The Experts below are selected from a list of 43515 Experts worldwide ranked by ideXlab platform
Chad A. Mirkin - One of the best experts on this subject based on the ideXlab platform.
-
reversible and selective encapsulation of dextromethorphan and β estradiol using an asymmetric molecular capsule assembled via the Weak Link approach
Journal of the American Chemical Society, 2017Co-Authors: Jose Mendezarroyo, Andrea I Daquino, Alyssa B Chinen, Yashin D Manraj, Chad A. MirkinAbstract:An allosterically regulated, asymmetric receptor featuring a binding cavity large enough to accommodate three-dimensional pharmaceutical guest molecules as opposed to planar, rigid aromatics, was synthesized via the Weak-Link Approach. This architecture is capable of switching between an expanded, flexible “open” configuration and a collapsed, rigid “closed” one. The structure of the molecular receptor can be completely modulated in situ through the use of simple ionic effectors, which reversibly control the coordination state of the Pt(II) metal hinges to open and close the molecular receptor. The substantial change in binding cavity size and electrostatic charge between the two configurations is used to explore the capture and release of two guest molecules, dextromethorphan and β-estradiol, which are widely found as pollutants in groundwater.
-
modulation of electronics and thermal stabilities of photochromic phosphino aminoazobenzene derivatives in Weak Link approach coordination complexes
Journal of the American Chemical Society, 2013Co-Authors: Jung Su Park, Jose Mendezarroyo, Charlotte L Stern, Alejo M Lifschitz, Ryan M Young, Michael R Wasielewski, Chad A. MirkinAbstract:A series of d(8) transition-metal (Pt(II) and Pd(II)) coordination complexes incorporating phosphine-functionalized aminoazobenzene derivatives as hemilabile phosphino-amine (P,N) ligands were synthesized and studied as model Weak-Link approach (WLA) photoresponsive constructs. The optical and photochemical properties of these complexes were found to be highly influenced by various tunable parameters in WLA systems, which include type of metal, coordination mode, type of ancillary ligand, solvent, and outer-sphere counteranions. In dichloromethane, reversible chelation and partial displacement of the P,N coordinating moieties allow for toggling between aminoazobenzene- or pseudostilbene- and azobenzene-type derivatives. The reversible switching between electronic states of azobenzene can be controlled through either addition or extraction of chloride counterions and is readily visualized in the separation between π-π* and n-π* bands in the complexes' electronic spectra. In acetonitrile solution, the WLA variables inherent to semiopen complexes have a significant impact on the half-lives of the corresponding cis isomers, allowing one to tune their half-lives from 20 to 21000 s, while maintaining photoisomerization behaviors with visible light. Therefore, one can significantly increase the thermal stability of a cis-aminoazobenzene derivative to the extent that single crystals for X-ray diffraction analysis can be grown for the first time, uncovering an unprecedented edge-to-face arrangement of the phenyl rings in the cis isomer. Overall, the azobenzene-functionalized model complexes shed light on the design parameters relevant for photocontrolled WLA molecular switches, as well as offer new ways of tuning the properties of azobenzene-based, photoresponsive materials.
-
general strategy for the synthesis of rigid Weak Link approach platinum ii complexes tweezers triple layer complexes and macrocycles
Inorganic Chemistry, 2013Co-Authors: Robert D Kennedy, Charles W Machan, Michael C Mcguirk, Mari S Rosen, Charlotte L Stern, Amy A Sarjeant, Chad A. MirkinAbstract:Air-stable, heteroligated platinum(II) Weak-Link approach (WLA) tweezer and triple-layer complexes that possess P,X–Aryl hemilabile ligands (P^ = Ph2PCH2CH2–, X = chalcoethers or amines) have been synthesized via the halide-induced ligand rearrangement (HILR) reaction, using a one-pot, partial chloride-abstraction method. The approach is general and works with a variety of phosphine-based hemilabile ligands; when a P,S–Ph ligand is used as the relatively strongly chelating ligand, heteroligated complexes are formed cleanly when an ether- (P,O–Ph), amine- (P,N–Ph2), or fluorinated thioether-based (P,S–C6F4H) hemilabile ligand is used as the Weakly chelating counterpart. The HILR reaction has also been used to synthesize bisplatinum(II) macrocycles free of oligomeric material without having to resort to the high-dilution conditions typical for macrocycle synthesis. This approach is complementary to the traditional WLA to the synthesis of macrocyclic complexes which typically proceeds via fully closed, chlor...
