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At least 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Geranylgeranylated-chlorophyll-protein complexes in lhl3 mutant of the green alga Chlamydomonas reinhardtii

Chlorophylls a and b (Chl a and b) are involved in light harvesting, photochemical reactions, and electron transfer reactions in plants and green algae. The core complexes of the photosystems (PSI and PSII) associate with Chl a, while the peripheral antenna complexes (LHCI and LHCII) bind Chls a and b. One of the final steps of Chl biosynthesis is the conversion of geranylgeranylated Chls (Chls GG ) to phytylated Chls by geranylgeranyl reductase (GGR). Here, we isolated and characterized a pale green mutant of the green alga Chlamydomonas reinhardtii that was very photosensitive and was unable to grow photoautotrophically. This mutant has a 16-bp deletion in the LHL3 gene, which resulted in the loss of LHL3 and GGR and accumulated only Chls GG . The lhl3 mutant cells grown in the dark accumulated PSII and PSI proteins at 25–50% of WT levels, lacked PSII activity, and retained a decreased PSI activity. The PSII and PSI proteins were depleted to trace amounts in the mutant cells grown in light. In contrast, the accumulation of LHCI and LHCII was unaffected except for LHCA3. Our results suggest that the replacement of Chls with Chls GG strongly affects the structural and functional integrity of PSII and PSI complexes but their associating LHC complexes to a lesser extent. Affinity purification of HA-tagged LHL3 confirmed the formation of a stable LHL3-GGR complex, which is vital for GGR stability. The LHL3-GGR complex contained a small amount of PSI complex assembly factors, suggesting a putative coupling between Chl synthesis and PSI complex assembly.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2023

Assessing complexity and dynamics in epidemics: geographical barriers and facilitators of foot-and-mouth disease dissemination

Introduction: Physical and non-physical processes that occur in nature may influence biological processes, such as dissemination of infectious diseases. However, such processes may be hard to detect when they are complex systems. Because complexity is a dynamic and non-linear interaction among numerous elements and structural levels in which specific effects are not necessarily linked to any one specific element, cause-effect connections are rarely or poorly observed. Methods: To test this hypothesis, the complex and dynamic properties of geo-biological data were explored with high-resolution epidemiological data collected in the 2001 Uruguayan foot-and-mouth disease (FMD) epizootic that mainly affected cattle. County-level data on cases, farm density, road density, river density, and the ratio of road (or river) length/county perimeter were analyzed with an open-ended procedure that identified geographical clustering in the first 11 epidemic weeks. Two questions were asked: (i) do geo-referenced epidemiologic data display complex properties? and (ii) can such properties facilitate or prevent disease dissemination? Results: Emergent patterns were detected when complex data structures were analyzed, which were not observed when variables were assessed individually. Complex properties–including data circularity–were demonstrated. The emergent patterns helped identify 11 counties as ‘disseminators’ or ‘facilitators’ (F) and 264 counties as ‘barriers’ (B) of epidemic spread. In the early epidemic phase, F and B counties differed in terms of road density and FMD case density. Focusing on non-biological, geographical data, a second analysis indicated that complex relationships may identify B-like counties even before epidemics occur. Discussion: Geographical barriers and/or promoters of disease dispersal may precede the introduction of emerging pathogens. If corroborated, the analysis of geo-referenced complexity may support anticipatory epidemiological policies.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Using Project Complexity Determinations to Establish Required Levels of Project Rigor

The concepts discussed in this paper 1) focus on using technical competencies and skills in making objective determinations regarding project complexity based on objective scoring criteria and 2) then using the complexity determinations to establish the level of rigor required in initiating, planning, executing, monitoring and controlling, and closing projects to maximize process efficiency. This paper presents a project complexity analysis methodology for defining the levels of project management process rigor a project team needs to employ to maximize project delivery efficiencies without compromising quality and performance. Methods for making project complexity determinations based on project lifecycle size, duration, organizational complexity, requirements, technology readiness, risk, and visibility are discussed. The paper correlates the levels of rigor needed by project management process groups given the determined level of project complexity. Next, the paper presents a graded approach to defining extent of team formation, planning documentation rigor, stakeholder communication rigor, requirements management rigor, acquisition planning, risk management, executing, and monitoring and controlling rigor dependent on project complexity determinations. Methods for integrating and aligning the project complexity determination methods into existing project management procedures and processes are also discussed as well as methods for training personnel in the use of the method and facilitating and monitoring effectiveness of implementation within an organization in which project delivery is a mission focus.

