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Vacuum-Assisted Sorbent Extraction: An Analytical Methodology For The Determination Of Ultraviolet Filters In Environmental Samples, María Trujillo-Rodríguez, Jared L. Anderson, Sage J. B. Dunham, Victoria L. Noad, Daniel B. Cardin 2019 Iowa State University

Vacuum-Assisted Sorbent Extraction: An Analytical Methodology For The Determination Of Ultraviolet Filters In Environmental Samples, María Trujillo-Rodríguez, Jared L. Anderson, Sage J. B. Dunham, Victoria L. Noad, Daniel B. Cardin

Jared L. Anderson

Vacuum-assisted sorbent extraction (VASE) has been applied for the first time in the determination of UV filters in water samples in combination with gas chromatography-mass spectrometry. VASE is a variant of headspace extraction which was developed in conjunction with the sorbent pen (SP) technology. This technique combines the advantages of both stir-bar assisted extraction and headspace solid-phase microextraction. The SP traps allowed both reduced pressure in-vial extraction and direct thermal desorption via a unique gas chromatographic injection port. The main parameters that affect the performance of VASE, including both extraction and desorption conditions, were extensively optimized. Under optimum conditions, extraction ...


Syntheses, Characterization, And Preliminary Evaluation Of Potential Ruthenium Anticancer Complexes Containing Schiff Base Ligands, Stephen Mensah 2019 Illinois State University

Syntheses, Characterization, And Preliminary Evaluation Of Potential Ruthenium Anticancer Complexes Containing Schiff Base Ligands, Stephen Mensah

Theses and Dissertations

Platinum-based drugs have over the years been administered in the treatment of tumours.

Unfortunately, platinum resistance and the severe side effects associated with the treatments has necessitated the research for new anti-cancer drugs. Ruthenium(II) and Ruthenium(III) complexes have shown promise as useful alternative anticancer agents. The lead candidates include the Ru(II) complex RAPTA-C, a ruthenium(II)-arene complex [Ru(η6-p-cymene)Cl2(1,3,5-triaza-7-phosphaadamantane)] and the Ru(III) complex NAMI-A [imidazoleH][trans-Ru(imidazole) (dimethyl sulfoxide)Cl4]. Both compounds have shown potent cytotoxic activity in several primary human tumor models. Unfortunately, NAMI-A could not advance in clinical evaluations ...


Loss Of Scribble Confers Cisplatin Resistance During Nsclc Chemotherapy Via Nox2/Ros And Nrf2/Pd-L1 Signaling, Na Wang, Lele Song, Yi Xu, Longfu Zhang, Yanjun Wu, Jingyu Guo, Weiwei Ji, Li Li Ph.D., Jingya Zhao, Xin Zhang, Lixing Zhan 2019 Molloy College

Loss Of Scribble Confers Cisplatin Resistance During Nsclc Chemotherapy Via Nox2/Ros And Nrf2/Pd-L1 Signaling, Na Wang, Lele Song, Yi Xu, Longfu Zhang, Yanjun Wu, Jingyu Guo, Weiwei Ji, Li Li Ph.D., Jingya Zhao, Xin Zhang, Lixing Zhan

Li Li

Background: Cisplatin resistance remains a major clinical obstacle to the successful treatment of non-small cell lung cancer (NSCLC). Scribble contributes to ROS-induced inflammation and cisplatin-elevated toxic reactive oxygen species (ROS) promotes cell death. However, it is unknown whether and how Scribble is involved in the cisplatin-related cell death and the underlying mechanism of Scribble in response to chemotherapies and in the process of oxidative stress in NSCLC. Methods: We used two independent cohorts of NSCLC samples derived from patients treated with platinumcontaining chemotherapy and xenograft modeling in vivo. We analyzed the correlation between Scribble and Nox2 or Nrf2/PD-L1 both ...


A Diffraction Paradox: An Unusually Broad Diffraction Background Signals Ideal Graphene, Shen Chen, Michael Horn-von Hoegen, Patricia A. Thiel, Michael C. Tringides 2019 Iowa State University and Ames Laboratory

A Diffraction Paradox: An Unusually Broad Diffraction Background Signals Ideal Graphene, Shen Chen, Michael Horn-Von Hoegen, Patricia A. Thiel, Michael C. Tringides

Patricia A. Thiel

The realization of the unusual properties of 2-d materials requires the formation of large domains of single layer thickness, extending over the mesoscale. It is found that the formation of ideal graphene on SiC, contrary to textbook diffraction , is signaled by a strong bell-shaped-component (BSC) around the (00) and G(10), but not the SiC(10) spots.The BSC is also seen for graphene on metals, because single layer uniform graphene with large lateral size can also be grown. It is only seen by electron diffraction and not with X-ray or He-scattering experiments. Most likely it originates from the spatial ...


