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From Molecules to Materials: Engineering New Ionic Liquid Crystals Through Halogen Bonding
Published on: March 24, 2018
Intramolecular halogen stabilization of silylium ions directs gearing dynamics
Paola Romanato1, Simon Duttwyler, Anthony Linden
1Organic Chemistry Institute, University of Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland.
Abstract:
2,6-Bis(2,6-difluorophenyl)phenyldimethylsilanium ion (1a) adopts a ground-state C(2) trigonal-bipyramidal geometry in which fluorines from opposing 2,6-difluorophenyl groups coordinate to the apical positions of the pentavalent silyl cation. Exchange of fluorine at silicon occurs by a disrotatory gearing mechanism wherein one fluorine remains coordinated to silicon throughout the circuit. The "cogwheel" transition state is C(s)-symmetric, with one ring having a dihedral angle of 0 degrees and the other a dihedral angle of 90 degrees. This correlated dynamic process is a function of the coordinating halogen. The chloro derivative (1b) adopts a similar ground-state geometry, but exchange of chlorine at silicon follows a conrotatory process.
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