Paramagnetic Molecular Grippers: The Elements of Six-State Redox Switches.
The development of semiquinone-based resorcin[4]arene cavitands expands the toolbox of switchable molecular grippers by introducing the first paramagnetic representatives. The semiquinone (SQ) states were generated electrochemically, chemically, and photochemically. We analyzed their electronic, conformational, and binding properties by cyclic voltammetry, ultraviolet/visible (UV/vis) spectroelectrochemistry, electron paramagnetic resonance (EPR) and transient absorption spectroscopy, in conjunction with density functional theory (DFT) calculations. The utility of UV/vis spectroelectrochemistry and EPR spectroscopy in evaluating the conformational features of resorcin[4]arene cavitands is demonstrated. Guest binding properties were found to be enhanced in the SQ state as compared to the quinone (Q) or the hydroquinone (HQ) states of the cavitands. Thus, these paramagnetic SQ intermediates open the way to six-state redox switches provided by two conformations (open and closed) in three redox states (Q, SQ, and HQ) possessing distinct binding ability. The switchable magnetic properties of these molecular grippers and their responsiveness to electrical stimuli has the potential for development of efficient molecular devices.
Laboratory of Organic Chemistry, ETH Zurich , Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
Jovana
J
Milić
Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.|Institute of Physical Chemistry and Chemical Physics, Slovak University of Technology in Bratislava, Faculty of Chemical and Food Technology , Radlinského 9, 81237 Bratislava, Slovak Republic.
Michal
M
Zalibera
Laboratory of Organic Chemistry, ETH Zurich , Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
Igor
I
Pochorovski
Laboratory of Organic Chemistry, ETH Zurich , Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
Nils
N
Trapp
Department of Chemistry, University of Basel , St. Johanns-Ring 19, 4056 Basel, Switzerland.
Julia
J
Nomrowski
Institute of Physical and Theoretical Chemistry, NAWI Graz, Graz University of Technology , Stremayrgasse 9/Z2, 8010 Graz, Austria.
Dmytro
D
Neshchadin
Université de Strasbourg, Laboratoire d'Électrochimie et Chimie Physique du Corps Solide, Institut de Chimie de Strasbourg, 4 rue Blaise Pascal, CS 90032, 67081 Strasbourg, France.
Laurent
L
Ruhlmann
Université de Strasbourg, Laboratoire d'Électrochimie et Chimie Physique du Corps Solide, Institut de Chimie de Strasbourg, 4 rue Blaise Pascal, CS 90032, 67081 Strasbourg, France.
Corinne
C
Boudon
Department of Chemistry, University of Basel , St. Johanns-Ring 19, 4056 Basel, Switzerland.
Oliver S
OS
Wenger
Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Anton
A
Savitsky
Max Planck Institute for Chemical Energy Conversion , Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany.
Wolfgang
W
Lubitz
Institute of Physical and Theoretical Chemistry, NAWI Graz, Graz University of Technology , Stremayrgasse 9/Z2, 8010 Graz, Austria.
Georg
G
Gescheidt
Laboratory of Organic Chemistry, ETH Zurich , Vladimir-Prelog-Weg 3, 8093 Zurich, Switzerland.
François
F
Diederich