Selective Binding of Group IIIA and Lanthanide Metals by Hexahomotrioxacalix[3]arene Macrocycles

Daitch, Charles E.; Hampton, Philip D.; Duesler, Eileen N.; Alam, Todd M.

doi:10.1021/ja9605984

Cited by 39 publications

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“…The La(L) complex is structurally similar to that previously reported for the La complex of /?-te^butylhexahomotrioxacalix [3]arene (14) (10) The La centers in complexes 4 and 14 are coordinated to the three phenolic oxygen atoms and the three ring heteroatoms (Ο, N). For complex 4, the complex possesses a tricapped trigonal prismatic structure where the remaining coordination sites are occupied by the ester carbonyl groups.…”

Section: Isolation Of Group 3 Metal-ion Complexes Of the Azacalix[3]asupporting

confidence: 82%

Molecular Recognition by Azacalix[3]arenes

Hampton

Chirakul

et al. 2000

ACS Symposium Series

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The azacalix[3]arene macrocycles 1 are ideal hosts for the binding of metal ions and alkylammonium ions due to the presence of heteroatoms in the macrocycle ring and the ease of modifying their structure through the R, R', and R" substituents. Synthetic routes to the azacalix[3]arene macrocycles will be discussed from the perspective of their ability to generate the azacalix[3]arenes 1 free from the corresponding azacalix[4]arenes 2.Azacalix[3]arene macrocycle 1a exhibits the ability to bind trivalent metal ions and form complexes where the macrocycle is either a neutral (H 3 L) or a trianionic (L 3-) donor. Crystal structures of well-defined yttrium(III) [3: Y(H 3 L)Cl 3 ] and lanthanum(III) [4: La(L)] complexes are reported. Molecular recognition studies have been performed on the azacalix[3]arenes 1.In contrast with the O-unsubstituted macrocycles (1, R"= H) which exhibit no detectable binding of alkali or ammonium ions, the O-methylated macrocycle 1j is observed to extract alkali metal and alkylammonium picrates.The hexahomotriazacalix[3]arene macrocycles 1 (Figure 1), abbreviated to azacalix[3]arenes in this paper, are interesting targets for molecular recognition and ion separation studies since their structure can be modified at not only the upper-rim (R) and lower-rim (R"), but also within the macrocycle cup at the inner-rim (R') (/-4). The azacalix[3]arenes have received only limited attention for their molecular recognition behavior; this is probably due to the difficulty of synthesizing the macrocycles free from the corresponding cyclic tetramers, the azacalix[4]arenes 2 (/).Takemura and co-workers first reported that the azacalix[3]arenes lb-e could be synthesized (Eq. 1) by heating 2,6-bis(hydroxymethylphenols) 5 in the presence of a primary amine in refluxing toluene (2-4). The azacalix[3]arenes were reported to be isolated without contamination by the corresponding azacalix[4]arenes 2. They also reported that azacalix[3]arene lb could be O-alkylated with picolyl chloride to yield macrocycle If but the cone vs. partial-cone selectivity of this reaction was not discussed (4). Macrocycle lb was reported to extract U0 2 2+ from aqueous solutions.

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Section: Isolation Of Group 3 Metal-ion Complexes Of the Azacalix[3]asupporting

confidence: 82%

Molecular Recognition by Azacalix[3]arenes

Hampton

Chirakul

et al. 2000

ACS Symposium Series

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“…The data obtained in [32] indicate that degree of cupping increased with growing metal ion whereas the µ-aryloxy bonds weakened.…”

Section: Receptor Properties Of Hexahomotrioxacalix[3]arenes With Frementioning

confidence: 94%

“…The study of NMR spectra of complexes 3335 in toluene-d 8 [32] revealed their fluxional behavior. The spectral data indicate that in 35 in toluene-d 8 occurred a rupture of a m-aryloxy bond followed by rotation around the remaining µ-aryloxy bond.…”

