31 results on '"David S. Laitar"'
Search Results
2. Novel Strategy for Photopatterning Emissive Polymer Brushes for Organic Light Emitting Diode Applications
- Author
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Zachariah A. Page, Benjaporn Narupai, Christian W. Pester, Raghida Bou Zerdan, Anatoliy Sokolov, David S. Laitar, Sukrit Mukhopadhyay, Scott Sprague, Alaina J. McGrath, John W. Kramer, Peter Trefonas, and Craig J. Hawker
- Subjects
Chemistry ,QD1-999 - Published
- 2017
- Full Text
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3. Silicone‐based polymer blends: Enhancing properties through compatibilization
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Michael Czuczola, Morgan W. Bates, David S. Laitar, Jodi M. Mecca, Zhishuai Geng, Craig J. Hawker, Thomas D. Bekemeier, Steven Swier, Jae Man Shin, Christopher M. Bates, Allison Abdilla, David J. Goldfeld, Colton D'Ambra, and Souvagya Biswas
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chemistry.chemical_classification ,Materials science ,Polymers and Plastics ,Nanotechnology ,02 engineering and technology ,Polymer ,Compatibilization ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Soft materials ,0104 chemical sciences ,chemistry.chemical_compound ,Silicone ,chemistry ,Materials Chemistry ,Polymer blend ,Physical and Theoretical Chemistry ,0210 nano-technology - Abstract
Polymer blending is a cost-effective way to control the properties of soft materials, but the propensity for blends to macrophase separate motivates the development of efficient compatibilization strategies. Across this broad area, compatibilization is particularly important for polysiloxanes, which exhibit strong repulsive interactions with most organic polymers. This review analyzes state-of-the-art polysiloxane compatibilization strategies for silicone–organic polymer blends. Emphasis is placed on chemical innovation in the design of compatibilization agents that may expedite the commercialization of new silicone–organic materials. We anticipate that hybrid silicone blends will continue to play an important role in fundamental and applied materials science across industry and academia.
- Published
- 2021
4. Homoconjugated Acids as Low Cyclosiloxane-Producing Silanol Polycondensation Catalysts
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Matthew E. Belowich, Thomas H. Peterson, Edward Bellinger, Karin Syverud, Tobias Sidle, David S Laitar, and Roberts John
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Chemistry ,Silanol ,chemistry.chemical_compound ,Condensation polymer ,chemistry ,General Chemical Engineering ,Organic chemistry ,General Chemistry ,Brønsted–Lowry acid–base theory ,QD1-999 ,Catalysis - Abstract
Polycondensation of α,ω-disilanols is a foundational technology for silicones producers. Commercially, this process is carried out with strong Brønsted acids and bases, which generates cyclosiloxane byproducts. Homoconjugated acids (a 2:1 complex of acid:base or a 1:1 complex of acid:salt), a seldom used class of silanol polycondensation catalysts, were evaluated for their ability to polymerize α,ω-disilanols while forming low levels of cyclosiloxane byproducts. Homoconjugated acid catalysts were highly active for silanol polycondensation, even when made from relatively mild acids such as acetic acid. Both the acid and base (or cation) component of the homoconjugated species was important for activity and avoiding cyclosiloxane byproduct formation. Stronger acids and bases were found to positively affect reactivity, and the p
- Published
- 2020
5. Efficient synthesis of branched poly(acrylic acid) derivatives via postpolymerization modification
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Raghida Bou Zerdan, Benjaporn Narupai, David S. Laitar, Yvonne J. Diaz, Antony K. Van Dyk, Biswas Souvagya, Zhishuai Geng, Craig J. Hawker, and Morgan W. Bates
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chemistry.chemical_classification ,Acrylate ,Polymers and Plastics ,Radical polymerization ,Chain transfer ,Pentafluorophenyl esters ,02 engineering and technology ,Tricarboxylic acid ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Polymer chemistry ,Materials Chemistry ,Side chain ,Trifluoroacetic acid ,Physical and Theoretical Chemistry ,0210 nano-technology ,Acrylic acid - Abstract
The utility of pentafluorophenyl esters for the selective introduction of functional units and branch points in well-defined poly(acrylic acid) (PAA) derivatives is demonstrated using a combination of controlled radical polymerization and postpolymerization modification. Reversible addition-fragmentation chain transfer enables the synthesis of well-defined copolymers-poly(pentafluorophenyl acrylate-co-tert-butyl acrylate)-with the active ester repeat units serving as attachment points for reaction with primary amines, specifically tris(2-(t-butoxycarbonyl)ethyl)methyl amine (Behera's amine). Deprotection using trifluoroacetic acid removes both the backbone and side chaint-butyl esters to give a series of branched PAA derivatives containing novel tricarboxylic acid side chains that are well suited to complexation and multidentate interactions. Surprisingly, the active ester homopolymer is shown to have the highest reactivity with Behera's amine when compared to copolymers with lower incorporation of pentafluorophenyl esters, suggesting an intriguing interplay of neighboring group effects and steric interactions. The ability to tune the efficiency of postpolymerization modification gives a library of PAA derivatives.