Co-Localization Of Dna I-Motif-Forming Sequences And 5-Hydroxymethyl-Cytosines In Human Embryonic Stem Cells, Yogini P. Bhavsar-Jog, Eric Van Dornshuld, Tracy A. Brooks, Gregory S. Tschumper, Randy M. Wadkins 2019 University of Mississippi

Co-Localization Of Dna I-Motif-Forming Sequences And 5-Hydroxymethyl-Cytosines In Human Embryonic Stem Cells, Yogini P. Bhavsar-Jog, Eric Van Dornshuld, Tracy A. Brooks, Gregory S. Tschumper, Randy M. Wadkins

Faculty and Student Publications

G-quadruplexes (G4s) and i-motifs (iMs) are tetraplex DNA structures. Sequences capable of forming G4/iMs are abundant near the transcription start sites (TSS) of several genes. G4/iMs affect gene expression in vitro. Depending on the gene, the presence of G4/iMs can enhance or suppress expression, making it challenging to discern the underlying mechanism by which they operate. Factors affecting G4/iM structures can provide additional insight into their mechanism of regulation. One such factor is epigenetic modification. The 5-hydroxymethylated cytosines (5hmCs) are epigenetic modifications that occur abundantly in human embryonic stem cells (hESC). The 5hmCs, like G4/iMs ...


High Throughput Screening Of 3d Printable Resins: Adjusting The Surface And Catalytic Properties Of Multifunctional Architectures, J. Sebastián Manzano, Hsin Wang, Igor I. Slowing 2019 Iowa State University and Ames Laboratory

High Throughput Screening Of 3d Printable Resins: Adjusting The Surface And Catalytic Properties Of Multifunctional Architectures, J. Sebastián Manzano, Hsin Wang, Igor I. Slowing

Igor I. Slowing

Identification of 3D printable materials is crucial to expand the breadth of physical and chemical properties attainable by additive manufacturing. Stereolithography (SLA), a widespread 3D printing method based on resin photo-polymerization, is ideally suited for exploring a large variety of monomers to produce functional three-dimensional solids of diverse properties. However, for most of the commercially available SLA 3D printers, screening monomers and resin compositions requires large volumes (~150 mL) in each printing cycle, making the process costly and inefficient. Herein, a high throughput block (HTB) adaptor was developed to screen arrays of monomers and resin compositions, consuming lower volumes (< 2 mL) and less time per print (< 1/16 based on a 44 matrix) than using the original hardware. Using this approach, a library of materials with different surface hydrophobicities were 3D printed by including long chain acrylates in the resins. In addition, several metal salts were dissolved in an acrylic acid-based resin, 3D printed and screened as heterogeneous catalysts for the selective aerobic oxidation of benzyl alcohol to benzaldehyde. Cu(II)-based resins produced the most active structures. Combinations of Cu(II) and long chain acrylate monomers were then used to 3D print complex catalytic architectures with varying degrees of hydrophobicity. Linear relationships were observed between 3D printed surface area, surface hydrophobicity and catalyst performance. For a high surface Schwarz P topology ca. 60 % enhancement in the catalytic activity of Cu(II) was attained by replacing the parent resin with one containing hydrophobic isodecyl groups, indicating that the immediate environment of the catalytic site affected its performance. The HTB enables fast screening of resins for 3D printing multifunctional architectures with intrinsic catalytic activity, tunable surface properties, and minimal waste.


