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Conformational restriction of flexible molecules in solution by a semirigid bis-porphyrin molecular tweezer
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.
Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC.ORCID iD: 0000-0002-9092-261X
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2013 (English)In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 69, no 34, 7131-7138 p.Article in journal (Refereed) Published
Abstract [en]

A semirigid bis-porphyrin molecular clip with a glycoluril backbone has been synthesized. The clip provides an adaptable molecular cavity for binding of diamines. Binding constants for diamines of 104–107 M−1 are orders of magnitude higher than those for monoamines of 103 M−1, indicating a preference to bidentate binding. NMR studies confirmed that binding of bidentate guests occurs inside the clip. Short- and medium-size acyclic molecular guests are locked into a single, extended conformation, and also guests with longer flexible chains exhibit considerably less conformational mobility than when free in solution. The size of the cavity adapts to the guest size, as indicated by modelling studies and self diffusion constants of the complexes.

Place, publisher, year, edition, pages
2013. Vol. 69, no 34, 7131-7138 p.
Keyword [en]
Conformational analysis, NMR spectroscopy, Hosteguest systems, Supramolecular chemistry, Porphyrinoids
National Category
Natural Sciences Organic Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-206036DOI: 10.1016/j.tet.2013.06.013ISI: 000322098000027OAI: oai:DiVA.org:uu-206036DiVA: diva2:643288
Funder
Swedish Research Council
Available from: 2013-08-26 Created: 2013-08-26 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Modulation of Molecular Properties: Host–Guest Interactions for Structural Analysis and Chemical Reactions
Open this publication in new window or tab >>Modulation of Molecular Properties: Host–Guest Interactions for Structural Analysis and Chemical Reactions
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis concerns the construction, use and modulation of various host–guest systems, from small bispidines for binding of inorganic ions to bisporphyrin clips for supramolecular systems.

Small flexible molecules undergo fast conformational movements when in solution. These conformational movements generate time-averaged population-weighted chemical shifts, coupling constants and NOEs when analysed by NMR spectroscopy. A bisporphyrin clip was designed to be used as a host for restriction of conformational movements of small flexible molecules by ditopic metal-ligand binding. Based on conformational analysis in combination with NMR analysis of molecular flexibility in solution (NAMFIS), the relative stereochemistry of flexible alditol-derived diamines containing three or four consecutive stereocentres could be determined.

To further explore the idea of conformational deconvolution via host–guest binding, two flexible molecular tweezers with photoswitchable moieties were developed. Upon photoswitching cis/trans isomerisation facilitates the opening and closing of these bisporphyrin hosts. A guest molecule could then be exposed to a “catch and stretch” or “catch and release” effect. Preliminary studies have shown that photoisomerisation of the constructed systems is possible without photodecomposition and preliminary binding studies have been conducted.

Controlled modulation of molecular conformations is of interest especially if the conformational steering activates a unit working as a nucleator in a larger structure or facilitates a reaction. The protonation-triggered modulation of bispidine conformations has been investigated. In addition to previously reported conformations we have observed that upon diprotonation a bispidine derivative can be driven into the unusual boat-boat conformation.

Finally, the unexpected formation of persistent organic radicals with a cyclophane motif from the reaction of N,N´-diphenyl-1-5-diazacyclooctane and AgBF4 is described. Interestingly, these diradicals exhibit features such as intramolecular π-stacking without lateral displacement and also intramolecular spin pairing.

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. 61 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1070
Keyword
host-guest systems, conformational analysis, NMR spectroscopy, bispidines, porphyrins
National Category
Organic Chemistry
Research subject
Chemistry with specialization in Organic Chemistry
Identifiers
urn:nbn:se:uu:diva-207138 (URN)978-91-554-8747-8 (ISBN)
Public defence
2013-10-25, B41, BMC, Husargatan 3, Uppsala, 09:30 (English)
Opponent
Supervisors
Available from: 2013-10-03 Created: 2013-09-09 Last updated: 2014-01-23

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Norrehed, SaraGogoll, AdolfGrennberg, Helena

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