Lanthanide Complexes of a Calix[4]arene Ligand with Dangling Phosphonate and Picolinamide Arms: Synthesis, Crystal Structures, and Extraction Properties

Abstract

The coordination behavior of the neutral calix[4]arene-based ligand L exhibiting dangling phosphonate ester and picolinamide groups in 1,3-and 2,4-distal positions towards a series of lanthanide ions was examined. Reaction of L with Ln(NO 3 ) 3 in MeOH afforded mononuclear [LnL(μ 1,3 -NO 3 ) 2 ]NO 3 complexes [Ln = La (6), Pr (7), Eu (8), Gd (9)]. X-ray crystallography for 6 and 7 revealed tenfold coordination by phosphoryl O, amide O, and pyridine N atoms from L and four O atoms from two chelating nitrato coligands. Treatment of the [LnL(μ 1,3 -NO 3 ) 2 ]NO 3 salts with NaBPh 4 leads to metathesis of the counterion and, in the case of Pr, Eu, and Gd, to substitution of one nitrato coligand by a methanol molecule yielding [LnL(μ 1,3 -NO 3 ) 2-n (MeOH) n ](BPh 4 ) n+1 for n = 0, Ln = La (10) and [a] 3113 Scheme 3. Synthesis of lanthanide complexes 10-13 by nitrate metathesis.

Tetra‐Substituted p‐Tert‐Butylcalix[4]Arene with Phosphoryl and Salicylamide Functional Groups: Synthesis, Complexation and Selective Extraction of f‐Element Cations

“… [23] The synthesis of the substituent educts and precursor calix[4]arenes are described by Glasneck et al. [23] and with additional synthesis and analytical details in the Supporting Information in this paper.…”

“…The effects of the ligand modification on the extraction properties are discussed and compared with those of the previously reported neutral ligand L′ (Scheme 1 ). [23] …”

Dinuclear lanthanide complexes supported by a hybrid salicylaldiminato/calix[4]arene-ligand: synthesis, structure, and magnetic and luminescence properties of (HNEt3)[Ln2(HL)(L)] (Ln = SmIII, EuIII, GdIII, TbIII)

“…48 Only a handful of structures with triply appended calix [4]arenes have been reported, 49 and as far as we are concerned no structures exist with one-armed calix [4] arenes. 50 To fill this gap, we decided to prepare a mono-substituted calix [4]arene-Schiff base ligand H 4 L and investigate its coordination chemistry towards some lanthanide ions. Hybrid ligands of this sort are known to complex first-row transition metals readily, but their lanthanide chemistry remains largely unexplored.…”

Scaling up the Synthesis of a Hydroxyquinoline-Functionalized p-tert-Butylcalix[4]arene

“…To this end, modifications to a p-tert-butylcalix [4]arene scaffold were undertaken with the objective of (i) separating felements from other elements in aqueous solutions arising from ore leachates and (ii) separating f-elements from one another, particularly actinides from lanthanides, thereby achieving radioactive decontamination. The most suitable molecules arising from our research that fulfill both these objectives are respectively: (i) a tetraphosphonate-functionalized p-tert-butylcalix [4]arene based on the work by Glasneck et al 36 and (ii) the hydroxyquinoline-functionalized p-tertbutylcalix[4]arene 4 described by Jaschke et al 37 The solvent extraction performance of both these molecules is described by Schreiter et al 38 Bidentate ligands containing hard O-donors are very suitable for efficient extraction of trivalent actinides and lanthanides from solutions. 39 In combination with a soft N-donor, the ligand exhibits selectivity for actinides over the lanthanides due to differences in the way 5f-and 4f-cations are complexed.…”