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Host-Guest Complexes between Cryptophane-C and Chloromethanes Revisited
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Charles University Prague .
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
2013 (English)In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 51, no 1, 19-31 p.Article in journal (Refereed) Published
Abstract [en]

Cryptophane-C is composed of two nonequivalent cyclotribenzylene caps, one of which contains methoxy group substituents on the phenyl rings. The two caps are connected by three OCH2CH2O linkers in an anti arrangement. Host-guest complexes of cryptophane-C with dichloromethane and chloroform in solution were investigated in detail by nuclear magnetic resonance techniques and density functional theory (DFT) calculations. Variable temperature proton and carbon-13 spectra show a variety of dynamic processes, such as guest exchange and host conformational transitions. The guest exchange was studied quantitatively by exchange spectroscopy measurements or by line-shape analysis. The conformational preferences of the guest-containing host were interpreted through cross-relaxation measurements, providing evidence of the gauche+2 and gauche-2 conformations of the linkers. In addition, the mobility of the chloroform guest inside the cavity was studied by carbon-13 relaxation experiments. Combining different types of evidence led to a detailed picture of molecular recognition, interpreted in terms of conformational selection.

Place, publisher, year, edition, pages
2013. Vol. 51, no 1, 19-31 p.
Keyword [en]
inclusion complexes, complexation kinetics, cross relaxation
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-92050DOI: 10.1002/mrc.3898ISI: 000319965700005OAI: oai:DiVA.org:su-92050DiVA: diva2:636949
Funder
Swedish Research Council, 613-2011-3311Knut and Alice Wallenberg Foundation
Note

AuthorCount:6;

Available from: 2013-07-15 Created: 2013-07-15 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Chloromethane Complexation by Cryptophanes: Host-Guest Chemistry Investigated by NMR and Quantum Chemical Calculations
Open this publication in new window or tab >>Chloromethane Complexation by Cryptophanes: Host-Guest Chemistry Investigated by NMR and Quantum Chemical Calculations
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Host–guest complexes are widely investigated because of their importance in many industrial applications. The investigation of their physico–chemical properties helps understanding the inclusion phenomenon. The hosts investigated in this work are cryptophane molecules possessing a hydrophobic cavity. They can encapsulate small organic guests such as halo–methanes (CH2Cl2, CHCl3). The encapsulation process was investigated from both the guest and the host point of view. With the help of Nuclear Magnetic Resonance (NMR), the kinetics of complex formation was determined. The information was further used to obtain the activation energies of the processes. Having done this on five different cryptophanes, it is possible to relate the energies to structural differences between the hosts. Via the dipolar interaction between the guest’s and host’s protons, one can get information on the orientation of the guest inside the cavity. Moreover, the dynamics of the guest can be further investigated by its relaxation properties. This revealed restricted motion of the guest inside the host cavity. Not only the nature of the guest plays an important role. The host is also changing its properties upon encapsulation. All the cryptophanes investigated here can exchange rapidly between many conformers. These conformers have different–sized cavities. Quantum chemical optimization of the structure of the conformers makes volume estimation possible. Not only the cavity volumes, but also the quantum-chemically obtained energies and the calculated chemical shifts of the carbon–13 atoms can be helpful to follow the changes of the host upon complex formation. The host cannot be considered as a rigid entity. Analysis of variable temperature proton and carbon-13 spectra shows that the encapsulation can be considered as a mixture of conformational selection and induced fit. The structures of the formed complexes are further investigated by means of two-dimensional nuclear Overhauser spectroscopy (NOESY). The complex formation, its kinetics and thermodynamics are found to be a complicated function of structure elements of the host, the cavity size and the guest size and properties.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2012. 57 p.
Keyword
Host–guest complexes, inclusion phenomenon, cryptophanes, NMR, kinetics, activation energy, dipolar interaction, exchange, quantum chemical optimization, calculated chemical shifts, NOESY, cavity size
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-81472 (URN)978-91-7447-598-2 (ISBN)
Public defence
2012-11-30, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted. Paper 5: Manuscript.