- Published
- 2020
6. Low‐Temperature, Rapid Copolymerization of Acrylic Acid and Sodium Acrylate in Water
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Tom H. Kalantar, Athina Anastasaki, Raghida Bou Zerdan, Johannes Willenbacher, In-Hwan Lee, Benjaporn Narupai, Alaina J. McGrath, Jing M. Ren, David S. Laitar, Craig J. Hawker, Morgan W. Bates, Stephanie M. Barbon, Antony K. Van Dyk, and Emre H. Discekici
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chemistry.chemical_classification ,Aqueous solution ,Polymers and Plastics ,Chemistry ,Organic Chemistry ,Dispersity ,Degenerative chain transfer ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,Polymerization ,Sodium iodide ,Materials Chemistry ,Copolymer ,Organic chemistry ,0210 nano-technology ,Alkyl ,Acrylic acid - Abstract
Regulating the aqueous polymerization of acrylic acid (AA) is a major opportunity for future materials design, requiring the development of scalable, industry‐oriented procedures that afford modest molar mass and dispersity control without long reaction times and environmentally demanding conditions. To address these challenges, this report presents the rapid copolymerization of aqueous mixtures of AA and sodium acrylate using an inexpensive and scalable protocol based on alkyl iodides/sodium iodide as mediators in water.
- Published
- 2019
7. Aqueous reverse iodine transfer polymerization of acrylic acid
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Antony K. Van Dyk, In-Hwan Lee, Jing M. Ren, Emre H. Discekici, David S. Laitar, Craig J. Hawker, Morgan W. Bates, Alaina J. McGrath, Tom H. Kalantar, and Javier Read de Alaniz
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Aqueous solution ,Polymers and Plastics ,Organic Chemistry ,chemistry.chemical_element ,02 engineering and technology ,Potassium persulfate ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Iodine ,01 natural sciences ,0104 chemical sciences ,chemistry.chemical_compound ,chemistry ,Polymerization ,Reagent ,Sodium iodide ,Materials Chemistry ,Radical initiator ,0210 nano-technology ,Nuclear chemistry ,Acrylic acid - Abstract
The utilization of sodium iodide, potassium persulfate, and a thermal radical initiator enables facile access to PAA via the direct reverse iodine transfer polymerization of acrylic acid. This polymerization proceeds rapidly in aqueous media using inexpensive and commercially available reagents.
- Published
- 2019
8. A Versatile and Efficient Strategy to Discrete Conjugated Oligomers
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Brenden McDearmon, Eisuke Goto, Jimmy Lawrence, Tomoya Higashihara, Paul G. Clark, Jing M. Ren, David S. Laitar, Craig J. Hawker, Yuto Ochiai, and Dong Sub Kim
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010405 organic chemistry ,Dispersity ,Sequence (biology) ,Nanotechnology ,General Chemistry ,Conjugated system ,010402 general chemistry ,01 natural sciences ,Biochemistry ,Combinatorial chemistry ,Catalysis ,0104 chemical sciences ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Monomer ,chemistry ,Polymerization ,Yield (chemistry) ,Electronic properties - Abstract
An efficient and scalable strategy to prepare libraries of discrete conjugated oligomers (Đ = 1.0) using the combination of controlled polymerization and automated flash chromatography is reported. From this two-step process, a series of discrete conjugated materials from dimers to tetradecamers could be isolated in high yield with excellent structural control. Facile and scalable access to monodisperse libraries of different conjugated oligomers opens pathways to designer mixtures with precise composition and monomer sequence, allowing exquisite control over their physical, optical, and electronic properties.
