularly fluorescent and had a long fluorescence lifetime. It was unstable, however, in aqueous solution below pH 9. The fluorescence properties of some europium complexes were also examined.