The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Bruce P Branchaud - One of the best experts on this subject based on the ideXlab platform.
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180° Unidirectional Bond Rotation in a Biaryl Lactone Artificial Molecular Motor Prototype
Organic Letters, 2006Co-Authors: Bart J. Dahl And, Bruce P BranchaudAbstract:A bifunctional biaryl lactone has been synthesized that should be capable of iterative unidirectional aryl−aryl Bond Rotation via: (1) a diastereoselective lactone ring opening, (S)-1 to (P,S)-2 or (M,S)-2; (2) a chemoselective lactonization, (P,S)-2 or (M,S)-2 to (S)-3; and (3) a chemoselective hydrolysis, (S)-3 to (S)-1. Preliminary results of a racemic sample have indicated unidirectional 180° Rotation with very high directional selectivity per individual artificial molecular motor molecule through the first two steps of this sequence.
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180 unidirectional Bond Rotation in a biaryl lactone artificial molecular motor prototype
Organic Letters, 2006Co-Authors: Bruce P BranchaudAbstract:A bifunctional biaryl lactone has been synthesized that should be capable of iterative unidirectional aryl−aryl Bond Rotation via: (1) a diastereoselective lactone ring opening, (S)-1 to (P,S)-2 or (M,S)-2; (2) a chemoselective lactonization, (P,S)-2 or (M,S)-2 to (S)-3; and (3) a chemoselective hydrolysis, (S)-3 to (S)-1. Preliminary results of a racemic sample have indicated unidirectional 180° Rotation with very high directional selectivity per individual artificial molecular motor molecule through the first two steps of this sequence.
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net directed 180 aryl aryl Bond Rotation in a prototypical achiral biaryl lactone synthetic molecular motor
Tetrahedron Letters, 2005Co-Authors: Bart J Dahl, Bruce P BranchaudAbstract:Abstract Net directed 180° Bond Rotation was achieved through diastereoselective ring-opening reactions in an achiral biaryl lactone using a chiral nucleophile followed by re-lactonization. The efficiency of the directed Bond Rotation has been determined by HPLC–MS to be 50% and 20% with two different chiral nucleophiles. These results demonstrate the potential for a prototype of a chemically driven synthetic molecular motor which has the advantages of both simplicity and flexibility in operation and is the first example of the use of a chiral auxiliary to induce transient axial chirality resulting in net directed Bond Rotation.
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Net directed 180° aryl-aryl Bond Rotation in a prototypical achiral biaryl lactone synthetic molecular motor
Tetrahedron Letters, 2005Co-Authors: Bart J Dahl, Bruce P BranchaudAbstract:Abstract Net directed 180° Bond Rotation was achieved through diastereoselective ring-opening reactions in an achiral biaryl lactone using a chiral nucleophile followed by re-lactonization. The efficiency of the directed Bond Rotation has been determined by HPLC–MS to be 50% and 20% with two different chiral nucleophiles. These results demonstrate the potential for a prototype of a chemically driven synthetic molecular motor which has the advantages of both simplicity and flexibility in operation and is the first example of the use of a chiral auxiliary to induce transient axial chirality resulting in net directed Bond Rotation.
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synthesis and characterization of a functionalized chiral biaryl capable of exhibiting unidirectional Bond Rotation
Tetrahedron Letters, 2004Co-Authors: Bart J Dahl, Bruce P BranchaudAbstract:A class of chiral biaryl molecules that have been designed to undergo unidirectional Rotation about the aryl–aryl Bond may show promise for future application in the area of synthetic molecular motors. These asymmetric molecules should be capable of channeling chemical energy into repeated 360° Rotation in one direction. Herein we report the synthesis and characterization of one such biaryl molecule (1).
Jeanmarie Lehn - One of the best experts on this subject based on the ideXlab platform.