- Published
- 2017
9. Boron-based TADF emitters with improved OLED device efficiency roll-off and long lifetime
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Kenneth L. Kearns, Tomas D. Paine, David S. Laitar, Timothy S. De Vries, Jeong-Hwan Jeon, Sukrit Mukhopadhyay, Thomas P. Clark, Aaron A. Rachford, Timothy J. Gallagher, Hong-Yeop Na, Bruce M. Bell, Yuming Lai, and Mcintire Travis E
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Photoluminescence ,Materials science ,business.industry ,Process Chemistry and Technology ,General Chemical Engineering ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Acceptor ,0104 chemical sciences ,Delocalized electron ,chemistry ,Excited state ,OLED ,Optoelectronics ,Density functional theory ,Singlet state ,0210 nano-technology ,business ,Boron - Abstract
A class of four-coordinate boron complexes is reported that contain both electron-rich and electron-poor functional groups. Judicious selection of donor and acceptor moieties with the use of a boron atom as a separating node yields charge transfer complexes capable of thermally activated delayed fluorescence (TADF). Complexes were prepared by a modular method providing access to a wide range of emission colors. The singlet (S1) and triplet (T1) energies are independently tuned to achieve a small S1-T1 gap. Raising and lowering of S1 and T1 states can be predicted using cyclic voltammetry, NTO analysis, and spin density distribution as determined using Density Functional Theory; separation of the hole and electron wavefunction for S1 excitation and delocalization of spin density distribution in the T1 state can help in achieving negligible S1-T1 gap. Although photoluminescent quantum yields of the boron complexes in a host matrix are less than 65%, OLED device external quantum efficiencies of up to 8.1% have been achieved at a luminance of 1000 cd/m2. Selection of a boron emitter with a gap of less than 0.01 eV between the singlet and triplet excited state enables the fabrication of a device with low efficiency roll-off and long lifetime.
- Published
- 2017
10. Highly Photoluminescent Nonconjugated Polymers for Single-Layer Light Emitting Diodes
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Benjaporn Narupai, Alaina J. McGrath, Chien-Yang Chiu, Anatoliy N. Sokolov, Craig J. Hawker, Sukrit Mukhopadhyay, Raghida Bou Zerdan, Zachariah A. Page, Zachary M. Hudson, Bryan E. Barton, John W. Kramer, and David S. Laitar
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Materials science ,Photoluminescence ,chemistry.chemical_element ,02 engineering and technology ,010402 general chemistry ,Methacrylate ,01 natural sciences ,law.invention ,law ,OLED ,Iridium ,Electrical and Electronic Engineering ,chemistry.chemical_classification ,Dopant ,business.industry ,Polymer ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Optoelectronics ,0210 nano-technology ,business ,Phosphorescence ,Biotechnology ,Light-emitting diode - Abstract
The design, synthesis, and characterization of solution-processable polymers for organic light emitting diode (OLED) applications are presented. Theoretical calculations were employed to identify a carbazole-pyrimidine based building block as an optimized host material for the emissive layer of an idealized OLED stack. Efficient, free radical homopolymerization and copolymerization with a novel methacrylate-based heteroleptic iridium(III) complex leads to a library of nonconjugated polymers with pendant semiconductors. Optoelectronic characterization reveals impressive photoluminescence quantum yield (PLQY) values exceeding 80% and single-layer OLEDs show optimal performance for copolymers containing 6 mol % of iridium comonomer dopant.
- Published
- 2017
11. Dual-pathway chain-end modification of RAFT polymers using visible light and metal-free conditions
- Author
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Jia Niu, Craig J. Hawker, Javier Read de Alaniz, Paul G. Clark, In-Hwan Lee, David S. Laitar, Bernd Oschmann, Emre H. Discekici, Athina Anastasaki, David J. Lunn, Alaina J. McGrath, and Shelby L. Shankel
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chemistry.chemical_classification ,Hydrogen ,010405 organic chemistry ,Metals and Alloys ,chemistry.chemical_element ,Nanotechnology ,General Chemistry ,Polymer ,Raft ,010402 general chemistry ,Cleavage (embryo) ,01 natural sciences ,Combinatorial chemistry ,Article ,Catalysis ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry ,Chain (algebraic topology) ,Reagent ,Materials Chemistry ,Ceramics and Composites ,Thiol ,Visible spectrum - Abstract
We report a metal-free strategy for the chain-end modification of RAFT polymers utilizing visible light. By turning the light source on or off, the reaction pathway in one pot can be switched between either complete desulfurization (hydrogen chain-end) or simple cleavage (thiol chain-end), respectively. The versatility of this process is exemplified by application to a wide range of polymer backbones under mild, quantitative conditions using commercial reagents.
