Aqueous Ln(III) Luminescence Agents Derived from a Tasty Precursor

Abstract

The synthesis, aqueous stability and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7 (1)]. A very poor metal centered quantum yield with Eu(III) was observed (Φtot = 0.04 %), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) 5D0 emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the Near Infra-Red (NIR).

Aryl Bridged 1-Hydroxypyridin-2-one: Effect of the Bridge on the Eu(III) Sensitization Process

“…In either case, luminescence lifetimes were found to be a few order of magnitude lower in solution than at 77K, 36-38 …”

Lanthanide luminescence for functional materials and bio-sciences

“…Noteworthy features are the visible excitation of [Ln(20a) 3 (phen)] via an ILCT state 82 and the Scheme 2 Phosphinic acid-and hydroxypyridine-containing ligands. [68][69][70][71][72][73][74] Scheme 3 Carboxylic and polyaminocarboxylic acids. 75,[77][78][79][80][81]91,97 This , 0.17%.…”

Luminescence Resonance Energy Transfer in Heterodinuclear LnIII Complexes for Sensing Biologically Relevant Anions

“…However, lanthanides such as Yb III and Nd III are being explored for their use as probes because they emit in the near IR (NIR), which is beneficial for biological studies since NIR wavelengths are efficiently absorbed by cells. [28][29][30][31][32][33] Time-resolved luminescence lifetimes, luminescence intensity, [32] ratiometrics of emission bands, [11,13] excitation spectra, and polarization [34,35] of Ln III photoluminescence are characteristics that have been used to discriminate between anions of biological interest upon interaction with Ln III complexes. Dinuclear Ln III ion complexes are of interest as luminescent sensors partly because their anion binding properties are different than those of their mononuclear analogs.…”