| 1. |
- Blom, Magnus, et al.
(författare)
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Photomodulable bis-porphyrin molecular tweezers as dynamic host systems for diamine guests
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Bisporphyrin molecular tweezers with an enediyne (1) or a stiff stilbene (2) photoswitchable spacer are proposed as systems for modulation of bitopic binding to diamine guests via E/Z photoisomerization. The photoisomerization has been monitored by UV-Vis and 1H NMR spectroscopy and occurs without side reactions such as Bergman cyclization. Possible applications are rationalized in terms of competitive binding involving monoamine/diamine mixtures, and are supported by conformational analysis of the envisioned host-guest complexes. Binding dynamics for conformationally flexible guests show significantly different performance of aliphatic 1,w-diamine guests with varying N-N distance.
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| 2. |
- Blom, Magnus, 1984-, et al.
(författare)
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Synthesis and Properties of Bis-Porphyrin Molecular Tweezers : Effects of Spacer Flexibility on Binding and Supramolecular Chirogenesis
- 2016
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Ingår i: Molecules. - : MDPI AG. - 1431-5157 .- 1420-3049. ; 21:1
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Tidskriftsartikel (refereegranskat)abstract
- Abstract: Ditopic binding of various dinitrogen compounds to three bisporphyrin molecular tweezers with spacers of varying conformational rigidity, incorporating the planar ene-diyne (1), the helical stiff stilbene (2), or the semirigid glycoluril motif fused to the porphyrins (3) are compared. Binding constants Ka = 10^4 to 10^6 M^-1 reveal subtle differences between these tweezers, that are discussed in terms of porphyrin dislocation modes. Exciton coupled circular dichroism (ECCD) of complexes with chiral dinitrogen guests provides experimental evidence for the conformational properties of the tweezers. The results are further supported and rationalized by conformational analysis.
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| 3. |
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| 4. |
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| 5. |
- Canosa, Elyse, et al.
(författare)
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Strategies for Pollutant Monitoring in Museum Environments
- 2019
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Denna rapport beskriver metoder att undersöka och övervaka luftföroreningar inomhus i en museimiljö. Luftföroreningar i en museimiljö kan komma utifrån, från konstruktionsmaterial inomhus eller från museiföremålen själva. Dessa luftföroreningar kan orsaka skador på föremål genom att påskynda den kemiska nedbrytningen och orsaka till exempel försprödning, korrosion, missfärgning och sprickbildning. Skadliga luftföroreningar kan förekomma både i stora utrymmen som utställningssalar, eller i små täta utrymmen som montrar och förvaringslådor.
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| 6. |
- Hamnevik, Emil, et al.
(författare)
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Kinetic characterization of Rhodococcus ruber DSM 44541 alcohol dehydrogenase A
- 2014
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Ingår i: Journal of Molecular Catalysis B. - : Elsevier BV. - 1381-1177 .- 1873-3158. ; 99, s. 68-78
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Tidskriftsartikel (refereegranskat)abstract
- An increasing interest in biocatalysis and the use of stereoselective alcohol dehydrogenases in synthetic asymmetric catalysis motivates detailed studies of potentially useful enzymes such as alcohol dehydrogenase A (ADH-A) from Rhodococcus ruber. This enzyme is capable of catalyzing enantio-, and regioselective production of phenyl-substituted α-hydroxy ketones (acyloins) which are precursors for the synthesis of a range of biologically active compounds. In this study, we have determined the enzyme activity for a selection of phenyl-substituted vicinal diols and other aryl- or alkyl-substituted alcohols and ketones. In addition, the kinetic mechanism for the oxidation of (R)- and (S)-1-phenylethanol and the reduction of acetophenone has been identified as an Iso Theorell-Chance (hit and run) mechanism with conformational changes of the enzyme-coenzyme binary complexes as rate-determining for the oxidation of (S)-1-phenylethanol and the reduction of acetophenone. The underlying cause of the 270-fold enantiopreference for the (S)-enantiomer of 1-phenylethanol has been attributed to non-productive binding of the R-enantiomer. We have also shown that it is possible to tune the direction of the redox chemistry by adjusting pH with the oxidative reaction being favored at pH values above 7.
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| 7. |
- Norrehed, Sara, 1982-, et al.
(författare)
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Conformational restriction of flexible molecules in solution by a semirigid bis-porphyrin molecular tweezer
- 2013
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Ingår i: Tetrahedron. - : Elsevier BV. - 0040-4020 .- 1464-5416. ; 69:34, s. 7131-7138
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Norrehed, Sara, 1982-, et al.
(författare)
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Formation of persistent organic diradicals from N,N'-diphenyl-3,7- diazacyclooctanes
- 2019
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Ingår i: Monatshefte fuer Chemie. - Vienna : Springer. - 0026-9247 .- 1434-4475. ; 150:1, s. 77-84
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Tidskriftsartikel (refereegranskat)abstract
- N,N'-Diphenyl-3,7-diazacyclooctane and structurally related N,N'-diphenylbispidine derivatives react with silver(I) ions in a high-yielding C–C coupling reaction to produce dication–diradical species, with the silver ions serving a double function both as template and as an oxidant. The resulting bis(benzidino)phane derivatives are persistent organic radicals, stable for several months in solution as well as in the solid state, at room temperature and above, as well as being exposed to the atmosphere. The molecular structure features a double-decker cyclophane motif, stabilized by intramolecular π-dimerization of two delocalized benzidinium radical segments. Intermolecular π-dimers are formed in the solid state.
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| 9. |
- Norrehed, Sara, 1982-, et al.
(författare)
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Improved stereochemical analysis of conformationally flexible diamines by binding to a bisporphyrin molecular clip
- 2013
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:43, s. 14631-14638
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Tidskriftsartikel (refereegranskat)abstract
- The relative stereochemistry of acyclic diamines with several stereogenic centers has been analyzed by NMR spectroscopy in combination with conformational deconvolution. Binding to a bisporphyrin molecular clip improves the stereochemical assignment significantly. The diamines were synthesized from inexpensive sugar alcohols, and their stable hydrochlorides were quantitatively converted into free bases by treatment with ion-exchange resin.
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| 10. |
- Norrehed, Sara, 1982-
(författare)
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Modulation of Molecular Properties : Host–Guest Interactions for Structural Analysis and Chemical Reactions
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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