- Published
- 2017
12. Kinetic modeling of 1,2-dichloropropane (PDC) free-radical chlorination
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Max Markus Tirtowidjojo, Christina Zarth, Hangyao Wang, and David S. Laitar
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Allyl chloride ,Work (thermodynamics) ,Environmental Engineering ,Vapor pressure ,Chemistry ,General Chemical Engineering ,Ab initio ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Chemical kinetics ,chemistry.chemical_compound ,Computational chemistry ,Yield (chemistry) ,Elementary reaction ,Physical chemistry ,Chemical equilibrium ,0210 nano-technology ,Biotechnology - Abstract
Recent government mandates have lowered the permissible global warming potential (GWP) for refrigerants in mobile air conditioning substantially below that of the hydrofluorocarbon products that are used currently. Potential replacements, hydrofluoro-olefins (HFO), have a reduced impact on the ozone layer and lower GWP. Many desirable HFO compounds, such as HFO-1234yf, can be produced utilizing chlorocarbons as feedstocks such as the preferred 1,1,2,3-tetrachloropropene (TCPE). TCPE can be produced by several routes; however, producing TCPE from 1,2-dichloropropane (PDC) is potentially more desirable environmentally and economically since PDC is a byproduct of propylene oxide and allyl chloride production. One process option is to convert PDC to pentachloropropane (PCP) intermediates by chlorination, followed by dehydrochlorination of the PCPs to produce TCPE. In this work, we show that PCPs can be produced through the chlorination of PDC in a free-radical liquid phase reaction and have developed a kinetic model for PDC chlorination based on the relevant free radical elementary reactions. Thermodynamic properties including standard heats of formation, standard entropies of formation, and heat capacities for the radical and non-radical species were estimated by using ab initio and COSMOtherm calculations and validated against available experimental data. The reaction equilibrium constants were determined from the Gibb's free energies of the reactants and products. Phase equilibria were calculated by means of a consistent set of thermodynamic properties of the species. In addition, physical properties such as the vapor pressure of pure components involved in the reaction network were also estimated. Ab initio transition state calculations were employed to estimate the rate parameters including pre-exponential factors and activation energies for the relevant reactions. The activation energies of some key reactions were then adjusted to match experimental data. The resulting kinetic model provided a basis for process yield optimization and scale up. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1174–1191, 2016
- Published
- 2016
13. Direct Access to Functional (Meth)acrylate Copolymers through Transesterification with Lithium Alkoxides
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Will R. Gutekunst, Athina Anastasaki, Carolin Fleischmann, Craig J. Hawker, Paul G. Clark, Alaina J. McGrath, Phillip D. Hustad, and David S. Laitar
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Materials science ,Polymers and Plastics ,Polymers ,Radical polymerization ,Alkyne ,Ether ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Article ,Macromolecular and Materials Chemistry ,chemistry.chemical_compound ,Polymer chemistry ,Materials Chemistry ,Copolymer ,Organic chemistry ,functionalization of polymers ,Methyl methacrylate ,Alkyl ,chemistry.chemical_classification ,Acrylate ,Organic Chemistry ,Materials Engineering ,021001 nanoscience & nanotechnology ,poly(methyl methacrylate) ,Poly(methyl methacrylate) ,radical polymerization ,0104 chemical sciences ,transesterification ,chemistry ,visual_art ,graft copolymers ,visual_art.visual_art_medium ,0210 nano-technology ,Physical Chemistry (incl. Structural) - Abstract
A straightforward and efficient synthetic method that transforms poly(methyl methacrylate) (PMMA) into value-added materials is presented. Specifically, PMMA is modified by transesterification to produce a variety of functional copolymers from a single starting material. Key to the reaction is the use of lithium alkoxides, prepared by treatment of primary alcohols with LDA, to displace the methyl esters. Under optimized conditions, up to 65% functionalization was achieved and copolymers containing alkyl, alkene, alkyne, benzyl, and (poly)ether side groups could be prepared. The versatility of this protocol was further demonstrated through the functionalization of both PMMA homo and block copolymers obtained through either radical polymerization (traditional and controlled) or anionic procedures. The scope of this strategy was illustrated by extension to a range of architectures and polymer backbones.
- Published
- 2017
14. Novel Strategy for Photopatterning Emissive Polymer Brushes for Organic Light Emitting Diode Applications
- Author
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Benjaporn Narupai, Zachariah A. Page, Sukrit Mukhopadhyay, Scott Sprague, Christian W. Pester, John W. Kramer, Anatoliy N. Sokolov, Alaina J. McGrath, Peter Trefonas, David S. Laitar, Craig J. Hawker, and Raghida Bou Zerdan
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chemistry.chemical_classification ,Materials science ,Dopant ,Atom-transfer radical-polymerization ,General Chemical Engineering ,Nanotechnology ,02 engineering and technology ,General Chemistry ,Polymer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Photochemistry ,Methacrylate ,01 natural sciences ,0104 chemical sciences ,Indium tin oxide ,lcsh:Chemistry ,lcsh:QD1-999 ,chemistry ,Chemical Sciences ,OLED ,Copolymer ,0210 nano-technology ,Visible spectrum ,Research Article - Abstract
A light-mediated methodology to grow patterned, emissive polymer brushes with micron feature resolution is reported and applied to organic light emitting diode (OLED) displays. Light is used for both initiator functionalization of indium tin oxide and subsequent atom transfer radical polymerization of methacrylate-based fluorescent and phosphorescent iridium monomers. The iridium centers play key roles in photocatalyzing and mediating polymer growth while also emitting light in the final OLED structure. The scope of the presented procedure enables the synthesis of a library of polymers with emissive colors spanning the visible spectrum where the dopant incorporation, position of brush growth, and brush thickness are readily controlled. The chain-ends of the polymer brushes remain intact, affording subsequent chain extension and formation of well-defined diblock architectures. This high level of structure and function control allows for the facile preparation of random ternary copolymers and red–green–blue arrays to yield white emission., Emissive polymer brushes are grafted from conductive substrates via photocatalysis for organic light emitting diode displays. Color tunability, micron pixel features, thickness control, and diblocks are demonstrated.