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internal c c Bond Rotation in photoisomers of α bisimines a light responsive two step molecular speed regulator based on double imine photoswitching
European Journal of Organic Chemistry, 2016Co-Authors: Lutz Greb, Andreas Eichhofer, Jeanmarie LehnAbstract:Benzil-based α-bisimines are implemented as photoswitches for the construction of a speed-regulating molecular device, in which, by application of light, three different states may be addressed, showing distinct frequencies of internal C–C Bond Rotation, spanning 12 orders of magnitude. Bond Rotation barriers were determined experimentally and elucidated by DFT-methods.
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Internal C–C Bond Rotation in Photoisomers of α-Bisimines: a Light-Responsive Two-Step Molecular Speed Regulator Based on Double Imine Photoswitching
European Journal of Organic Chemistry, 2016Co-Authors: Lutz Greb, Andreas Eichhofer, Jeanmarie LehnAbstract:Benzil-based α-bisimines are implemented as photoswitches for the construction of a speed-regulating molecular device, in which, by application of light, three different states may be addressed, showing distinct frequencies of internal C–C Bond Rotation, spanning 12 orders of magnitude. Bond Rotation barriers were determined experimentally and elucidated by DFT-methods.
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synthetic molecular motors thermal n inversion and directional photoinduced cn Bond Rotation of camphorquinone imines
Angewandte Chemie, 2015Co-Authors: Lutz Greb, Andreas Eichhofer, Jeanmarie LehnAbstract:The thermal and photochemical E/Z isomerization of camphorquinone-derived imines was studied by a combination of kinetic, structural, and computational methods. The thermal isomerization proceeds by linear N inversion, whereas the photoinduced process occurs through C=N Bond Rotation with preferred directionality as a result of diastereoisomerism. Thereby, these imines are arguably the simplest example of synthetic molecular motors. The generality of the orthogonal trajectories of the thermal and photochemical pathways allows for the postulation that every suitable chiral imine qualifies, in principle, as a molecular motor driven by light or heat.
Yufen Zhao - One of the best experts on this subject based on the ideXlab platform.
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investigation of the c n Bond Rotation of spirophosphorane carbamates by dynamic nmr and dft calculation
Tetrahedron, 2015Co-Authors: Pei Zhao, Yanyan Wang, Miaomiao Peng, Yufen ZhaoAbstract:Abstract Spirophosphorane carbamates are a new type of pentacoordinate phosphorus compounds. In order to explore internal Rotation, the dynamic 1H NMR, 31P NMR and molecular theory calculations were employed to investigate the Rotation barriers of the N–C( O) Bond of symmetrical and asymmetrical spirophosphorane carbamates. The Gibbs free activation, ΔG≠, was calculated by Eyring equation. The results showed that the Rotation barriers of spirophosphorane carbamates were about 16–18 kcal/mol, and the Rotation isomers coexisted at room temperature. Moreover, it was found that the benzyl group attached to amide nitrogen increased the C–N Bond Rotation barriers of spirophosphorane carbamates. Furthermore, the preferred conformation of spirophosphorane carbamates was presumed by density functional theory (DFT), and the conformation of solid state were also confirmed by X-ray diffraction analysis.
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Investigation of the C–N Bond Rotation of spirophosphorane carbamates by dynamic NMR and DFT calculation
Tetrahedron, 2015Co-Authors: Pei Zhao, Yanyan Wang, Miaomiao Peng, Yufen ZhaoAbstract:Abstract Spirophosphorane carbamates are a new type of pentacoordinate phosphorus compounds. In order to explore internal Rotation, the dynamic 1H NMR, 31P NMR and molecular theory calculations were employed to investigate the Rotation barriers of the N–C( O) Bond of symmetrical and asymmetrical spirophosphorane carbamates. The Gibbs free activation, ΔG≠, was calculated by Eyring equation. The results showed that the Rotation barriers of spirophosphorane carbamates were about 16–18 kcal/mol, and the Rotation isomers coexisted at room temperature. Moreover, it was found that the benzyl group attached to amide nitrogen increased the C–N Bond Rotation barriers of spirophosphorane carbamates. Furthermore, the preferred conformation of spirophosphorane carbamates was presumed by density functional theory (DFT), and the conformation of solid state were also confirmed by X-ray diffraction analysis.
