Study on the Influence of Chirality in the Threading of Calix[6]arene Hosts with Dialkylammonium Axles

Talotta, Carmen; Concilio, Gerardo; Sala, Paolo Della; Gaeta, Carmine; Schalley, Christoph A.; Neri, Placido

doi:10.3390/molecules25225323

Cited by 3 publications

(10 citation statements)

References 49 publications

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“…Previously [28] we showed that in the presence of chiral calix [6]arene derivative 4 (Figure 1) the chiral (α-methyl-benzyl)benzylammonium axle 2 + forms the (endo-chiral)-2 + @4 pseudorotaxane diastereoisomer (Figure 1) in which the calix-cavity prefers to host the α-methyl-benzyl group with respect to the simple unsubstituted benzyl group as in (exo-chiral)-2 + @4. DFT calculations suggested that, in addition to the fundamental Hbonding N-H .…”

Section: Resultsmentioning

confidence: 96%

“…: 4) bearing classical stereogenic centers. In particular, we observed that the threading of chiral calix [6]arene 4 with chiral directional (α-methylbenzyl)benzylammonium axle 2 + occurs with an endo-α-methyl-benzyl preference [28]. In detail, the threading between 4 and 2 + led to the stereoselective formation of (endo-chiral)-2 + @4.…”

Section: Methodsmentioning

confidence: 92%

“…More recently, the formation of calixarene-based chiral pseudorotaxanes (e.g. : (endochiral)-2 + @4 in Figure 1) has been investigated by us [28], exploiting cationic axles (e.g. : 2 + ) and calix [6]-wheels (e.g.…”

Section: Methodsmentioning

confidence: 99%

“…The synthesis of hexamethoxycalix [6]arene 3 [14b] and (S)-(α-methyl-benzyl) benzylammonium axle 2 + as barfate salt [28] were performed as previously described in the literature. [2]Rotaxane (Endo-Chiral)-2 + @ 3 1D and 2D NMR experiments.…”

Section: Synthesis and Characterization Of Hexamethoxycalixmentioning

confidence: 99%

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Chirality Transfer in a Calixarene-Based Directional Pseudorotaxane Complex

Concilio¹,

Gaeta²,

Sala³

et al. 2021

Chemistry

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Hexamethoxycalix[6]arene 3 forms a directional pseudorotaxane complex with the chiral axle (S)-(α-methyl-benzyl)benzylammonium 2+. Between the two (endo-chiral)-2+@3 and (exo-chiral)-2+@3 pseudorotaxane stereoisomers, the former is preferentially formed. This result confirms the validity of the “endo-α-methyl-benzyl rule”, previously reported by us. DFT calculations suggest that C-H···π interactions between the methyl group of 2+ and the calixarene aromatic rings, determine the stereoselectivity of the threading process toward the “endo-α-methyl-benzyl preference”. An amplification of optical rotation is observed upon formation of the pseudorotaxane complex (endo-chiral)-2+@3 with respect to free axle 2+. Thus, the specifical rotation of the 1:1 mixture of chiral 2+∙B(ArF)4− salt and achiral 3 was augmented upon formation of the pseudorotaxane and DFT calculations were used to rationalize this result.

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Section: Resultsmentioning

confidence: 96%

Section: Methodsmentioning

confidence: 92%

Section: Methodsmentioning

confidence: 99%

Section: Synthesis and Characterization Of Hexamethoxycalixmentioning

confidence: 99%

See 2 more Smart Citations

Chirality Transfer in a Calixarene-Based Directional Pseudorotaxane Complex

Concilio¹,

Gaeta²,

Sala³

et al. 2021

Chemistry

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“…Consequently, in an organic solvent, ammonium cations and barfate anion give very loose ion pairs originating free “naked” organic cations. 17 , 19 …”

Section: Resultsmentioning

confidence: 99%

Chromogenic Properties of p-Pyridinium- and p-Viologen-Calixarenes and Their Cation-Sensing Abilities

et al. 2021

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The synthesis of calix[4]- and -[6]arene derivatives P6 (H) 2 2+ ·(Cl – ) 2 , V4 (H) 2 4+ ·(Cl – ) 2 ·(I – ) 2 , and V6 (H) 2 4+ ·(Cl – ) 2 ·(I – ) 2 bearing N -linked pyridinium ( P ) and viologen ( V ) units at the upper rim is described here. A rare example of an anionic conformational template is reported for p -pyridiniumcalix[6]arene P6 (H) 2 2+ , which adopts a 1,3,5-alternate conformation in the presence of chloride anions. Derivatives P6 (H) 2 2+ ·(Cl – ) 2 , V6 (H) 2 4+ ·(Cl – ) 2 ·(I – ) 2 , and V4 (H) 2 4+ ·(Cl – ) 2 ·(I – ) 2 show a negative solvatochromism, while their UV–vis acid–base titration evidenced that upon addition of a base, new bands appear at 487, 583, and 686 nm, respectively, due to the formation of betainic monodeprotonated species P6 (H) 1 + , V6 (H) 1 3+ , and V4 (H) 1 3+ . These new bands were attributable to the intramolecular charge-transfer (CT) transition from the phenoxide to the pyridinium or viologen moiety and were responsive to the presence of cations. In fact, the band at 487 nm of P6 (H) 1 + was quenched in the presence of a hard Li + cation, and the color of its acetonitrile solution was changed from pink to colorless upon addition of LiI. Consequently, this derivative can be considered as a useful host for the recognition and sensing of lithium cations.

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Skeletal Editing of Mechanically Interlocked Molecules: Nitrogen Atom Deletion from Crown Ether-Dibenzylammonium Rotaxanes

Gauthier,

Whittingham,

Hasija

et al. 2024

J. Am. Chem. Soc.

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Removing the nitrogen atom from secondary amines while simultaneously linking the remaining fragments is a powerful form of late-stage skeletal editing. Here, we report its use for the deletion of the nitrogen atom of the dibenzylammonium template used to assemble crown ether rotaxanes. The reaction uses an anomeric amide that activates secondary amines to generate a carbon−carbon bond that replaces the amine nitrogen. Despite the potential for dethreading of the intermediate diradical pair, the nitrogen atom was successfully deleted from a series of rotaxane axles as long as the macrocycle could access coconformations that did not inhibit the reaction of the amine group. The skeletally edited interlocked molecules were obtained directly from the parent crown ether-dibenzylammonium rotaxanes in modest yields (23−36%) and characterized by NMR spectroscopy, mass spectrometry, and X-ray crystallography. One skeletally edited rotaxane shows a network of weak CH•••O hydrogen bonds between the crown ether and benzylic methylene groups of the axle in the solid state, in place of the crown etherammonium binding motif used to assemble the parent, unedited, rotaxane.

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Study on the Influence of Chirality in the Threading of Calix[6]arene Hosts with Dialkylammonium Axles

Cited by 3 publications

References 49 publications

Chirality Transfer in a Calixarene-Based Directional Pseudorotaxane Complex

Chirality Transfer in a Calixarene-Based Directional Pseudorotaxane Complex

Chromogenic Properties of p-Pyridinium- and p-Viologen-Calixarenes and Their Cation-Sensing Abilities

Skeletal Editing of Mechanically Interlocked Molecules: Nitrogen Atom Deletion from Crown Ether-Dibenzylammonium Rotaxanes

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