Stereochemical dynamics of crown ethers: Ring inversion in isomeric dicyclohexano-18-crown-6 systems as studied by 13C magnetic resonance at low temperature

Buchanan, G. W.; Bourque, K.; Bovenkamp, John W.; Rodrigue, André; Bannard, R. A. B.

doi:10.1016/0040-4039(84)80041-6

Cited by 21 publications

(10 citation statements)

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“…DC-18-crown-6 (A) forms a complex (16) with a 1:2 host:guest ratio with NaOPh as compared with the 1: 1 ratio of its potassium analogue (6). The crystal structure of 16 has been determined (19) and differs considerably from that of DC-18-crown-6 (B).2KOPh (8).…”

Section: Resultsmentioning

confidence: 99%

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Complexes of 18-crown-6 macrocyclic ethers obtained from ethereal solvents. Complexes of potassium and sodium salts with host:guest ratios of 1:2 and 1:3

Rodrigue¹,

Bovenkamp²,

Lacroix³

et al. 1986

Can. J. Chem.

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This paper describes the synthesis, in ethereal solvents, of the complexes of 18-crown-6, the cis-syn-cis and the cis-anti-cis isomers of dicyclohexano-18-crown-6, and dibenzo-18-crown-6 with the potassium and sodium salts of phenoxide and thiocyanate (as well as some potassium oximate salts). In general, the macrocycles break down the aggregates of the potassium salts so that the complexes of the contact ion pairs are isolated. The complex of the cis-anti-cis isomer of dicyclohexano-18-crown-6, however, which has a low stability constant, complexes the dimer of potassium phenoxide to give a complex with a 1:2 host:guest ratio. This appears to be the first example of a 1:2 host:guest ratio of a potassium salt with an 18-crown-6 macrocycle. There is a greater tendency for the complexes of sodium salts to have host:guest ratios less than 1:l. Thus, 18-crown-6 gives complexes with sodium phenoxide and sodium thiocyanate which have 1:3 and 1:2 host:guest ratios, respectively. Host:guest ratios of 1 :2 are also obtained for the two above-mentioned isomers of dicyclohexano-18-crown-6 and for dibenzo-18-crown-6 with sodium phenoxide. Sodium thiocyanate gives complexes with either 1: 1 or 1:2 host:guest ratios depending on the macrocycle. With dibenzo-18-crown-6, sodium thiocyanate gives a 1: 1 complex in which one molecule of the solvent used is incorporated into the complex. The infrared and ultraviolet spectra of the complexes are discussed.

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Section: Resultsmentioning

confidence: 99%

“…Recently, we have carried out low temperature 13C nmr stereochemical studies of the cis-syn-cis and cis-anti-cis isomers (isomers A and B, respectively) of dicyclohexano-18-crown-6 (6,7). During our work with these compounds, it 'Author to whom correspondence should be addressed.…”

Section: Introductionmentioning

confidence: 99%

Complexes of 18-crown-6 macrocyclic ethers obtained from ethereal solvents. Complexes of potassium and sodium salts with host:guest ratios of 1:2 and 1:3

Rodrigue¹,

Bovenkamp²,

Lacroix³

et al. 1986

Can. J. Chem.

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“…It is important to note that the I3C chemical shifts of both major and minor conformations of 1 and 2 at 173 K are, on the average, within 1 pprn of those for the potassium phenoxide complexes at comparable temperatures (2). This suggests that there are no major structural perturbations from the "all gauche-0-CH2-CH2-0'' geometry in either of the conformations of free 1 and 2.…”

Section: Results and Discussion (I) Spectramentioning

confidence: 98%

“…In our communication (2) it was noted that 50.3-MHz I3C spectra of pure 1 and 2, but not the potassium complexes, showed evidence of additional spectral features at very low temperatures. The inherent sensitivity of the instrument used, however, did not permit a clear definition of the phenomena involved.…”

Section: Introductionmentioning

confidence: 99%

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Novel stereochemical equilibria in crown ethers. Detection of additional conformations of cis-syn-cis- and cis-anti-cis-dicyclohexano-18-crown-6 by 100.6-MHz ¹³C nuclear magnetic resonance at 173 K

Buchanan¹,

Bourque²,

Bovenkamp³

et al. 1985

Can. J. Chem.