-
Modulation of Electronics and Thermal Stabilities of Photochromic Phosphino–Aminoazobenzene Derivatives in Weak-Link Approach Coordination Complexes
2013Co-Authors: Jung Su Park, Charlotte L Stern, Alejo M Lifschitz, Ryan M Young, Michael R Wasielewski, Jose Mendez-arroyo, Chad A. MirkinAbstract:A series of d8 transition-metal (Pt(II) and Pd(II)) coordination complexes incorporating phosphine-functionalized aminoazobenzene derivatives as hemilabile phosphino–amine (P,N) ligands were synthesized and studied as model Weak-Link approach (WLA) photoresponsive constructs. The optical and photochemical properties of these complexes were found to be highly influenced by various tunable parameters in WLA systems, which include type of metal, coordination mode, type of ancillary ligand, solvent, and outer-sphere counteranions. In dichloromethane, reversible chelation and partial displacement of the P,N coordinating moieties allow for toggling between aminoazobenzene- or pseudostilbene- and azobenzene-type derivatives. The reversible switching between electronic states of azobenzene can be controlled through either addition or extraction of chloride counterions and is readily visualized in the separation between π–π* and n−π* bands in the complexes’ electronic spectra. In acetonitrile solution, the WLA variables inherent to semiopen complexes have a significant impact on the half-lives of the corresponding cis isomers, allowing one to tune their half-lives from 20 to 21000 s, while maintaining photoisomerization behaviors with visible light. Therefore, one can significantly increase the thermal stability of a cis-aminoazobenzene derivative to the extent that single crystals for X-ray diffraction analysis can be grown for the first time, uncovering an unprecedented edge-to-face arrangement of the phenyl rings in the cis isomer. Overall, the azobenzene-functionalized model complexes shed light on the design parameters relevant for photocontrolled WLA molecular switches, as well as offer new ways of tuning the properties of azobenzene-based, photoresponsive materials
-
allosteric regulation of phosphate diester transesterification based upon a dinuclear zinc catalyst assembled via the Weak Link approach
Journal of the American Chemical Society, 2007Co-Authors: Hyo Jae Yoon, Jungseok Heo, Chad A. MirkinAbstract:The design and synthesis of a novel supramolecular allosteric catalyst, assembled via the Weak-Link approach, is presented. The catalyst shows completely reversible allosteric regulation for the catalytic cleavage of 2-(hydroxypropyl)-p-nitrophenyl phosphate (HPNP), which is an RNA model substrate. The system works under pseudo-aqueous conditions and can be turned completely off due to a bridging acetate ligand in the deactivated state, which inhibits the analogous intermolecular catalytic process.
G K Campbell - One of the best experts on this subject based on the ideXlab platform.
-
driving phase slips in a superfluid atom circuit with a rotating Weak Link
Physical Review Letters, 2013Co-Authors: Kevin Wright, R B Blakestad, C J Lobb, William D Phillips, G K CampbellAbstract:We have observed well-defined phase slips between quantized persistent current states around a toroidal atomic (23Na) Bose-Einstein condensate. These phase slips are induced by a Weak Link (a localized region of reduced superfluid density) rotated slowly around the ring. This is analogous to the behavior of a superconducting loop with a Weak Link in the presence of an external magnetic field. When the Weak Link is rotated more rapidly, well-defined phase slips no longer occur, and vortices enter into the bulk of the condensate. A noteworthy feature of this system is the ability to dynamically vary the current-phase relation of the Weak Link, a feature which is difficult to implement in superconducting or superfluid helium circuits.
-
superflow in a toroidal bose einstein condensate an atom circuit with a tunable Weak Link
Physical Review Letters, 2011Co-Authors: Anand Ramanathan, Kevin Wright, C J Lobb, William D Phillips, S R Muniz, Martin Zelan, W T Hill, Kristian Helmerson, G K CampbellAbstract:We have created a long-lived ({approx_equal}40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable Weak Link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local flow velocity at the barrier exceeds a critical velocity. The measured critical velocity is consistent with dissipation due to the creation of vortex-antivortex pairs. This system is the first realization of an elementary closed-loop atom circuit.