Nextgen Advises "Trying To Manage", Douglass Steinhauff, Joel Henrique Ellwanger, Monika Lewinska, Edmond Sanganyado, Yongsheng Ji, Buddini Iroshika Karawdeniya, Naike Bochatay, Eric Britt Moore, Aminata Coulibaly, Shaima Ibrahim, Déna Skye Jansen, Joshua I. James, David M. Cole, Anna Lipkin, Beth McKinnon Adamowicz, Science Management Associates, Shervin Fatehi, Maria Helena Holmstrom, Rosa Li 2019 University of Utah

Nextgen Advises "Trying To Manage", Douglass Steinhauff, Joel Henrique Ellwanger, Monika Lewinska, Edmond Sanganyado, Yongsheng Ji, Buddini Iroshika Karawdeniya, Naike Bochatay, Eric Britt Moore, Aminata Coulibaly, Shaima Ibrahim, Déna Skye Jansen, Joshua I. James, David M. Cole, Anna Lipkin, Beth Mckinnon Adamowicz, Science Management Associates, Shervin Fatehi, Maria Helena Holmstrom, Rosa Li

Chemistry Faculty Publications and Presentations

Peer mentors can provide crucial support to young scientists by asking questions to facilitate further reflection, assuring mentees that they are not alone, and suggesting potential next steps. We asked our readers to act as peer mentors to “Trying to Manage,” the anonymous student who posed the question above. Follow NextGen Voices on Twitter with hashtag #NextGenSci. Read previous NextGen Voices survey results at https://science.sciencemag.org/collection/nextgen-voices. —Jennifer Sills


Microwave Solventless Synthesis Of Meso-Tetrakis (Pentafluorophenyl)Poprphyrin (Tppf20) And Tris(Pentafluorophenyl))Corrole [Chemistry], Sunaina Singh 2019 CUNY La Guardia Community College

Microwave Solventless Synthesis Of Meso-Tetrakis (Pentafluorophenyl)Poprphyrin (Tppf20) And Tris(Pentafluorophenyl))Corrole [Chemistry], Sunaina Singh

Open Educational Resources

Organic chemistry is a two-semester course (Organic Chemistry I, SCC 251 and Organic Chemistry II, SCC 252) required for majors in Biology. The SCC 251 course has been designated for the Integrative Learning Core Competency as well the Digital Communication Ability. This course emphasizes the synthesis, structure, reactivity, and mechanisms of reaction of organic compounds. Laboratory stresses various organic synthetic and analytic techniques (distillation, extraction, chromatography and spectroscopy).

This lab provided an opportunity for students to go deeper with the chemistry content by correlating to the concepts they learned in General Chemistry courses such as Valence shell electron pair repulsion ...


Titration Of A Newtown Creek Environmental Water Sample To Determine The Amount Of Chloride Ions [Chemistry], Kevin Mark 2019 CUNY La Guardia Community College

Titration Of A Newtown Creek Environmental Water Sample To Determine The Amount Of Chloride Ions [Chemistry], Kevin Mark

Open Educational Resources

Main Course Learning Objectives:

The General Chemistry 1 (SCC 201) course has multiple course learning objectives, which articulate key introductory chemistry concepts that all STEM students should possess. In particular, the Newtown Creek titration experiment aligns with SCC 201 learning objectives of:

  1. Demonstrate an appreciation of the role of chemistry in various aspects of life
  2. Perform basic laboratory skills such as the proper execution of titration techniques
  3. Describe and explain the fundamental chemistry concept of solution concentration
  4. Analyze and represent experimental data in tables and graphs, interpret experimental results and write laboratory reports

In the SCC 201 laboratory, students are ...


Theoretical Studies Of Ir And Nmr Spectral Changes Induced By Sigma-Hole Hydrogen, Halogen, Chalcogen, Pnicogen, And Tetrel Bonds In A Model Protein Environment, Mariusz Michalczyk, Wiktor Zierkiewicz, Rafał Wysokiński, Steve Scheiner 2019 Wrocław University of Science and Technology

Theoretical Studies Of Ir And Nmr Spectral Changes Induced By Sigma-Hole Hydrogen, Halogen, Chalcogen, Pnicogen, And Tetrel Bonds In A Model Protein Environment, Mariusz Michalczyk, Wiktor Zierkiewicz, Rafał Wysokiński, Steve Scheiner

Steve Scheiner

Various types of σ-hole bond complexes were formed with FX, HFY, H2FZ, and H3FT (X = Cl, Br, I; Y = S, Se, Te; Z = P, As, Sb; T = Si, Ge, Sn) as Lewis acid. In order to examine their interactions with a protein, N-methylacetamide (NMA), a model of the peptide linkage was used as the base. These noncovalent bonds were compared by computational means with H-bonds formed by NMA with XH molecules (X = F, Cl, Br, I). In all cases, the A–F bond, which lies opposite the base and is responsible for the σ-hole on the ...


