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Chloromethane Complexation by Cryptophanes: Host-Guest Chemistry Investigated by NMR and Quantum Chemical Calculations
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
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 [en]
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: urn:nbn:se:su:diva-81472ISBN: 978-91-7447-598-2 (print)OAI: oai:DiVA.org:su-81472DiVA: diva2:561864
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
List of papers
1. Inclusion complexes of cryptophane–E with dichloromethane and chloroform: A thermodynamic and kinetic study using the 1D-EXSY NMR method
Open this publication in new window or tab >>Inclusion complexes of cryptophane–E with dichloromethane and chloroform: A thermodynamic and kinetic study using the 1D-EXSY NMR method
2008 (English)In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 46, no 12, 1135-1140 p.Article in journal (Refereed) Published
Abstract [en]

Complexation equilibria and kinetics of exchange of chloroform and dichloromethane molecules between the cavity of cryptophane-E and bulk solution were investigated using NMR methods. Using one dimensional magnetization transfer (1D-EXSY type sequence), chemical exchange rates were measured in different temperature ranges, limited by the equilibrium constant values of the complexes and the boiling points of the guest substances. From the kinetic data, activation energies were calculated using the Arrhenius equation. From the temperature dependence of the association constant data, the enthalpy and entropy of complexation were estimated and compared with values for similar complexes of other cryptophanes.

Keyword
proton NMR, inclusion complexes, complexation kinetics, complexation thermodynamics
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-15164 (URN)10.1002/mrc.2327 (DOI)000261163000007 ()
Available from: 2008-11-23 Created: 2008-11-23 Last updated: 2012-10-24Bibliographically approved
2. NMR Investigation of Guest–Host Complex between Chloroform and Cryptophane C
Open this publication in new window or tab >>NMR Investigation of Guest–Host Complex between Chloroform and Cryptophane C
Show others...
2010 (English)In: Magnetic Resonance in Chemistry, ISSN 0749-1581, E-ISSN 1097-458X, Vol. 48, no 8, 623-629 p.Article in journal (Refereed) Published
Abstract [en]

Guest–host complex between cryptophane C, possessing two non-equivalent caps, and chloroform is investigated by NMR spectroscopy. The kinetics of the chloroform exchange between the bound and free sites is determined by 1H exchange spectroscopy. Moreover, the preferential orientation of chloroform molecule with respect to the cryptophane C frame is examined by the NOESY and ROESY experiments. The experimental findings are compared to the results of quantum chemical calculations.

Keyword
proton NMR, inclusion complexes, complexation kinetics, cross-relaxation
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-81422 (URN)10.1002/mrc.2637 (DOI)000280218800008 ()
Available from: 2012-10-19 Created: 2012-10-19 Last updated: 2017-12-07Bibliographically approved
3. Inclusion of Chloromethane Guests Affects Conformation and Internal Dynamics of Cryptophane-D Host
Open this publication in new window or tab >>Inclusion of Chloromethane Guests Affects Conformation and Internal Dynamics of Cryptophane-D Host
Show others...
2012 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 116, no 27, 7898-7913 p.Article in journal (Refereed) Published
Abstract [en]

Cryptophane-D is composed of two nonequivalent cyclotribenzylene caps bound together by three OCH2CH2O bridges in a syn arrangement. Host-guest complexes with chloroform and dichloromethane were investigated in solution by NMR spectroscopy. Variable temperature NMR. H-1 and C-13 spectra showed effects of chemical exchange between the free and bound guest and of conformational exchange for the host, strongly and specifically affected by guest binding. We found in particular that the carbon-13 chemical shifts for the linkers connecting the two cyclotribenzylene units are very informative. The NMR results were supported by DFT calculations. The guest exchange was also studied quantitatively, either by EXSY measurements (for chloroform as guest) or by line-shape analysis (for dichloromethane as guest). In the case of chloroform guest, we also investigated cross relaxation between the guest and host protons, as well as carbon 13 longitudinal relaxation and heteronuclear NOE at three different fields. The results were interpreted in terms of orientation and dynamics of the guest inside the host cavity. Putting together various types of evidence resulted in remarkably detailed insight into the process of molecular recognition of the two guests by cryptophane-D host.

National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-80433 (URN)10.1021/jp303469x (DOI)000306264200016 ()
Note

AuthorCount:6;

Available from: 2012-09-24 Created: 2012-09-19 Last updated: 2017-12-07Bibliographically approved
4. Host-Guest Complexes between Cryptophane-C and Chloromethanes Revisited
Open this publication in new window or tab >>Host-Guest Complexes between Cryptophane-C and Chloromethanes Revisited
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.

Keyword
inclusion complexes, complexation kinetics, cross relaxation
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-92050 (URN)10.1002/mrc.3898 (DOI)000319965700005 ()
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
5. Chloromethane complexes of cryptophane-A and its analogue with butoxy groups
Open this publication in new window or tab >>Chloromethane complexes of cryptophane-A and its analogue with butoxy groups
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Host-guest complexes between cryptophane-A as host and dichloromethane and chloroformas guests are investigated using 1H and13C NMR spectroscopy. Moreover, a relatedcryptophane, with the methoxy groups replaced by butoxy units (cryptophane-But), and itscomplexes with the same guests were also studied. Variable temperature spectra showedeffects of chemical exchange between the free and bound guests, as well as of conformationalexchange of the host. The guest exchange was studied quantitatively by exchangespectroscopy or line shape analysis. In the case of CHCl3@cryptophane-A, carbon-13relaxation of the guest was also investigated. Structural information was obtained throughmeasurements of cross-relaxation rates, both within the host and between the host and guestprotons. The NMR results were supported by DFT calculations.1

National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
urn:nbn:se:su:diva-81426 (URN)
Available from: 2012-10-19 Created: 2012-10-19 Last updated: 2012-10-24Bibliographically approved

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