-
superflow in a toroidal bose einstein condensate an atom circuit with a tunable Weak Link
Physical Review Letters, 2011Co-Authors: Anand Ramanathan, Kevin Wright, C J Lobb, William D Phillips, S R Muniz, Martin Zelan, W T Hill, Kristian Helmerson, G K CampbellAbstract:We have created a long-lived ($\ensuremath{\approx}40\text{ }\text{ }\mathrm{s}$) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable Weak Link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local flow velocity at the barrier exceeds a critical velocity. The measured critical velocity is consistent with dissipation due to the creation of vortex-antivortex pairs. This system is the first realization of an elementary closed-loop atom circuit.
D Abukay - One of the best experts on this subject based on the ideXlab platform.
-
investigation of the variation in Weak Link profile of yba2cu3 xagxo7 δ superconductors by ag doping concentration
Solid State Communications, 2004Co-Authors: Mustafa Tepe, H Kocoglu, I Avci, D AbukayAbstract:Abstract The effect of Ag doping concentration on the microstructure, transport properties and Weak-Link profile of YBa 2 Cu 3− x Ag x O 7− δ bulk superconducting compound was investigated through resistance–temperature ( R – T ), ac magnetic susceptibility ( χ − T ), scanning electron microscope (SEM), X-ray diffraction (XRD) and the critical current density ( J c ) versus applied magnetic field ( J c − B ) measurements. We used the additive method with cationic ratio of x =0.1−0.4 for the YBCO-Ag system. The change in the silver doping concentration slightly affected the transition temperatures ( T c,zero ), whereas, the critical current densities ( J c ) of the samples and their magnetic field ( B ) dependencies were noticeably affected. The improvement on the microstructural properties of YBCO bulk superconductors was observed in SEM analysis, the J c values increased and their magnetic field dependencies decreased with the increasing of Ag concentration up to x =0.2. As well as the current transport properties. Ag doping up to a certain amount produces texturing that gives rise to a modification in the Weak-Link profile resulting in an enhanced strength of flux pinning which causes an increase in the current carrying capacity.
-
investigation of the variation in Weak Link profile of yba2cu3 xagxo7 δ superconductors by ag doping concentration
Solid State Communications, 2004Co-Authors: Mustafa Tepe, H Kocoglu, I Avci, D AbukayAbstract:Abstract The effect of Ag doping concentration on the microstructure, transport properties and Weak-Link profile of YBa 2 Cu 3− x Ag x O 7− δ bulk superconducting compound was investigated through resistance–temperature ( R – T ), ac magnetic susceptibility ( χ − T ), scanning electron microscope (SEM), X-ray diffraction (XRD) and the critical current density ( J c ) versus applied magnetic field ( J c − B ) measurements. We used the additive method with cationic ratio of x =0.1−0.4 for the YBCO-Ag system. The change in the silver doping concentration slightly affected the transition temperatures ( T c,zero ), whereas, the critical current densities ( J c ) of the samples and their magnetic field ( B ) dependencies were noticeably affected. The improvement on the microstructural properties of YBCO bulk superconductors was observed in SEM analysis, the J c values increased and their magnetic field dependencies decreased with the increasing of Ag concentration up to x =0.2. As well as the current transport properties. Ag doping up to a certain amount produces texturing that gives rise to a modification in the Weak-Link profile resulting in an enhanced strength of flux pinning which causes an increase in the current carrying capacity.
Kevin Wright - One of the best experts on this subject based on the ideXlab platform.
-
driving phase slips in a superfluid atom circuit with a rotating Weak Link
Physical Review Letters, 2013Co-Authors: Kevin Wright, R B Blakestad, C J Lobb, William D Phillips, G K CampbellAbstract:We have observed well-defined phase slips between quantized persistent current states around a toroidal atomic (23Na) Bose-Einstein condensate. These phase slips are induced by a Weak Link (a localized region of reduced superfluid density) rotated slowly around the ring. This is analogous to the behavior of a superconducting loop with a Weak Link in the presence of an external magnetic field. When the Weak Link is rotated more rapidly, well-defined phase slips no longer occur, and vortices enter into the bulk of the condensate. A noteworthy feature of this system is the ability to dynamically vary the current-phase relation of the Weak Link, a feature which is difficult to implement in superconducting or superfluid helium circuits.
