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Racemisation dynamics of torsion angle restricted biphenyl push-pull cyclophanes

Rotzler, Jürgen and Gsellinger, Heiko and Neuburger, Markus and Vonlanthen, David and Häussinger, Daniel and Mayor, Marcel. (2011) Racemisation dynamics of torsion angle restricted biphenyl push-pull cyclophanes. Organic and Biomolecular Chemistry, 9 (1). pp. 86-91.

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Official URL: http://edoc.unibas.ch/dok/A5840852

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Abstract

The thermodynamics of the atropisomerisation of torsion angle restricted, axial chiral biphenyl-based push-pull cyclophanes were studied. Using 1H NMR coalescence measurements the rotation barrier around the central C–C bond was determined to be 50 kJ mol−1 for the propyl-bridged biphenyl derivative 1b, displaying only a negligible solvent dependence. By protonation of the piperidinyl nitrogen as electron donor, the free energy ΔG‡(T) of the rotation barrier increased, indicating that the tendency of the push-pull system to planarise may be considered as a driving force for the atropisomerisation. For the more restricted butyl-bridged cyclophane 1c a rotation barrier of ΔG‡(T) = 90 kJ mol−1 was measured using dynamic chromatography. The difference in the free energy of rotation around the central C–C bond probably reflects the crowdedness of the transition states.
Faculties and Departments:05 Faculty of Science > Departement Chemie > Chemie > Molecular Devices and Materials (Mayor)
UniBasel Contributors:Mayor, Marcel and Rotzler, Jürgen and Gsellinger, Heiko and Neuburger, Markus and Häussinger, Daniel and Vonlanthen, David
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Royal Society of Chemistry
ISSN:1477-0520
e-ISSN:1477-0539
Note:Publication type according to Uni Basel Research Database: Journal article
Identification Number:
Last Modified:29 Mar 2017 14:44
Deposited On:14 Sep 2012 07:06

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