Novel ligands, diethylenetriaminepentaacetic acid bearing several aromatic amines, were synthesized and their chelates with a europium ion were prepared. The lanthanide luminescence of the chelates of 1-aminonaphthalene and 7-amino-4-methylcoumarin was largely enhanced by the energy transfer from the ligand to the europium ion.
Bichromophoric naphthalene derivatives of diethylenetriaminepentaacetate (DTPA): fluorescent response to H<sup>+</sup>, Ca<sup>2+</sup>, Zn<sup>2+</sup>, and Cd<sup>2+</sup>
of the complexes. The insertion of CH2 spacer intensifies the emission and enhances the selective response to metal ions: the excimer emission is strengthened by 70−100 % with Cd2+ coordination, weakened by 60 % with Zn2+, and insensitive to Ca2+. The high response of methylnaphthyl bichromophores to Cd2+ is advantageous in fluorometric analyses. GRAPHICAL ABSTRACT