Synthesis And Evaluation Of Novel Silica Hydride-Based Stationary Phases For Bioanalytical Applications, Seiichiro Watanabe 2019 San José State University

Synthesis And Evaluation Of Novel Silica Hydride-Based Stationary Phases For Bioanalytical Applications, Seiichiro Watanabe

Seiichiro Watanabe

Most HPLC columns are packed with silanol (Si-OH)-rich type-B silica that often
participates in undesired electrostatic interactions with sample solutes and produces a poor analyte peak shape. These silanols are also known to facilitate the surface hydration required for HILIC mode to retain polar analytes. However, the hydrated surface composition can easily fluctuate, which results in poor reproducibility and requires a lengthy equilibration step. In this study, four novel stationary phases have been developed by using the TYPE-CTM silica material, in which up to 95% of the surface silanols have been replaced with Si-H group. One of the advantages ...


High Throughput Screening Of 3d Printable Resins: Adjusting The Surface And Catalytic Properties Of Multifunctional Architectures, J. Sebastián Manzano, Hsin Wang, Igor I. Slowing 2019 Iowa State University and Ames Laboratory

High Throughput Screening Of 3d Printable Resins: Adjusting The Surface And Catalytic Properties Of Multifunctional Architectures, J. Sebastián Manzano, Hsin Wang, Igor I. Slowing

Chemistry Publications

Identification of 3D printable materials is crucial to expand the breadth of physical and chemical properties attainable by additive manufacturing. Stereolithography (SLA), a widespread 3D printing method based on resin photo-polymerization, is ideally suited for exploring a large variety of monomers to produce functional three-dimensional solids of diverse properties. However, for most of the commercially available SLA 3D printers, screening monomers and resin compositions requires large volumes (~150 mL) in each printing cycle, making the process costly and inefficient. Herein, a high throughput block (HTB) adaptor was developed to screen arrays of monomers and resin compositions, consuming lower volumes (< 2 mL) and less time per print (< 1/16 based on a 44 matrix) than using the original hardware. Using this approach, a library of materials with different surface hydrophobicities were 3D printed by including long chain acrylates in the resins. In addition, several metal salts were dissolved in an acrylic acid-based resin, 3D printed and screened as heterogeneous catalysts for the selective aerobic oxidation of benzyl alcohol to benzaldehyde. Cu(II)-based resins produced the most active structures. Combinations of Cu(II) and long chain acrylate monomers were then used to 3D print complex catalytic architectures with varying degrees of hydrophobicity. Linear relationships were observed between 3D printed surface area, surface hydrophobicity and catalyst performance. For a high surface Schwarz P topology ca. 60 % enhancement in the catalytic activity of Cu(II) was attained by replacing the parent resin with one containing hydrophobic isodecyl groups, indicating that the immediate environment of the catalytic site affected its performance. The HTB enables fast screening of resins for 3D printing multifunctional architectures with intrinsic catalytic activity, tunable surface properties, and minimal waste.


Effects Of Biradical Deuteration On The Performance Of Dnp: Towards Better Performing Polarizing Agents, Frédéric A. Perras, Regina R. Reinig, Igor I. Slowing, Aaron D. Sadow, Marek Pruski 2019 Ames Laboratory

Effects Of Biradical Deuteration On The Performance Of Dnp: Towards Better Performing Polarizing Agents, Frédéric A. Perras, Regina R. Reinig, Igor I. Slowing, Aaron D. Sadow, Marek Pruski

Igor I. Slowing

We study the effects of the deuteration of biradical polarizing agents on the efficiency of dynamic nuclear polarization (DNP) via the cross-effect. To this end, we synthesized a series of bTbK and TOTAPol biradicals with systematically increased deuterium substitution. The deuteration increases the radicals' relaxation time, thus contributing to a higher saturation factor and larger DNP enhancement, and reduces the pool of protons within the so-called spin diffusion barrier. Notably, we report that full or partial deuteration leads to improved DNP enhancement factors in standard samples, but also slows down the build-up of hyperpolarization. Improvements in DNP enhancements factors of ...