 

Available from: 2012-11-08 Created: 2012-10-22 Last updated: 2013-08-23Bibliographically approved
2. Fast Dynamic Processes in Solution Studied by NMR Spectroscopy
Open this publication in new window or tab >>Fast Dynamic Processes in Solution Studied by NMR Spectroscopy
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nuclear magnetic resonance (NMR) spectroscopy is capable to deliver a detailed information about the dynamics on molecular level in a wide range of time scales, especially if accompanied by suitably chosen theoretical tools. In this work, we employed a set of high-resolution NMR techniques to investigate dynamics processes in several weakly interacting molecular systems in solution.

Van der Waals interactions play an important role in inclusion complexes of cryptophane-C with chloroform or dichloromethane. The complex formation was thoroughly investigated by means of 1H and 13C NMR experiments along with the quantum-chemical density functional theory (DFT) calculations. We characterized kinetics, thermodynamics, as well as fine details of structural rearrangements of the complex formation.

Internal dynamics of oligo- and polysaccharides presents a considerable challenge due to possible coupling of internal and global molecular motions. Two small oligosaccharides were investigated as test cases for a newly developed integrated approach for interpreting the dynamics of the molecules with non-trivial internal flexibility. The approach comprised advanced theoretical tools, including stochastic modeling, molecular dynamics (MD) simulations, and hydrodynamic simulations.

A biologically important bacterial O-antigenic polysaccharide from E. Coli O91 was addressed employing selective isotope labeling and multiple-field 13C relaxation experiments. The complex dynamics of the polysaccharide is characterized by the conformational motion of the exocyclic groups of the sugars, superimposed to the breathing motion of the polymeric chain.

Hydrogen bonding is another major non-covalent interaction. Dilute solutions of ethanol were chosen as a model of liquid systems containing extensive hydrogen-bonded networks. We developed a new methodology consisting of NMR diffusion measurements, DFT calculations, and hydrodynamic modeling and utilized it to determine average size of the molecular clusters of ethanol at given conditions.

Abstract [cs]

Nukleární magnetická rezonance (NMR) dokáže poskytnout detailní informace o dynamice na molekulární úrovni v širokém oboru časových škál, zejména pokud je doplněna vhodnými teoretickými nástroji. V této práci byla použita sada technik NMR spektroskopie vysokého rozlišení pro výzkum dynamických procesů slabě interagujících molekulárních struktur v roztoku.

Van der Waalsovy interakce hrají důležitou roli v inkluzních komplexech kryptofanu-C s chloroformem nebo dichlormethanem. Tvorba komplexu byla podrobně zkoumána za použití 1H a13C NMR experimentů spolu s kvantově-chemickými výpočty. Byla charakterizována kinetika, termodynamika, jakož i detaily strukturních změn při tvorbě komplexu.

Vnitřní dynamika oligo- a polysacharidů představuje velkou výzvu  kvůli možnému provázání lokálního a globálního molekulárního pohybu. Dva modelové oligosacharidy byly použity pro testování nově vyvinuté integrované metody pro popis dynamiky molekul s netriviální vnitřní flexibilitou. Tato metoda spojuje pokročilé teoretické výpočty včetně stochastického modelování, simulací molekulové dynamiky a hydrodynamiky.

Antigenní bakteriální polysacharid z E. Coli O91, důležitý z biologického hlediska, byl studován za pomoci selektivního izotopového značení a NMR relaxačních experimentů ve více magnetických polích. Komplexní dynamika polysacharidu je charakterizována konformačními změnami exocyklických skupin cukerných reziduí a omezenou interní flexibilitou polymerního řetězce.

Vodíkové vazby jsou další z důležitých nekovalentních interakcí. Zředěné roztoky ethanolu byly vybrány jako model kapalného systému obsahujícího rozsáhlou síť vodíkových vazeb. Vyvinuli jsme novou metodologii, složenou z NMR difúzních měření, kvantově-chemických výpočtů a hydrodynamického modelování a aplikovali ji pro zjištění průměrné velikosti molekulových klastrů ethanolu za specifických podmínek.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry, Stockholm University, 2013. 52 p.
Keyword
Nuclear magnetic resonance, Dynamics, Ethanol, Cryptophanes, Saccharides, Nukleární magnetická rezonance, dynamika, ethanol, kryptofan, sacharidy
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-92881 (URN)978-91-7447-741-2 (ISBN)
Public defence
2013-09-25, Magnéli Hall, Arrhenius Laboratory, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 4: Accepted. Paper 5: Manuscript.

Available from: 2013-09-03 Created: 2013-08-23 Last updated: 2013-08-26Bibliographically approved

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