Jb. Lamture et al., LUMINESCENCE PROPERTIES OF TERBIUM(III) COMPLEXES WITH 4-SUBSTITUTED DIPICOLINIC ACID ANALOGS, Inorganic chemistry, 34(4), 1995, pp. 864-869
The spectral properties of Tb(III) complexes with a series of 4-substi
tuted analogues of dipicolinic acid (2,6 pyridinedicarboxylic acid) we
re compared. Analogues in which the 4-substituent was -H, -OH, -Cl, -B
r, -NH2, or -NHAc all sensitized emission from bound terbium ions when
excited with ultraviolet light. Molar extinction coefficients of the
complexes at the wavelengths of maximum absorbance were in the range (
2.2 x 10(3) to 8.3 x 10(3)) M(-1) cm(-1) with magnitudes in the follow
ing order: NHAc > NH2 > OH > H > Br > Cl. When excitation spectra of T
b(III) complexes were measured under identical conditions for each lig
and, the maximum Tb(mj emission intensities were in the following orde
r: NH2 > NHAc > OH > K > Cl similar to Br. Measurements of Tb(III) emi
ssion decay kinetics revealed lifetimes in the range 1.0-2.0 ms. Relat
ive quantum yields for energy transfer were ordered as follows: NH2 >
OH > NHAc > Cl > H similar to Br. Energy transfer efficiency was not e
nhanced when Br was substituted for Cl at the 4-position, consistent w
ith energy transfer from excited singlet, rather than triplet states.
The efficient sensitization of Tb(III) emission by the analogues with
nitrogen at the 4-position suggests that this class of compounds will
be most useful for developing millisecond luminescence probes for bioa
nalytical studies.