Lanthanide Chelates Based on Diethylenetriamine Fitted with O‐Benzoic Acid Pendant Arms

Abstract

A new polycarboxylate ligand H 5 L has been synthesized by the attachment of five benzoate subunits onto a diethylenetriamine framework. Seven pK a values have been determined by potentiometry, spectrophotometry and NMR spectroscopy as 1.9(2), 2.8(2), 3.87(5), 4.58(6), 4.87(6), 9.19(6) and 11.68(5), the first four corresponding to the carboxylic functions and the last three to amine sites. The interaction between H 5 L and Ln III ions in dilute aqueous solution has been examined by UV/Vis absorption and emission spectrometries, and has been found to result in monometallic complexes that are moderately stable in the pH range 3.7−7.5. Conditional stability constants at pH 5.3 are logK 11 = 5.3(2), 6.6(1), 6.5 (1)

Stable 8-Hydroxyquinolinate-Based Podates as Efficient Sensitizers of Lanthanide Near-Infrared Luminescence

“…The nature and stability of the species forming between the Eu III ion and Tsox has been first probed at variable pH and in equimolar solutions of ligand and metal ion by potentiometric (pH range 1.72−12.22) and spectrophotometric titrations (pH range 1.71−12.34). This ion was chosen as a typical example because it lies in the middle part of the Ln III series, and in view of the podand nature of the ligands investigated which behave as predisposed receptors, not much difference in the stability of the resulting podates is expected along the lanthanide series. , The potentiometric titration curve of a 1:1 solution of the Eu III ion and ligand Tsox (Figure S6, Supporting Information) shows a pH variation, indicating the release of protons upon Ln III coordination. Furthermore, the formation of hydroxo-complexes is also detected.…”

Visible and Near-Infrared Intense Luminescence from Water-Soluble Lanthanide [Tb(III), Eu(III), Sm(III), Dy(III), Pr(III), Ho(III), Yb(III), Nd(III), Er(III)] Complexes

“…Here we present results concerned with a newly prepared water-soluble two-component system, ligand 1 , Scheme [ 1 is 4-[(9-methyl-1,10-phenantrol-2-yl)methyl]-1,4,7-triazaheptane-1,1,7,7-tetraacetic acid]. 1 features a combination of a single phenanthroline chromophore and a diethylenetriamine tetracarboxylic unit (DTTA ) hosting site, expected to provide highly stable complexes. − The coordination positions of the Ln(III) center are protected against solvent access, as shown by the comparison of luminescence results obtained in water and deuterated water (vide infra). We provide evidence that, for the 1:1 species obtained with ligand 1 ( K A > 10 7 M -1 ; see below), the luminescence sensitization process in air-equilibrated water is quite effective, resulting in φ se = 0.24 and 0.15 for the visible emitters Eu· 1 and Tb· 1 , respectively; φ se = 2.5 × 10 -3 , 5 × 10 -4 , 3 × 10 -5 , and 2 × 10 -5 for the vis and NIR emitters Sm· 1 , Dy· 1 , Pr· 1 , and Ho· 1 , respectively, and φ se = 2 × 10 -4 , 4 × 10 -5 , and 4 × 10 -5 for the exclusively NIR emitters Yb· 1 , Nd· 1 , and (in deuterated water) Er· 1 , respectively.…”

Tetracarboxylate Ligands as New Chelates Supporting Copper(II) Paddlewheel-Like Structures

“…The yield of the second step is only around 40% due to an intramolecular annelation reaction occurring in parallel with the N-alkylation, decreasing significantly the yield (see Scheme S1, Supporting Information). Hydrolysis of these esters affords the desired tetracarboxylate ligands 5 and 6 in a hexaprotonated form . Ligands 3 and 5 (as a hydrochloride salt) were characterized by X-ray crystallography (see below).…”