-
superflow in a toroidal bose einstein condensate an atom circuit with a tunable Weak Link
Physical Review Letters, 2011Co-Authors: Anand Ramanathan, Kevin Wright, C J Lobb, William D Phillips, S R Muniz, Martin Zelan, W T Hill, Kristian Helmerson, G K CampbellAbstract:We have created a long-lived ({approx_equal}40 s) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable Weak Link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local flow velocity at the barrier exceeds a critical velocity. The measured critical velocity is consistent with dissipation due to the creation of vortex-antivortex pairs. This system is the first realization of an elementary closed-loop atom circuit.
-
superflow in a toroidal bose einstein condensate an atom circuit with a tunable Weak Link
Physical Review Letters, 2011Co-Authors: Anand Ramanathan, Kevin Wright, C J Lobb, William D Phillips, S R Muniz, Martin Zelan, W T Hill, Kristian Helmerson, G K CampbellAbstract:We have created a long-lived ($\ensuremath{\approx}40\text{ }\text{ }\mathrm{s}$) persistent current in a toroidal Bose-Einstein condensate held in an all-optical trap. A repulsive optical barrier across one side of the torus creates a tunable Weak Link in the condensate circuit, which can affect the current around the loop. Superflow stops abruptly at a barrier strength such that the local flow velocity at the barrier exceeds a critical velocity. The measured critical velocity is consistent with dissipation due to the creation of vortex-antivortex pairs. This system is the first realization of an elementary closed-loop atom circuit.
I Avci - One of the best experts on this subject based on the ideXlab platform.
-
investigation of the variation in Weak Link profile of yba2cu3 xagxo7 δ superconductors by ag doping concentration
Solid State Communications, 2004Co-Authors: Mustafa Tepe, H Kocoglu, I Avci, D AbukayAbstract:Abstract The effect of Ag doping concentration on the microstructure, transport properties and Weak-Link profile of YBa 2 Cu 3− x Ag x O 7− δ bulk superconducting compound was investigated through resistance–temperature ( R – T ), ac magnetic susceptibility ( χ − T ), scanning electron microscope (SEM), X-ray diffraction (XRD) and the critical current density ( J c ) versus applied magnetic field ( J c − B ) measurements. We used the additive method with cationic ratio of x =0.1−0.4 for the YBCO-Ag system. The change in the silver doping concentration slightly affected the transition temperatures ( T c,zero ), whereas, the critical current densities ( J c ) of the samples and their magnetic field ( B ) dependencies were noticeably affected. The improvement on the microstructural properties of YBCO bulk superconductors was observed in SEM analysis, the J c values increased and their magnetic field dependencies decreased with the increasing of Ag concentration up to x =0.2. As well as the current transport properties. Ag doping up to a certain amount produces texturing that gives rise to a modification in the Weak-Link profile resulting in an enhanced strength of flux pinning which causes an increase in the current carrying capacity.
-
investigation of the variation in Weak Link profile of yba2cu3 xagxo7 δ superconductors by ag doping concentration
Solid State Communications, 2004Co-Authors: Mustafa Tepe, H Kocoglu, I Avci, D AbukayAbstract:Abstract The effect of Ag doping concentration on the microstructure, transport properties and Weak-Link profile of YBa 2 Cu 3− x Ag x O 7− δ bulk superconducting compound was investigated through resistance–temperature ( R – T ), ac magnetic susceptibility ( χ − T ), scanning electron microscope (SEM), X-ray diffraction (XRD) and the critical current density ( J c ) versus applied magnetic field ( J c − B ) measurements. We used the additive method with cationic ratio of x =0.1−0.4 for the YBCO-Ag system. The change in the silver doping concentration slightly affected the transition temperatures ( T c,zero ), whereas, the critical current densities ( J c ) of the samples and their magnetic field ( B ) dependencies were noticeably affected. The improvement on the microstructural properties of YBCO bulk superconductors was observed in SEM analysis, the J c values increased and their magnetic field dependencies decreased with the increasing of Ag concentration up to x =0.2. As well as the current transport properties. Ag doping up to a certain amount produces texturing that gives rise to a modification in the Weak-Link profile resulting in an enhanced strength of flux pinning which causes an increase in the current carrying capacity.
