Straightforward synthesis and catalytic applications of rigid N,O-type calixarene ligands

Rawat, Varun; Press, Konstantin; Goldberg, Israel; Vigalok, Arkadi

doi:10.1039/c5ob01987g

Cited by 15 publications

(16 citation statements)

References 57 publications

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“…[H 2 (bpzCal)], [8] [Cu(HMDS)] 4 [9] and [(PPh 3 )Au(MeCN)]SbF 6 [10] were prepared according to literature procedures.…”

Section: Methodsmentioning

confidence: 99%

“…[Cu(MeCN) 4 ]BF 4 was purchased from TCI, AgSbF 6 from Alfa Aesar and (PPh 3 )AuCl from ABCR; the reagents were used as received. [H 2 (bpzCal)], [Cu(HMDS)] 4 and [(PPh 3 )Au(MeCN)]SbF 6 were prepared according to literature procedures.…”

Section: Methodsmentioning

confidence: 99%

“…The molecular structure of 4; selected bond lengths /Å and angles /°: Au1-N1 2.056(3), Au1-P1 2.2381(8), N1-Au1-P1 173.40(8). Hydrogen atoms (apart from the OH protons) are omitted for clarity.…”

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confidence: 99%

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The Coordination Behavior of Oxygen‐depleted Calixarenes towards d¹⁰ Noble Metal Ions

Keck

Hoof

Rawat

et al. 2020

Zeitschrift anorg allge chemie

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A calix[4]arene, in which two of the phenol functions are replaced by pyrazole units, [H2(bpzCal)], was investigated as a ligand for Cu+, Ag+ and Au+ ions. Using [Cu(MeCN)4]BF4 and AgSbF6 as the precursors, complexes [MH2(bpzCal)]X (M = Cu, X = BF4; M = Ag, X = SbF6) were formed, where the calixarene ligands adopt a 1,3‐alternate structure and the metal ions are coordinated linearly by the two pyrazolyl donors. [CuH2(bpzCal)]BF4 displayed a – for copper(I) complexes – unusual stability towards O2, which is due to the steric protection of the CuI center. By contrast a dinuclear copper(I) complex [Cu2(bpzCal)] that was obtained through treatment of [H2(bpzCal)] with two equivalents of Cu(HMDS) is rather sensitive towards O2. The preparation of a gold complex required the employment of a gold precursor, which contains one labile and one stabilizing neutral ligand, namely [(PPh3)Au(NCMe)]SbF6, which led to the formation of [(PPh3)AuH2(bpzCal)]SbF6. In this complex [H2(bpzCal)] acts only as a monodentate ligand for the gold center. Taken together, the results demonstrate the potential of [H2(bpzCal)] in providing rather different coordination spheres for metal ions.

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“…[H 2 (bpzCal)], [8] [Cu(HMDS)] 4 [9] and [(PPh 3 )Au(MeCN)]SbF 6 [10] were prepared according to literature procedures.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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The Coordination Behavior of Oxygen‐depleted Calixarenes towards d¹⁰ Noble Metal Ions

Keck

Hoof

Rawat

et al. 2020

Zeitschrift anorg allge chemie

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“…We were interested in exploiting calixarene‐shaped binding sites also in bioinorganic investigations, which required the introduction of soft donor atoms directly in place of one or more oxygen atoms of the calixarene lower rim. Recently, some of us have developed the oxygen‐depleted calixarene bispyrazolyl‐ tert ‐butyl‐calix[4]arene ([H 2 (bpzCal)], Figure ) featuring two pyrazole moieties beside two phenolic donors, which is reminiscent of a His 2 –Tyr 2 coordination sphere found in certain enzymes. One of those is the galactose oxidase (GO) and hence we decided to test the potential of the [bpzCal] 2− ligand to construct molecular models of the GO.…”

Section: Figurementioning

confidence: 99%

“… Left: Molecular structure of [H 2 (bpzCal)] . Right: Similarities of the ligand's donors with natural amino acid side chains.…”

