NMR studies of chloroform@cryptophane-A and chloroform@bis-cryptophane inclusion complexes oriented in thermotropic liquid crystals

Chaffee, Kathleen E.; Marjańska, Małgorzata; Goodson, Boyd M.

doi:10.1016/j.ssnmr.2005.08.012

Cited by 6 publications

(4 citation statements)

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“…This work was extended to the study of CHCl 3 @ 1 and CHCl 3 @ 151 (bis-cryptophane described in section 4.4) complexes in a nematic thermotropic liquid crystal (ZLI 1132) at different temperatures . As previously observed by Goodson and co-workers, a larger 13 C−H dipolar coupling was observed in both complexes for the encapsulated chloroform molecule vs the free guest.…”

Section: Dynamics Of the Guest In The Cryptophane Cavitysupporting

confidence: 52%

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Cryptophanes and Their Complexes—Present and Future

2008

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Contents 98 4.2. Monofunctionalized Cryptophanes: Cryptophanol 98 4.3. Cryptophanes as Biosensors 99 4.4. Bis-cryptophanes 100 5. Structural Aspects and Characterization of Cryptophanes 100 5.1. Some Peculiarities in the Characterization of Cryptophane Hosts 101 5.2. Inverted and Imploded Cryptophanes 102 5.3. Molecular Structures of Cryptophane-A 1 and Related Ones 103 5.4. Some Aspects of Cryptophanes in the Crystalline State 104

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Section: Dynamics Of the Guest In The Cryptophane Cavitysupporting

confidence: 52%

“…Schematic representation of the CHCl 3 @cryptophane-A ( 1 ) complex oriented in a ZLI 1132 liquid crystal showing the average orientation of both free and bound chloroform (Reprinted from ref , Copyright 2006, with permission from Elsevier).…”

Section: Dynamics Of the Guest In The Cryptophane Cavitymentioning

confidence: 99%

Cryptophanes and Their Complexes—Present and Future

2008

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“…Finally, the investigation of complexation of other small neutral species by 1 (e.g., other noble gases, CO x , NO x , etc. ), as well as liquid-crystal NMR studies of such cryptophane host−guest interactions, , are ongoing and will be reported in due course.…”

Section: Discussionmentioning

confidence: 98%

Encapsulation of Small Gas Molecules by Cryptophane-111 in Organic Solution. 1. Size- and Shape-Selective Complexation of Simple Hydrocarbons

et al. 2009

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The reversible trapping of small hydrocarbons and other gases by cryptophane-111 (1) in organic solution was characterized with variable-temperature (1)H NMR spectroscopy. Characteristic spectral changes observed upon guest binding allowed kinetic and thermodynamic data to be readily extracted, permitting quantification and comparison of different host-guest interactions. Previous work (J. Am. Chem. Soc. 2007, 129, 10332) demonstrated that 1, the smallest cryptophane to date, forms a complex with xenon with remarkably high affinity. Presently, it is shown that 1 also exhibits slow exchange dynamics with methane at reduced temperatures (delta(bound) = -5.2 ppm) with an association constant K(a) = 148 M(-1) at 298 K. In contrast, ethane and ethylene are poorly recognized by 1 with K(a) values of only 2 M(-1) and 22 M(-1), respectively; moreover, chloromethane (whose molecular volume is similar to that of xenon, approximately 42 A(3)) is not observed to bind to 1. Separately, molecular hydrogen (H(2)) gas is observed to bind 1, but in contrast to other ligands presently studied, H(2) complexation is spectrally manifested by fast exchange throughout virtually the entire range of available conditions, as well as by a complex dependence of the guest (1)H resonance frequency upon temperature and host concentration. Taken together, these results establish 1 as a selective host for small gases, with implications for the design of size- and geometry-selective sensors targeted for various gas molecules.

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“…The difference between the Δσ(C) values reported in that study was rather small. In a more recent communication from the same group, Chaffee and co-workers reported Δσ( C ) = −37 ± 9 ppm for free chloroform in an LC solution, while Δσ( C ) = −54 ± 15 ppm was given for a chloroform molecule trapped inside the cryptophane-A cavity in the same LC system. Our present results for carbon CSA agree very well with these values.…”

Section: Resultsmentioning

confidence: 96%

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

2015

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The case of (13)C-labeled chloroform exchanging between a free site in solution and the encaged site within the cryptophane-D cavity is investigated using the measurements of longitudinal cross-correlated relaxation rates, involving the interference of the dipole-dipole and chemical shielding anisotropy interactions. A compact theoretical expression is provided, along with an experimental protocol, based on INEPT (insensitive nuclei enhanced by polarization)-enhanced double-quantum-filtered inversion recovery measurements. The analysis of the build-up curves results in a set of cross-correlated relaxation rates for both the (13)C and (1)H spins at the two sites. It is demonstrated that the results can be given a consistent interpretation in terms of molecular-level properties, such as rotational correlation times, the Lipari-Szabo order parameter, and interaction strength constants. The analysis yields the bound-site carbon-13 chemical shielding anisotropy, ΔσC = -58 ± 8 ppm, in good agreement with most recent liquid-crystal measurements and the corresponding proton shielding anisotropy, ΔσH = 14 ± 2 ppm.

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NMR studies of chloroform@cryptophane-A and chloroform@bis-cryptophane inclusion complexes oriented in thermotropic liquid crystals

Cited by 6 publications

References 41 publications

Cryptophanes and Their Complexes—Present and Future

Cryptophanes and Their Complexes—Present and Future

Encapsulation of Small Gas Molecules by Cryptophane-111 in Organic Solution. 1. Size- and Shape-Selective Complexation of Simple Hydrocarbons

Chemical Shielding Anisotropies for Chloroform Exchanging between a Free Site and a Complex with Cryptophane-D: A Cross-Correlated NMR Relaxation Study

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