Pathways of radiative and radiationless transitions in europium(III) solutions. Role of solvents and anions

Abstract

Absorption and emission spectra of europium perchlorate and europium nitrate have been measured in protonated and deuterated solvents (water, dimethyl sulfoxide, methanol, and acetonitrile). The line shape of these spectra is shown to depend strongly on the solvent and anion. Ion pairing takes place, depending on the combination of solvent and anion. Quantum yields and lifetimes of fluorescence from the ;Do level are reported. An isotopic enhancement factor of 40 is found in water, while in other solvents it is much smaller.The rate constants for radiative and radiationless processes are calculated, The radiationless constants range from about lo4 sec-' for light water to about 10 for deuterated dimethyl sulfoxide in which the fluorescent quantum yield on direct excitation to 5 D~ approaches unity. The suitability of this system for use as a liquid laser is indicated. It is shown that the anions also quench fluorescence. Radiationless rate constants for CNS-and NOa-anions are calculated to be about loa sec-l. Fluorescence from the 5D1 level is weak in all solvents. Its quantum yield is about to 10-6. The isotopic effect for this fluorescence is only 3. The probability for decay from the 6D1 level directly to ground state is about the same for all systems, ~0 . 5 , suggesting a common mechanism for this process.

The effect of deuteriation on the emission lifetime of inorganic compounds

“…This approach has been used extensively [29,[76][77][78][79] and is accurate to + 0. Recently Faulkner and coworkers [29,71] Deuteriation has also been employed to study the mechanism for energy transfer to solvent [4,24,80]. per C-H oscillator) [76,82].…”

New Trends in the Design of Luminescent Metal Complexes*

“…Some lanthanide ions, particularly Eu3+ and Tb3+, possess strong luminescent and long-lived excited states. For example, the lowest excited state of Eu; : , 5Do, lives 3.2 ms and emits with an efficiency of 0.8 in D20 solution at room temperature (Haas and Stein, 1971). Unfortunately, these ions are very poor light absorbers.…”

Luminescent lanthanide sensors for pH, pO2 and selected anions

“…The main quenching process in this third step ( Fig. 1) involves vibrational energy transfer to higher harmonics of solvent and ligand oscillators [10][11][12][13][14][15]. Quenching by OH and amine NH oscillators is particularly efficient with Eu, so that the ligand that binds the lanthanide ion should shield it effectively from proximate OH oscillators (i.e.…”