Homoleptic Trivalent Tris(Alkyl) Rare Earth Compounds, Aradhana Pindwal, KaKing Yan, Smita Patnaik, Bradley M. Schmidt, Arkady Ellern, Igor I. Slowing, Cheolbeom Bae, Aaron D. Sadow 2019 Iowa State University and Ames Laboratory

Homoleptic Trivalent Tris(Alkyl) Rare Earth Compounds, Aradhana Pindwal, Kaking Yan, Smita Patnaik, Bradley M. Schmidt, Arkady Ellern, Igor I. Slowing, Cheolbeom Bae, Aaron D. Sadow

Igor I. Slowing

Homoleptic tris(alkyl) rare earth complexes Ln{C(SiHMe2)(3)}(3) (Ln = La, 1a; Ce, 1b; Pr, 1c; Nd, 1d) are synthesized in high yield from LnI(3)THF(n) and 3 equiv of KC(SiHMe2)(3). X-ray diffraction studies reveal 1a-d are isostructural, pseudo-C-3-symmetric molecules that contain two secondary Li <- HSi interactions per alkyl ligand (six total). Spectroscopic assignments are supported by comparison with Ln{C(SiDMe2)(3)}(3) and DFT calculations. The Ln <- HSi and terminal SiH exchange rapidly on the NMR time scale at room temperature, but the two motifs are resolved at low temperature. Variable-temperature NMR studies provide activation parameters for the exchange process in la (Delta H-double dagger = 8.2(4) kcal.mol(-1); Delta S-double dagger = -1(2) cal.mol(-1)K(-1)) and 1a-d(9) (Delta H-double dagger = 7.7(3) kcal.mol(-1); Delta S-double dagger = -4(2) cal.mol(-1)K(-1)). Comparisons of lineshapes, rate constants, (k(H)/k(D)), and slopes of ln (k/T) vs 1/T plots for la and 1a-d(9) reveal that an inverse isotope effect dominates at low temperature. DFT calculations identify four low-energy intermediates containing five beta-Si-H -> Ln and one gamma-C-H -> Ln. The calculations also suggest the pathway for Ln <- HSi/SiH exchange involves rotation of a single C(SiHMe2)(3) ligand that is coordinated to the Ln center through the Ln-C bond and one secondary interaction. These robust organometallic compounds persist in solution and in the solid state up to 80 degrees C, providing potential for their use in a range of synthetic applications. For example, reactions of Ln{C(SiHMe2)(3)}(3) and ancillary proligands, such as bis-1,1-(4,4-dimethyl-2-oxazolinyl)ethane (HMeC(Ox(Me2))(2)) give {MeC(Ox(Me2))(2)}Ln{C(SiHMe2)(3)}(2), and reactions with disilazanes provide solvent-free lanthanoid tris(disilazides).


Virtual Special Issue On Catalysis At The U.S. Department Of Energy’S National Laboratories, Marek Pruski, Aaron D. Sadow, Igor I. Slowing, Christopher L. Marshall, Peter Stair, Jose Rodriguez, Alex Harris, Gabor A. Somorjai, Juergen Biener, Christopher Matranga, Congjun Wang, Joshua A. Schaidle, Gregg T. Beckham, Daniel A. Ruddy, Todd Deutsch, Shaun M. Alia, Chaitanya Narula, Steve Overbury, Todd Toops, R. Morris Bullock, Charles H. F. Peden, Yong Wang, Mark D. Allendorf, Jens Nørskov, Thomas Bligaard 2019 Ames Laboratory

Virtual Special Issue On Catalysis At The U.S. Department Of Energy’S National Laboratories, Marek Pruski, Aaron D. Sadow, Igor I. Slowing, Christopher L. Marshall, Peter Stair, Jose Rodriguez, Alex Harris, Gabor A. Somorjai, Juergen Biener, Christopher Matranga, Congjun Wang, Joshua A. Schaidle, Gregg T. Beckham, Daniel A. Ruddy, Todd Deutsch, Shaun M. Alia, Chaitanya Narula, Steve Overbury, Todd Toops, R. Morris Bullock, Charles H. F. Peden, Yong Wang, Mark D. Allendorf, Jens Nørskov, Thomas Bligaard

Igor I. Slowing

Catalysis research at the U.S. Department of Energy’s (DOE’s) National Laboratories covers a wide range of research topics in heterogeneous catalysis, homogeneous/molecular catalysis, biocatalysis, electrocatalysis, and surface science. Since much of the work at National Laboratories is funded by DOE, the research is largely focused on addressing DOE’s mission to ensure America’s security and prosperity by addressing its energy, environmental, and nuclear challenges through transformative science and technology solutions. The catalysis research carried out at the DOE National Laboratories ranges from very fundamental catalysis science, funded by DOE’s Office of Basic Energy Sciences ...