Section: Figurementioning

confidence: 99%

Oxygen‐Depleted Calixarenes as Ligands for Molecular Models of Galactose Oxidase

Keck

Hoof

Herwig

et al. 2019

Chemistry A European J

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A calix[4]arene ligand, in which two of the phenol functions are replaced by pyrazole units has been employed to mimic the His2–Tyr2 (His: histidine, Tyr: tyrosine) ligand sphere within the active site of the galactose oxidase (GO). The calixarene backbone forces the corresponding copper(II) complex into a see‐saw‐type structure, which is hitherto unprecedented in GO modelling chemistry. It undergoes a one‐electron oxidation that is centered at the phenolate donor leading to a copper‐coordinated phenoxyl radical like in the GO. Accordingly, the complex was tested as a functional model and indeed proved capable of oxidizing benzyl alcohol to the respective aldehyde using two phenoxyl‐radical equivalents as oxidants. Finally, the results show that the calixarene platform can be utilized to arrange donor functions to biomimetic binding pockets that allow for the creation of novel types of model compounds.

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Synthesis, Structure and Magnetic Properties of Some Copper(II) Complexes Supported by Pendant Calix[4]arene Ligands

Jäschke,

Kischel,

Börner

et al. 2023

Eur J Inorg Chem

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The synthesis and characterization of three new calix[4]arene ligands bearing two pendant acylhydrazone arms and some of their Cu2+ complexes, namely [Cu(L1‐2H)(MeOH)] (3), [Cu(L1ꞌ‐H)(Cl)(2‐hydroxy‐1‐naphthaldehyde)] (4), [Cu2(L2‐2H)2] (5) and [Cu4(L3‐2H)2(OH)2(ClO4)2] (6) are described. The ligands are obtained by simple imine condensation reactions between calix[4]arene‐1,3‐bis‐acyl‐hydrazides and the corresponding carbaldehydes. The Cu2+ ions are always situated in 5‐membered chelate rings, either in a deprotonated −O−CR=N−N=CHR (enolate) or a neutral O=CR−NH−N=CHR (keto) form. In 3 and 4 a 5‐membered chelate ring is formed through interaction of the Cu2+ ion with the naphtholato group. Additional MeOH, chlorido or naphthaldehyde ligands complete the planar (3) or square pyramidal (4) coordination spheres. The thiophenes in 5 do not interact with the Cu2+ ions and dimerization of [CuL] entities occurs to produce centrosymmetric 2:2 complexes with four‐coordinated Cu2+ ions. In 6, two dinuclear [Cu2(L3‐2H)(OH)] subunits are connected by μ1,3‐bridging ClO4− ions. The magnetic properties of polycrystalline samples of 5 and 6 were studied by variable temperature magnetic susceptibility measurements. The χ′′(T) vs T plots indicate antiferromagnetic exchange interactions. The exchange interactions in 6 (J = −4.8 cm‐1) were found to be stronger than in 5 (J = −0.54 cm‐1). This is also supported by broken symmetry DFT calculations.

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Straightforward synthesis and catalytic applications of rigid N,O-type calixarene ligands

Cited by 15 publications

References 57 publications

The Coordination Behavior of Oxygen‐depleted Calixarenes towards d¹⁰ Noble Metal Ions

The Coordination Behavior of Oxygen‐depleted Calixarenes towards d¹⁰ Noble Metal Ions

Oxygen‐Depleted Calixarenes as Ligands for Molecular Models of Galactose Oxidase

Synthesis, Structure and Magnetic Properties of Some Copper(II) Complexes Supported by Pendant Calix[4]arene Ligands

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Straightforward synthesis and catalytic applications of rigid N,O-type calixarene ligands

Cited by 15 publications

References 57 publications

The Coordination Behavior of Oxygen‐depleted Calixarenes towards d10 Noble Metal Ions

The Coordination Behavior of Oxygen‐depleted Calixarenes towards d10 Noble Metal Ions

Oxygen‐Depleted Calixarenes as Ligands for Molecular Models of Galactose Oxidase

Synthesis, Structure and Magnetic Properties of Some Copper(II) Complexes Supported by Pendant Calix[4]arene Ligands

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The Coordination Behavior of Oxygen‐depleted Calixarenes towards d¹⁰ Noble Metal Ions

The Coordination Behavior of Oxygen‐depleted Calixarenes towards d¹⁰ Noble Metal Ions