Section: Receptor Properties Of Hexahomotrioxacalix[3]arenes With Frementioning

confidence: 98%

“…The constants of complex formation amounted respectively for Na + cation to 0.39 l mol 1 , for ions K + and Li + to 0.32 and 0.11 l mol 1 . Oxacalixarenes 2 and 32 form stronger complexes with trivalent metals Sc 3+ , Lu 3+ , Y 3+ , and La 3+ than with alkali or alkaline-earth metals [32,33]. The constants of complex formation grow in the following sequence: Na + , Li + , Ca 2+ < Mg 2+ < La 3+ << Y 3+ < Lu 3+ << Sc 3+ , and the constants for ligand 2 are smaller than those of ligand 32 [33].…”

Section: Receptor Properties Of Hexahomotrioxacalix[3]arenes With Frementioning

confidence: 99%

“…A reaction of oxacalixarene 2 with Lu 3+ , Y 3+ , or La 3+ triflates in a mixture DMSOCH 3 CN in the presence of Et 3 N furnished complexes [M(L)(DMSO) 2 ] 2 (3335) [32] where M = Lu (33, 74%), Y (34, 83%), La (35, 48%); L is the trianion of macrocycle 2. All complexes in solid state or non-coordinating solvents (toluene) exist as dimers with a symmetry center whose core is constituted by µ-aryloxo bridges.…”

Section: Receptor Properties Of Hexahomotrioxacalix[3]arenes With Frementioning

confidence: 99%

See 2 more Smart Citations

Homooxacalixarenes: II. Receptor properties

Shokova

Ковалев

2004

Russ J Org Chem

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Finessen mit Schwefel: Calixarene als Uranophile

Asfari¹,

Bilyk

Dunlop

et al. 2001

Angew. Chem.

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Hinweise darauf, dass mit Donoratomen versehene Calixarene als selektive Liganden für U VI (in Form von UO 2 2 ) dienen könnten, [1] haben das Interesse an den Koordinationsmodi von Uran in solchen Spezies geweckt. [2] In frühen Arbeiten [3, 4] über die Synthese von UO 2 2 -spezifischen Liganden, so genannten ¹Uranophilenª, [5,6] nahm man angesichts der Tatsache, dass für UO 2 2 -Komplexe übliche Geometrien für andere Metallionen kaum bekannt sind, [7] an, dass Liganden mit im Wesentlichen planaren pentagonalen oder hexagonalen Donoratomanordnungen am geeignetsten sind. Dieses Konzept [1] diente auch als Erklärung für die selektive Bindung von UO 2 2 durch eine Reihe von (wasserlöslichen) Calix[6]arenen, wobei bei dieser Betrachtung allerdings mehr die Geometrie, denn die Abmessungen der Donoratomanordnung und die Art der Donoren im Mittelpunkt standen. Der Vorschlag, dass hier möglicherweise sechs Phenoxiddonoren beteiligt sind, scheint von der allgemein bekannten Koordinationschemie von UO 2 2 mit Alkoxidliganden abzuweichen, [8] denn bislang wurden nur nahezu oktaedrische Spezies mit vier solcher Liganden gefunden. U VI -Alkoxide [U(OR) 6 ] sind zwar bekannt, [8] aber sie sind nicht unter den Bedingungen stabil, unter denen Uranylionen/Calixaren-Komplexe durch Lösungsmittelextraktion hergestellt werden, wenngleich sich derartige Spezies mit einem Calix[6]arenliganden in seltenen Fällen bilden können. Bemerkenswerterweise ergab die Strukturaufklärung eines Pyridin-stabilisierten U VI -Derivates von p-tBu-Calix[6]aren, [9] dass für eine oktaedrische Koordination zwei Ligandmoleküle benötigt werden, die beide als dreizähnige Donoren in einer 1,2,3alternate-Konformation fungieren. In Kristallstrukturen von UO 2 2 -Komplexen mit Calixarenen, die ausschlieûlich Phenoxiddonoren enthalten, koordinieren maximal vier Phenoxidgruppen, die die äquatorialen [*] Prof.

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Selective Binding of Group IIIA and Lanthanide Metals by Hexahomotrioxacalix[3]arene Macrocycles

Cited by 39 publications

References 39 publications

Molecular Recognition by Azacalix[3]arenes

Molecular Recognition by Azacalix[3]arenes

Homooxacalixarenes: II. Receptor properties

Finessen mit Schwefel: Calixarene als Uranophile

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