Oxygen Insertion Reactions Of Mixed N-Heterocyclic Carbene–Oxazolinylborato Zinc Alkyl Complexes, Songchen Xu, William C. Everett, Arkady Ellern, Theresa L. Windus, Aaron D. Sadow 2019 Iowa State University

Oxygen Insertion Reactions Of Mixed N-Heterocyclic Carbene–Oxazolinylborato Zinc Alkyl Complexes, Songchen Xu, William C. Everett, Arkady Ellern, Theresa L. Windus, Aaron D. Sadow

Theresa Windus

We report the synthesis of a new mixed oxazoline–carbene scorpionate ligand, bis(4,4-dimethyl-2-oxazolinyl)(1-mesitylimidazolyl)phenylborate (PhB(OxMe2)2ImMes). Reactions of the protonated form PhB(OxMe2)2(ImMesH) with dialkylzinc compounds provide four-coordinate zinc alkyl complexes, and X-ray diffraction studies of the {PhB(OxMe2)2ImMes}ZnR (R = Me, Et) compounds show significant structural distortions involving the R groups shifting away from the carbene donor. The reaction of {PhB(OxMe2)2ImMes}ZnEt (3) and O2 provides an isolable mononuclear zinc alkylperoxide {PhB(OxMe2)2ImMes}ZnOOEt (4), which has been characterized by single crystal X-ray diffraction and 17O NMR spectroscopy.


Oxygen Insertion Reactions Of Mixed N-Heterocyclic Carbene–Oxazolinylborato Zinc Alkyl Complexes, Songchen Xu, William C. Everett, Arkady Ellern, Theresa L. Windus, Aaron D. Sadow 2019 Iowa State University

Oxygen Insertion Reactions Of Mixed N-Heterocyclic Carbene–Oxazolinylborato Zinc Alkyl Complexes, Songchen Xu, William C. Everett, Arkady Ellern, Theresa L. Windus, Aaron D. Sadow

Aaron D. Sadow

We report the synthesis of a new mixed oxazoline–carbene scorpionate ligand, bis(4,4-dimethyl-2-oxazolinyl)(1-mesitylimidazolyl)phenylborate (PhB(OxMe2)2ImMes). Reactions of the protonated form PhB(OxMe2)2(ImMesH) with dialkylzinc compounds provide four-coordinate zinc alkyl complexes, and X-ray diffraction studies of the {PhB(OxMe2)2ImMes}ZnR (R = Me, Et) compounds show significant structural distortions involving the R groups shifting away from the carbene donor. The reaction of {PhB(OxMe2)2ImMes}ZnEt (3) and O2 provides an isolable mononuclear zinc alkylperoxide {PhB(OxMe2)2ImMes}ZnOOEt (4), which has been characterized by single crystal X-ray diffraction and 17O NMR spectroscopy.


Virtual Special Issue On Catalysis At The U.S. Department Of Energy’S National Laboratories, Marek Pruski, Aaron D. Sadow, Igor I. Slowing, Christopher L. Marshall, Peter Stair, Jose Rodriguez, Alex Harris, Gabor A. Somorjai, Juergen Biener, Christopher Matranga, Congjun Wang, Joshua A. Schaidle, Gregg T. Beckham, Daniel A. Ruddy, Todd Deutsch, Shaun M. Alia, Chaitanya Narula, Steve Overbury, Todd Toops, R. Morris Bullock, Charles H. F. Peden, Yong Wang, Mark D. Allendorf, Jens Nørskov, Thomas Bligaard 2019 Ames Laboratory

Virtual Special Issue On Catalysis At The U.S. Department Of Energy’S National Laboratories, Marek Pruski, Aaron D. Sadow, Igor I. Slowing, Christopher L. Marshall, Peter Stair, Jose Rodriguez, Alex Harris, Gabor A. Somorjai, Juergen Biener, Christopher Matranga, Congjun Wang, Joshua A. Schaidle, Gregg T. Beckham, Daniel A. Ruddy, Todd Deutsch, Shaun M. Alia, Chaitanya Narula, Steve Overbury, Todd Toops, R. Morris Bullock, Charles H. F. Peden, Yong Wang, Mark D. Allendorf, Jens Nørskov, Thomas Bligaard

Aaron D. Sadow

Catalysis research at the U.S. Department of Energy’s (DOE’s) National Laboratories covers a wide range of research topics in heterogeneous catalysis, homogeneous/molecular catalysis, biocatalysis, electrocatalysis, and surface science. Since much of the work at National Laboratories is funded by DOE, the research is largely focused on addressing DOE’s mission to ensure America’s security and prosperity by addressing its energy, environmental, and nuclear challenges through transformative science and technology solutions. The catalysis research carried out at the DOE National Laboratories ranges from very fundamental catalysis science, funded by DOE’s Office of Basic Energy Sciences ...


