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Protonation-triggered Conformational Modulation of an N,N´‑Dialkylbispidine: First observation of the elusive boat-boat conformer
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC.
Uppsala universitet, Teknisk-naturvetenskapliga vetenskapsområdet, Kemiska sektionen, Institutionen för kemi - BMC, Syntetisk organisk kemi.ORCID-id: 0000-0002-9092-261X
2013 (Engelska)Ingår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 11, s. 6292-6299Artikel i tidskrift (Refereegranskat) Published
Fritextbeskrivning
Abstract [en]

Modulation of the solution conformations of N,N′-bis(benzhydryl)bispidine has been achieved by protonation. Conformers have been characterized by NMR spectroscopy using nuclear Overhauser effects and residual dipolar couplings. In contrast to the preference for the chair–chair conformation for the free base and the monoprotonated species, the diprotonated bispidine is revealed to exist as a mixture of chair–boat and boat–boat conformers. While boat–boat conformers of bispidines have previously not been detected, they are here observed to constitute up to 70% of the bispidine population.

Ort, förlag, år, upplaga, sidor
2013. Vol. 11, s. 6292-6299
Nationell ämneskategori
Naturvetenskap Organisk kemi
Forskningsämne
Organisk kemi
Identifikatorer
URN: urn:nbn:se:uu:diva-206042DOI: 10.1039/c3ob41122bISI: 000324507100010OAI: oai:DiVA.org:uu-206042DiVA, id: diva2:643295
Forskningsfinansiär
VetenskapsrådetTillgänglig från: 2013-08-26 Skapad: 2013-08-26 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Ingår i avhandling
1. Modulation of Molecular Properties: Host–Guest Interactions for Structural Analysis and Chemical Reactions
Öppna denna publikation i ny flik eller fönster >>Modulation of Molecular Properties: Host–Guest Interactions for Structural Analysis and Chemical Reactions
2013 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
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.

 

Ort, förlag, år, upplaga, sidor
Uppsala: Acta Universitatis Upsaliensis, 2013. s. 61
Serie
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1070
Nyckelord
host-guest systems, conformational analysis, NMR spectroscopy, bispidines, porphyrins
Nationell ämneskategori
Organisk kemi
Forskningsämne
Kemi med inriktning mot organisk kemi
Identifikatorer
urn:nbn:se:uu:diva-207138 (URN)978-91-554-8747-8 (ISBN)
Disputation
2013-10-25, B41, BMC, Husargatan 3, Uppsala, 09:30 (Engelska)
Opponent
Handledare
Tillgänglig från: 2013-10-03 Skapad: 2013-09-09 Senast uppdaterad: 2014-01-23

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Norrehed, SaraGogoll, Adolf

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Organic and biomolecular chemistry
NaturvetenskapOrganisk kemi

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