Medium effects on the photophysical properties of terbium(III) complexes with pyridine-2,6-dicarboxylate.
Emission quantum yields and excited-state lifetimes of mono-, bis- and tris-complexes of terbium(III) with pyridine-2,6-dicarboxylate (DPA) have been measured for aqueous solutions as a function of pH and in the presence of six different anions: bromide, chloride, sulfate, perchlorate, acetate and nitrate. The state of ligation of the terbium ion had a more dramatic effect on photophysical properties of the complexes in comparison with the alteration of other medium parameters. An increase in the number of DPA ligands, coordinated with Tb3+ (from zero to three) resulted in an increase in the emission quantum yield from 0.06 to approximately 0.4, with concurrent prolongation of the excited-state lifetime from 0.5 to approximately 2 ms. It was determined that both an increase in the non-radiative decay rates and a decrease in the values of the radiative decay rate constants, contribute to the luminescence quenching that was detected when the number of DPA ligands was decreased and/or the media acidified. The purpose of this investigation is to aid in the establishment of optimal conditions for conducting terbium(III)-based emission assays for DPA, which is found in the coats of endospores.
Jones
Guilford
G
Department of Chemistry, Photonics Center, Boston University, Boston, MA 02215, USA. jones@chem.bu.edu
Vullev
Valentine I
VI
D000838:Anions / Q000737:chemistry; D002264:Carboxylic Acids / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D008163:Luminescent Measurements; D009942:Organometallic Compounds / Q000737:chemistry*; D010777:Photochemistry; D011725:Pyridines / Q000737:chemistry*; D011789:Quantum Theory; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013725:Terbium / Q000737:chemistry*
D000838:Anions; D002264:Carboxylic Acids; D008024:Ligands; D009942:Organometallic Compounds; D011725:Pyridines; D013725:Terbium