- Techniques have been developed which utilize laser-induced luminescence of europium(III) ions to probe the environment of the metal ion.
Structural information is obtained from ligand field splittings measured on the excited ('5)D(,1) and ('5)D(,2) levels by excitation spectroscopy and on the various J-components of the ground ('7)F term by moderately high resolution emission spectroscopy. A comparison of spectra recorded on solution phase Eu(III) with those obtained on crystalline solids provides information regarding the similarities or differences in the environment of the metal ion in these systems.
A technique has been developed which utilizes excited state Eu(III) ions as probes to study dynamic processes occurring in an equilibrium system. The method involves monitoring the time course of the luminescence following selective excitation of the ('7)F(,0)(--->)('5)D(,0) electronic transition of a particular Eu(III) species with a pulsed dye laser. For two Eu(III) complexes together in solution and related by a ligand exchange reaction three classes of behavior for the time course of luminescence have been observed. An example of each class is given.
For systems where the rate of ligand exchange is either much slower (slow exchange) or much faster (rapid exchange) than the individual reciprocal excited state lifetimes qualitative information about the rate of exchange is obtained. A method for determining the individual excited state lifetimes of two rapidly interconverting species is demonstrated.
For systems where the rate of ligand exchange is comparable to the rate of luminescence decay quantitative information is obtained. The experiment depends upon selective excitation of a particular Eu(III) species while monitoring the time course of luminescence, either from predominately the same species or one into which it is converted at a rate comparable to the reciprocal excited state lifetime of the species involved. Forward and reverse rate constants for the equilibrium between the europium(III) complex of 1,2-diaminocyclohexanetetraacetate, Eu(DCTA)('-), and iminodiacetate, IMDA('2-), to form the ternary complex Eu(DCTA)(IMDA)('3-) are obtained using this method. The results are: k(,f) = 1.6 x 10('7) m('-1)sec('-1), k(,r) = 2.6 x 10('3) sec('-1), K(,eq) = 6.3 x 10('3) m('-1).
- Dissertation Note:
- Ph.D. The Pennsylvania State University 1982.
- Source: Dissertation Abstracts International, Volume: 43-10, Section: B, page: 3231.
View MARC record | catkey: 13611766