- Published
- 2017
15. Ultrafast and Ultraslow Oxygen Atom Transfer Reactions between Late Metal Centers
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Seth N. Brown, Olaf Wiest, Kevin C. Fortner, David S. Laitar, Lihung Pu, Sonja B. Braun-Sand, and John Muldoon
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Magnetic Resonance Spectroscopy ,Dimer ,chemistry.chemical_element ,Iridium ,Photochemistry ,Biochemistry ,Catalysis ,Dissociation (chemistry) ,Metal ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Reaction rate constant ,Organometallic Compounds ,Osmium ,Triphenylphosphine ,General Chemistry ,Nuclear magnetic resonance spectroscopy ,Cold Temperature ,Oxygen ,Kinetics ,Crystallography ,chemistry ,Metals ,visual_art ,visual_art.visual_art_medium ,Oxidation-Reduction - Abstract
Oxotrimesityliridium(V), (mes)3Ir=O (mes = 2,4,6-trimethylphenyl), and trimesityliridium(III), (mes)3Ir, undergo extremely rapid degenerate intermetal oxygen atom transfer at room temperature. At low temperatures, the two complexes conproportionate to form (mes)3Ir-O-Ir(mes)3, the 2,6-dimethylphenyl analogue of which has been characterized crystallographically. Variable-temperature NMR measurements of the rate of dissociation of the mu-oxo dimer combined with measurements of the conproportionation equilibrium by low-temperature optical spectroscopy indicate that oxygen atom exchange between iridium(V) and iridium(III) occurs with a rate constant, extrapolated to 20 degrees C, of 5 x 107 M-1 s-1. The oxotris(imido)osmium(VIII) complex (ArN)3Os=O (Ar = 2,6-diisopropylphenyl) also undergoes degenerate intermetal atom transfer to its deoxy partner, (ArN)3Os. However, despite the fact that its metal-oxygen bond strength and reactivity toward triphenylphosphine are nearly identical to those of (mes)3Ir=O, the osmium complex (ArN)3Os=O transfers its oxygen atom 12 orders of magnitude more slowly to (ArN)3Os than (mes)3Ir=O does to (mes)3Ir (kOsOs = 1.8 x 10-5 M-1 s-1 at 20 degrees C). Iridium-osmium cross-exchange takes place at an intermediate rate, in quantitative agreement with a Marcus-type cross relation. The enormous difference between the iridium-iridium and osmium-osmium exchange rates can be rationalized by an analogue of the inner-sphere reorganization energy. Both Ir(III) and Ir(V) are pyramidal and can form pyramidal iridium(IV) with little energetic cost in an orbitally allowed linear approach. Conversely, pyramidalization of the planar tris(imido)osmium(VI) fragment requires placing a pair of electrons in an antibonding orbital. The unique propensity of (mes)3Ir=O to undergo intermetal oxygen atom transfer allows it to serve as an activator of dioxygen in cocatalyzed oxidations, for example, acting with osmium tetroxide to catalyze the aerobic dihydroxylation of monosubstituted olefins and selective oxidation of allyl and benzyl alcohols.
- Published
- 2006
16. Copper(I) β-Boroalkyls from Alkene Insertion: Isolation and Rearrangement
- Author
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and Emily Y. Tsui, Joseph P. Sadighi, and David S. Laitar
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Inorganic Chemistry ,chemistry.chemical_classification ,chemistry ,Stereochemistry ,Alkene ,Organic Chemistry ,chemistry.chemical_element ,Physical and Theoretical Chemistry ,Copper ,Medicinal chemistry - Abstract
The insertion of alkenes into an (NHC)copper(I) boryl affords isolable β-boroalkyl complexes in high yields; competition experiments using substituted styrenes show that electron-donating substituents slow the reaction. Although the insertion products are stable at ambient temperature, a β-hydride elimination/reinsertion sequence affords a rearranged α-boroalkyl complex on heating.
