ISSN:
0894-3230
Keywords:
cryptand
;
fluorescence titration
;
lanthanide coordination
;
proton transfer
;
Chemistry
;
Theoretical, Physical and Computational Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Lanthanide [lanthanum(III), 2; europium(III), 3; and gadolinium(III), 4] cryptates of a tris-phenylphenol N8O3 Schiff-base cryptand (H3L) were synthesized by transmetallation with [Na(H3L)]ClO4·3H2O (1) and characterized by spectroscopic and crystal structure analyses. Both 3 and 4 are isomophous and isostructural. The complexes crystallize in the triclinic space group P-1 with cell parameters for 3 of a = 14.9833(2), b = 15.42670(10), c = 16.3770(3) Å, α = 75.3760(10), β = 68.2640(10), γ = 77.0540(10)° and Z = 2 and for 4 of a = 14.9976(3), b = 15.4417(3), c = 16.35350(10) Å, α = 75.4980(10), β = 68.3180(10), γ = 76.8790(10)° and Z = 2. The structures reveal that one lanthanide ion is unsymmetrically encapsulated in the cryptand cavity with a second ligand (solvent DMF). Solution NMR and solid structural studies demonstrated that there are intracavity and intermolecular proton transfer processes during lanthanide complexation towards the cryptand. A fluorimetric titration in acetonitrile for Eu(III) ion to 1 afforded a novel fluorescence intensity (IF)-equivalents of Eu(III) ion (x) plot signaling a quenching (0 〈 x 〈 0.2)-enhancement (0.2 〈 x 〈 1) change with formation of the kinetically stable 1:1 cryptate. An energy-transfer mechanism is discussed. Copyright © 1998 John Wiley & Sons, Ltd.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
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