Homoleptic Trivalent Tris(Alkyl) Rare Earth Compounds, Aradhana Pindwal, KaKing Yan, Smita Patnaik, Bradley M. Schmidt, Arkady Ellern, Igor I. Slowing, Cheolbeom Bae, Aaron D. Sadow 2019 Iowa State University and Ames Laboratory

Homoleptic Trivalent Tris(Alkyl) Rare Earth Compounds, Aradhana Pindwal, Kaking Yan, Smita Patnaik, Bradley M. Schmidt, Arkady Ellern, Igor I. Slowing, Cheolbeom Bae, Aaron D. Sadow

Aaron D. Sadow

Homoleptic tris(alkyl) rare earth complexes Ln{C(SiHMe2)(3)}(3) (Ln = La, 1a; Ce, 1b; Pr, 1c; Nd, 1d) are synthesized in high yield from LnI(3)THF(n) and 3 equiv of KC(SiHMe2)(3). X-ray diffraction studies reveal 1a-d are isostructural, pseudo-C-3-symmetric molecules that contain two secondary Li <- HSi interactions per alkyl ligand (six total). Spectroscopic assignments are supported by comparison with Ln{C(SiDMe2)(3)}(3) and DFT calculations. The Ln <- HSi and terminal SiH exchange rapidly on the NMR time scale at room temperature, but the two motifs are resolved at low temperature. Variable-temperature NMR studies provide activation parameters for the exchange process in la (Delta H-double dagger = 8.2(4) kcal.mol(-1); Delta S-double dagger = -1(2) cal.mol(-1)K(-1)) and 1a-d(9) (Delta H-double dagger = 7.7(3) kcal.mol(-1); Delta S-double dagger = -4(2) cal.mol(-1)K(-1)). Comparisons of lineshapes, rate constants, (k(H)/k(D)), and slopes of ln (k/T) vs 1/T plots for la and 1a-d(9) reveal that an inverse isotope effect dominates at low temperature. DFT calculations identify four low-energy intermediates containing five beta-Si-H -> Ln and one gamma-C-H -> Ln. The calculations also suggest the pathway for Ln <- HSi/SiH exchange involves rotation of a single C(SiHMe2)(3) ligand that is coordinated to the Ln center through the Ln-C bond and one secondary interaction. These robust organometallic compounds persist in solution and in the solid state up to 80 degrees C, providing potential for their use in a range of synthetic applications. For example, reactions of Ln{C(SiHMe2)(3)}(3) and ancillary proligands, such as bis-1,1-(4,4-dimethyl-2-oxazolinyl)ethane (HMeC(Ox(Me2))(2)) give {MeC(Ox(Me2))(2)}Ln{C(SiHMe2)(3)}(2), and reactions with disilazanes provide solvent-free lanthanoid tris(disilazides).


Effects Of Biradical Deuteration On The Performance Of Dnp: Towards Better Performing Polarizing Agents, Frédéric A. Perras, Regina R. Reinig, Igor I. Slowing, Aaron D. Sadow, Marek Pruski 2019 Ames Laboratory

Effects Of Biradical Deuteration On The Performance Of Dnp: Towards Better Performing Polarizing Agents, Frédéric A. Perras, Regina R. Reinig, Igor I. Slowing, Aaron D. Sadow, Marek Pruski

Aaron D. Sadow

We study the effects of the deuteration of biradical polarizing agents on the efficiency of dynamic nuclear polarization (DNP) via the cross-effect. To this end, we synthesized a series of bTbK and TOTAPol biradicals with systematically increased deuterium substitution. The deuteration increases the radicals' relaxation time, thus contributing to a higher saturation factor and larger DNP enhancement, and reduces the pool of protons within the so-called spin diffusion barrier. Notably, we report that full or partial deuteration leads to improved DNP enhancement factors in standard samples, but also slows down the build-up of hyperpolarization. Improvements in DNP enhancements factors of ...


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