- Published
- 2006
17. Carbon−Carbon Bond Formation on Reaction of a Copper(I) Stannyl Complex with Carbon Dioxide
- Author
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Jacob M. Berlin, David S. Laitar, Joseph P. Sadighi, Jennifer A. Akana, and Koyel X. Bhattacharyya
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chemistry.chemical_classification ,Chemistry ,Organic Chemistry ,chemistry.chemical_element ,Cleavage (embryo) ,Photochemistry ,Medicinal chemistry ,Chloride ,Copper ,Triphenylstannane ,Inorganic Chemistry ,chemistry.chemical_compound ,Deprotonation ,Carbon–carbon bond ,Carbon dioxide ,medicine ,Physical and Theoretical Chemistry ,Electrochemical reduction of carbon dioxide ,medicine.drug - Abstract
The reaction of (IPr)CuOt-Bu (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with triphenylstannane forms a stannyl complex, (IPr)CuSnPh3, by deprotonation of the tin−hydrogen bond. This stannyl complex reacts with CO2 to afford (IPr)CuO2CPh as the sole copper-containing species. A tin−carbon bond in (IPr)CuSnPh3 also undergoes facile cleavage by mild acids such as 2,4-lutidinium chloride.
- Published
- 2008
18. A Carbene-Stabilized Gold(I) Fluoride: Synthesis and Theory
- Author
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and Thomas G. Gray, Joseph P. Sadighi, David S. Laitar, and Peter Müller
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Chemistry ,Ligand ,Organic Chemistry ,Inorganic chemistry ,chemistry.chemical_element ,Inorganic Chemistry ,chemistry.chemical_compound ,Monomer ,Negative charge ,Polymer chemistry ,Fluorine ,Physical and Theoretical Chemistry ,Gold(I) fluoride ,Carbene ,Fluoride - Abstract
The first isolable gold(I) fluoride complex, stabilized by an N-heterocyclic carbene (NHC) ligand, has been isolated in two-coordinate monomeric form. DFT calculations show significant pπ/dπ interactions between fluoride and gold(I) and indicate a substantial negative charge on fluorine.
- Published
- 2005
19. Synthesis, Structure, and Alkyne Reactivity of a Dimeric (Carbene)copper(I) Hydride
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Joseph P. Sadighi, Neal P. Mankad, and David S. Laitar
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chemistry.chemical_classification ,Chemistry ,Hydride ,Organic Chemistry ,Alkyne ,chemistry.chemical_element ,Copper ,Inorganic Chemistry ,chemistry.chemical_compound ,Monomer ,Polymer chemistry ,Triethoxysilane ,Copper hydride ,Organic chemistry ,Reactivity (chemistry) ,Physical and Theoretical Chemistry ,Carbene - Abstract
The monomeric, two-coordinate carbene complex (IPr)CuO-t-Bu (1) (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) reacts readily with silanes such as triethoxysilane, forming a dimeric copper(I) hydride complex (2) with a very short copper−copper distance. Hydrocupration of 3-hexyne by 2 affords a monomeric copper(I) vinyl complex.
- Published
- 2004
20. Synthesis, Structure, and CO2 Reactivity of a Two-Coordinate (Carbene)copper(I) Methyl Complex
- Author
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David S. Laitar, Thomas G. Gray, Joseph P. Sadighi, and Neal P. Mankad
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Denticity ,Stereochemistry ,Ligand ,Organic Chemistry ,chemistry.chemical_element ,Copper ,Inorganic Chemistry ,Co2 reactivity ,chemistry.chemical_compound ,Temperature and pressure ,chemistry ,Yield (chemistry) ,Polymer chemistry ,Physical and Theoretical Chemistry ,Carbene - Abstract
Two-coordinate copper(I) acetate and copper(I) methyl complexes, bearing an N-heterocyclic carbene (NHC) supporting ligand, have been synthesized and structurally characterized, and the stability of the monodentate acetate has been examined by DFT calculations. The methyl complex readily inserts carbon dioxide at ambient temperature and pressure, regenerating the acetate in near-quantitative yield.
- Published
- 2004
21. Copper(I) Complexes of a Heavily Fluorinated β-Diketiminate Ligand: Synthesis, Electronic Properties, and Intramolecular Aerobic Hydroxylation
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Casey J. N. Mathison, Joseph P. Sadighi, David S. Laitar, and William M. Davis
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Stereochemistry ,Ligand ,Metalation ,chemistry.chemical_element ,Infrared spectroscopy ,Copper ,Medicinal chemistry ,Adduct ,Inorganic Chemistry ,Hydroxylation ,chemistry.chemical_compound ,chemistry ,Intramolecular force ,Physical and Theoretical Chemistry ,Benzene - Abstract
The aza-Wittig reaction between Ar(f)()-N=PPh(3) [Ar(f)() = 3,5-(CF(3))(2)C(6)H(3)] and 1,1,1,5,5,5-hexafluoro-2,4-pentanedione affords a new, highly fluorinated beta-diketimine, 1. Metalation by mesitylcopper(I) in benzene gives rise to the Cu(I) beta-diketiminate as its eta(2)-benzene adduct, 2a. Copper(I) carbonyl complexes of 1, and of three less-fluorinated analogues, have been generated in situ and compared by IR spectroscopy; the two backbone CF(3) groups exert a stronger electronic influence than the four N-aryl CF(3) groups. Dinuclear adduct 2b reacts readily with O(2), leading to ortho-hydroxylation of a ligand N-Ar(f)() group.