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High field I3C nmr has been utilized for the analysis of new conformational equilibria in each of the title crown ethers at low temperature. Evidence indicates that these equilibria arise from restricted rotation in the macrocyclic portions of these molecules. The conformational free energy differences between the isomers are small (0.1-0.3 kcal/mol) while baniers to their interconversion are of the order of 8.5-9.0 kcal/mol. Comparisons are made with the degenerate equilibria involving inversion of the cyclohexane rings. Chem. 63, 2747Chem. 63, (1985. On a fait appel la rmn du I3C 2 haut champ pour analyser de nouveaux Cquilibres conformationnels, a basse temperature, IntroductionBoth the cis-syn-cis (1) and cis-anti-cis (2) isomers of dicyclohexano-18-crown-6 (below) are expected to undergo degenerate inversions of their 18-membered rings, which necessarily involve inversion of their cyclohexane rings (1).

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Molecular Signal Transduction by Conformational Transmission: Use of Tetrasubstituted Perhydroanthracenes as Transducers

Weinig¹,

Krauss²,

Seydack³

et al. 2001

Chem. Eur. J.

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2,3,6,7-Tetrasubstituted cis-anti-cis perhydroanthracenes have been studied as conformational transducers for molecular signal transduction. 2,2'-Bipyridine groups attached to the perhydroanthracene through ether linkages were chosen as receptor substituents, while pyrene groups were selected as effectors. A chelation-induced triple ring flip of the perhydroanthracene could be achieved by the complexation of zinc(II) ions at the bipyridine sites of ligands 13 and 15. It was found that two pyrene substituents attached to the perhydroanthracene via a linker with an E double bond and an ester group could be used to monitor the triple ring flip. In the equatorial positions, the pyrenes are sufficiently close to form an excimer in the excited state, giving a fluorescence signal at 480 nm. In the axial positions, they are far away from each other and give mainly a monomer fluorescence signal at 380 nm. Both the bipyridine receptor and the pyrene effector are present in compound 33. The conformational switching 34-->35 (the two conformers of 33) has successfully been used for a signal transduction over a signal distance of 2 nm.

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Stereochemical dynamics of crown ethers: Ring inversion in isomeric dicyclohexano-18-crown-6 systems as studied by 13C magnetic resonance at low temperature

Cited by 21 publications

References 4 publications

Complexes of 18-crown-6 macrocyclic ethers obtained from ethereal solvents. Complexes of potassium and sodium salts with host:guest ratios of 1:2 and 1:3

Complexes of 18-crown-6 macrocyclic ethers obtained from ethereal solvents. Complexes of potassium and sodium salts with host:guest ratios of 1:2 and 1:3

Novel stereochemical equilibria in crown ethers. Detection of additional conformations of cis-syn-cis- and cis-anti-cis-dicyclohexano-18-crown-6 by 100.6-MHz ¹³C nuclear magnetic resonance at 173 K

Molecular Signal Transduction by Conformational Transmission: Use of Tetrasubstituted Perhydroanthracenes as Transducers

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Stereochemical dynamics of crown ethers: Ring inversion in isomeric dicyclohexano-18-crown-6 systems as studied by 13C magnetic resonance at low temperature

Cited by 21 publications

References 4 publications

Complexes of 18-crown-6 macrocyclic ethers obtained from ethereal solvents. Complexes of potassium and sodium salts with host:guest ratios of 1:2 and 1:3

Complexes of 18-crown-6 macrocyclic ethers obtained from ethereal solvents. Complexes of potassium and sodium salts with host:guest ratios of 1:2 and 1:3

Novel stereochemical equilibria in crown ethers. Detection of additional conformations of cis-syn-cis- and cis-anti-cis-dicyclohexano-18-crown-6 by 100.6-MHz 13C nuclear magnetic resonance at 173 K

Molecular Signal Transduction by Conformational Transmission: Use of Tetrasubstituted Perhydroanthracenes as Transducers

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Novel stereochemical equilibria in crown ethers. Detection of additional conformations of cis-syn-cis- and cis-anti-cis-dicyclohexano-18-crown-6 by 100.6-MHz ¹³C nuclear magnetic resonance at 173 K