Lutz Greb - One of the best experts on this subject based on the ideXlab platform.
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internal c c Bond Rotation in photoisomers of α bisimines a light responsive two step molecular speed regulator based on double imine photoswitching
European Journal of Organic Chemistry, 2016Co-Authors: Lutz Greb, Andreas Eichhofer, Jeanmarie LehnAbstract:Benzil-based α-bisimines are implemented as photoswitches for the construction of a speed-regulating molecular device, in which, by application of light, three different states may be addressed, showing distinct frequencies of internal C–C Bond Rotation, spanning 12 orders of magnitude. Bond Rotation barriers were determined experimentally and elucidated by DFT-methods.
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Internal C–C Bond Rotation in Photoisomers of α-Bisimines: a Light-Responsive Two-Step Molecular Speed Regulator Based on Double Imine Photoswitching
European Journal of Organic Chemistry, 2016Co-Authors: Lutz Greb, Andreas Eichhofer, Jeanmarie LehnAbstract:Benzil-based α-bisimines are implemented as photoswitches for the construction of a speed-regulating molecular device, in which, by application of light, three different states may be addressed, showing distinct frequencies of internal C–C Bond Rotation, spanning 12 orders of magnitude. Bond Rotation barriers were determined experimentally and elucidated by DFT-methods.
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synthetic molecular motors thermal n inversion and directional photoinduced cn Bond Rotation of camphorquinone imines
Angewandte Chemie, 2015Co-Authors: Lutz Greb, Andreas Eichhofer, Jeanmarie LehnAbstract:The thermal and photochemical E/Z isomerization of camphorquinone-derived imines was studied by a combination of kinetic, structural, and computational methods. The thermal isomerization proceeds by linear N inversion, whereas the photoinduced process occurs through C=N Bond Rotation with preferred directionality as a result of diastereoisomerism. Thereby, these imines are arguably the simplest example of synthetic molecular motors. The generality of the orthogonal trajectories of the thermal and photochemical pathways allows for the postulation that every suitable chiral imine qualifies, in principle, as a molecular motor driven by light or heat.
Klaas J Hellingwerf - One of the best experts on this subject based on the ideXlab platform.
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on the involvement of single Bond Rotation in the primary photochemistry of photoactive yellow protein
Biophysical Journal, 2011Co-Authors: Andreas D Stahl, Marijke Hospes, Kushagra Singhal, Ivo H M Van Stokkum, Rienk Van Grondelle, Marie Louise Groot, Klaas J HellingwerfAbstract:Prior experimental observations, as well as theoretical considerations, have led to the proposal that C4-C7 single-Bond Rotation may play an important role in the primary photochemistry of photoactive yellow protein (PYP). We therefore synthesized an analog of this protein's 4-hydroxy-cinnamic acid chromophore, (5-hydroxy indan-(1E)-ylidene)acetic acid, in which Rotation across the C4-C7 single Bond has been locked with an ethane bridge, and we reconstituted the apo form of the wild-type protein and its R52A derivative with this chromophore analog. In PYP reconstituted with the Rotation-locked chromophore, 1), absorption spectra of ground and intermediate states are slightly blue-shifted; 2), the quantum yield of photochemistry is ∼60% reduced; 3), the excited-state dynamics of the chromophore are accelerated; and 4), dynamics of the thermal recovery reaction of the protein are accelerated. A significant finding was that the yield of the transient ground-state intermediate in the early phase of the photocycle was considerably higher in the Rotation-locked samples than in the corresponding samples reconstituted with p-coumaric acid. In contrast to theoretical predictions, the initial photocycle dynamics of PYP were observed to be not affected by the charge of the amino acid residue at position 52, which was varied by 1), varying the pH of the sample between 5 and 10; and 2), site-directed mutagenesis to construct R52A. These results imply that C4-C7 single-Bond Rotation in PYP is not an alternative to C7=C8 double-Bond Rotation, in case the nearby positive charge of R52 is absent, but rather facilitates, presumably with a compensatory movement, the physiological Z/E isomerization of the blue-light-absorbing chromophore.