- Published
- 2003
22. ChemInform Abstract: β-Amidoaldehydes via Oxazoline Hydroformylation
- Author
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Bryan T. Whiting, John W. Kramer, David S. Laitar, Geoffrey W. Coates, and Emil B. Lobkovsky
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chemistry.chemical_compound ,chemistry ,Organic chemistry ,General Medicine ,Oxazoline ,Dicobalt octacarbonyl ,Carbonylation ,Hydroformylation ,Syngas ,Catalysis - Abstract
4-Substituted oxazolines, which are readily synthesized from naturally occurring α-amino acids, are converted efficiently and stereospecifically to β-amidoaldehydes in the presence of synthesis gas and catalytic dicobalt octacarbonyl.
- Published
- 2010
23. Generation of a doubly bridging CO2 ligand and deoxygenation of CO2 by an (NHC)Ni(0) complex
- Author
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Joseph P. Sadighi, Chang Hoon Lee, Peter Mueller, and David S. Laitar
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Ligand ,Stereochemistry ,General Chemistry ,Biochemistry ,Medicinal chemistry ,Catalysis ,law.invention ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,Monomer ,chemistry ,law ,Crystallization ,Deoxygenation - Abstract
The treatment of [(IPr)Ni(μ-Cl)]2 (IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene) with NaOt-Bu and then pinB-Bpin (bis(pinacolato)diboron) gives rise to a mono-NHC−Ni(0) complex, which dimerizes upon crystallization. The same product is prepared by the treatment of [(IPr)Ni(μ-Cl)]2 with Li(BEt)3H, or with NaOt-Bu and then HSi(OEt)3. The treatment of [(IPr)Ni]2 or its monomer with CO2 reduces CO2 to CO generating [(IPr)Ni]2(μ-CO)(μ-η2,η2-CO2). This compound represents an unprecedented symmetric double-bridging mode of CO2.
- Published
- 2007
24. Catalytic Diboration of Aldehydes via Insertion into the Copper—Boron Bond
- Author
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David S. Laitar, Joseph P. Sadighi, and Emily Y. Tsui
- Subjects
chemistry.chemical_classification ,Steric effects ,Addition reaction ,Ligand ,Aryl ,chemistry.chemical_element ,General Chemistry ,General Medicine ,Nuclear magnetic resonance spectroscopy ,Photochemistry ,Biochemistry ,Aldehyde ,Copper ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Polymer chemistry ,Boron - Abstract
Mesitaldehyde reacts cleanly with (IPr)CuB(pin) [IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene); pin = 2,3-dimethyl-2,3-butanediolate] to afford the product complex 1, the first well-defined product of carbonyl group insertion into a metal-boron bond. Analysis of 1 by NMR spectroscopy and single-crystal X-ray diffraction indicates the formation of a copper-carbon and a boron-oxygen bond. A copper(I) precatalyst supported by the less sterically demanding ligand ICy (1,3-dicyclohexylimidazol-2-ylidene) achieves the efficient 1,2-diboration of aryl-, heteroaryl-, and alkyl-substituted aldehydes at room temperature.
- Published
- 2007
25. Oxidation-Resistant, Sterically Demanding Phenanthrolines as Supporting Ligands for Copper(I) Nitrene Transfer Catalysts
- Author
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David S. Laitar, Joseph P. Sadighi, and Charles W. Hamilton
- Subjects
Steric effects ,Chemistry ,Nitrene ,Oxidation resistant ,Polymer chemistry ,Cationic polymerization ,chemistry.chemical_element ,General Medicine ,Copper ,Catalysis - Abstract
New 1,10-phenanthroline ligands have been synthesized with C6F5– or 2,4,6-(CF3)3C6H2– groups in the 2- and 9-positions; a cationic copper(I) complex of the latter catalyses nitrene transfer to the C–H bonds of electron-rich arenes.
- Published
- 2004
26. Stoichiometric and catalytic oxygen activation by trimesityliridium(III)
- Author
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Bridey Grant Jacobi, David S. Laitar, Seth N. Brown, Stephany M. Schuck, Antonio G. Dipasquale, Lihung Pu, Michael F. Wargocki, and Kevin C. Fortner
- Subjects
Triphenylarsine ,chemistry.chemical_element ,Photochemistry ,Oxygen ,Medicinal chemistry ,Catalysis ,Inorganic Chemistry ,NMR spectra database ,chemistry.chemical_compound ,chemistry ,Iridium ,Physical and Theoretical Chemistry ,Triphenylphosphine ,Triphenylphosphine oxide ,Stoichiometry - Abstract
Trimesityliridium(III) (mesityl = 2,4,6-trimethylphenyl) reacts with O(2) to form oxotrimesityliridium(V), (mes)(3)Ir=O, in a reaction that is cleanly second order in iridium. In contrast to initial reports by Wilkinson, there is no evidence for substantial accumulation of an intermediate in this reaction. The oxo complex (mes)(3)Ir=O oxidizes triphenylphosphine to triphenylphosphine oxide in a second-order reaction with DeltaH++ = 10.04 +/- 0.16 kcal/mol and DeltaS++ = -21.6 +/- 0.5 cal/(mol.K) in 1,2-dichloroethane. Triphenylarsine is also oxidized, though over an order of magnitude more slowly. Ir(mes)(3) binds PPh(3) reversibly (K(assoc) = 84 +/- 3 M(-1) in toluene at 20 degrees C) to form an unsymmetrical, sawhorse-shaped four-coordinate complex, whose temperature-dependent NMR spectra reveal a variety of dynamic processes. Oxygen atom transfer from (mes)(3)Ir=O and dioxygen activation by (mes)(3)Ir can be combined to allow catalytic aerobic oxidations of triphenylphosphine at room temperature and atmospheric pressure with overall activity (approximately 60 turnovers/h) comparable to the fastest reported catalysts. A kinetic model that uses the rates measured for dioxygen activation, atom transfer, and phosphine binding describes the observed catalytic behavior well. Oxotrimesityliridium does not react with sulfides, sulfoxides, alcohols, or alkenes, apparently for kinetic reasons.
- Published
- 2002
27. Efficient Homogeneous Catalysis in the Reduction of CO2 to CO
- Author
-
Peter Müller, Joseph P. Sadighi, and David S. Laitar
- Subjects
Ligand ,Stereochemistry ,chemistry.chemical_element ,Selective catalytic reduction ,Homogeneous catalysis ,General Chemistry ,Biochemistry ,Copper ,Medicinal chemistry ,Catalysis ,chemistry.chemical_compound ,Colloid and Surface Chemistry ,chemistry ,Reagent ,Alkoxide ,Stoichiometry - Abstract
The well-defined copper(I) boryl complex [(IPr)Cu(Bpin)] [where IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene, and pin = pinacolate: 2,3-dimethyl-2,3-butanediolate] deoxygenates CO2 rapidly and quantitatively, affording CO and the borate complex [(IPr)Cu(OBpin)]. The boryl may be regenerated by treatment with the diboron compound pinB-Bpin, giving the stable byproduct pinB-O-Bpin. The use of a copper(I) alkoxide precatalyst and stoichiometric diboron reagent results in catalytic reduction of CO2, with high turnover numbers (1000 per Cu) and frequencies (100 per Cu in 1 h) depending on supporting ligand and reaction conditions.
- Published
- 2005
28. β-Amidoaldehydes via oxazoline hydroformylation
- Author
-
Geoffrey W. Coates, John W. Kramer, Bryan T. Whiting, David S. Laitar, and Emil B. Lobkovsky
- Subjects
Aldehydes ,Molecular Conformation ,Metals and Alloys ,Stereoisomerism ,Cobalt ,General Chemistry ,Oxazoline ,Catalysis ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,chemistry.chemical_compound ,chemistry ,Materials Chemistry ,Ceramics and Composites ,Organic chemistry ,Gases ,Dicobalt octacarbonyl ,Oxazoles ,Hydroformylation ,Syngas - Abstract
4-Substituted oxazolines, which are readily synthesized from naturally occurring alpha-amino acids, are converted efficiently and stereospecifically to beta-amidoaldehydes in the presence of synthesis gas and catalytic dicobalt octacarbonyl.
- Published
- 2009
29. Cu-Catalyzed Catalytic Diboration of Aldehydes
- Author
-
David S. Laitar, Emily Y. Tsui, and Joseph P. Sadighi
- Subjects
Chemistry ,Organic chemistry ,Catalysis - Published
- 2006
30. Carbon−Carbon Bond Formation on Reaction of a Copper(I) Stannyl Complex with Carbon Dioxide.
- Author
-
Koyel X. Bhattacharyya, Jennifer A. Akana, David S. Laitar, Jacob M. Berlin, and Joseph P. Sadighi
- Published
- 2008
- Full Text
- View/download PDF
31. Oxidation-resistant, sterically demanding phenanthrolines as supporting ligands for copper(i) nitrene transfer catalysts.
- Author
-
Charles W. Hamilton, David S. Laitar, and Joseph P. Sadighi
- Published
- 2004
Catalog
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