complexity, project, determination, management, tr↗
DOE OSTI2015

Syntheses, characterization and properties of silver, copper and palladium complexes from bis(oxazoline)-containing ligands

The reactions of 2,6-di(2-oxazolyl)pyridine (L{sup 1}) and 2,6-bis[(S)-4-phenyl-2-oxazolyl]pyridine (L{sup 2}) with silver, copper and palladium salts to yield six new complexes: ([Ag{sub 5}(L{sup 1}){sub 5}](BF{sub 4}){sub 5}){sub n} (1), ([Ag(L{sup 1})](SbF{sub 6})){sub n} (2), [Cu{sub 4}I{sub 4}(L{sup 1}){sub 2}] (3), [Cu{sub 6}I{sub 6}(L{sup 1}){sub 2}] (4), [Pd(L′{sup 1})(OAc)] (5), [Pd(L′{sup 2})Cl] (6), which were fully characterized by single-crystal and powder X-ray diffraction, IR, elemental and thermogravimetric analyses. 1 and 2 are a pair of Ag-oxazoline helical chain structure complexes. The spiral directions of chains are opposite in 1, while identical in 2; the measurement of CD spectra can further confirm their meso and chiral structures. Complexes 3 and 4 show eight-nuclear and twelve-nuclear iodine–cuprous cluster structure. Their structural diversity is induced by different molar ratios of CuI:L{sup 1}. Complexes 5 and 6 are discrete mononuclear palladium complexes. In situ oxazolyl-ring-opening reactions take place in the syntheses of them and the L{sup 1} and the L{sup 2} were transformed to their oxazolyl-ring opened derivatives L′{sup 1} and L′{sup 2}. Moreover, fluorescence, non-linear optical properties, and ferroelectric properties have been investigated. - Graphical abstract: 2,6-di(2-oxazolyl)pyridine (L{sup 1}) reacts with silver and copper salts to yield helical and cluster structure complexes. - Highlights: • Helical and cluster structure complexes. • In situ oxazolyl-ring-opening reactions. • Fluorescence, non-linear optical properties, and ferroelectric properties.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Phosphorescent Pt(II) and Pd(II) Complexes for Efficient, High-Color-Quality, and Stable OLEDs

Phosphorescent organic light-emitting diodes (OLEDs) are leading candidates for next-generation displays and solid-state lighting technologies. Much of the academic and commercial pursuits in phosphorescent OLEDs have been dominated by Ir(III) complexes. Over the past decade recent developments have enabled square planar Pt(II) and Pd(II) complexes to meet or exceed the performance of Ir complexes in many aspects. In particular, the development of N-heterocyclic carbene-based emitters and tetradentate cyclometalated Pt and Pd complexes have significantly improved the emission efficiency and reduced their radiative lifetimes making them competitive with the best reported Ir complexes. Furthermore, their unique and diverse molecular design possibilities have enabled exciting photophysical attributes including narrower emission spectra, excimer -based white emission, and thermally activated delayed fluorescence. These developments have enabled the fabrication of efficient and “pure” blue OLEDs, single-doped white devices with EQEs of over 25% and high CRI, and device operational lifetimes which show early promise that square planar metal complexes can be stable enough for commercialization. These accomplishments have brought Pt complexes to the forefront of academic research. The molecular design strategies, photophysical characteristics, and device performance resulting from the major advancements in emissive Pt and Pd square planar complexes are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Synthesis and Structure of Vanadium Halide Complexes Containing Diphosphine Ligands with Pendant Amines

A series of vanadium(III) diiodide complexes of the formula CpV(P R N R' P R )I 2 (Cp = 5-C 5 H 5 ; P R N R' P R = (R 2 PCH 2 ) 2 N(R)), where R = Et, R = Me (1a), R = Ph (1b); R = Ph, R = Me (1c)) is reported. The corresponding vanadium(II) monoiodide complexes of the formula CpV(P R N R' PR )I, where R = Et, R = Me (2a), R = Ph (2b); R = Ph, R = Me (2c)) were prepared in THF by reduction of 1a-c with Zn powder. The paramagnetic complexes 1a-c and 2a-c are characterized by elemental analysis, 1H NMR spectroscopy, and by cyclic voltammetry for complexes 2b and 4b. Complexes 1c and 2a-c were also characterized in the single crystal by X-ray crystallography. We report the preparation of the vanadium(II) complexes CpV(P Ph 2 N Ph 2 )I (3) (P Ph 2 N Ph 2 = 1,5-diphenyl-3,7-diphenyl-1,5-diaza-3,7-diphosphacyclooctane) and trans-[VCl 2 (PEtNMePEt)2] (4a) and trans-[VCl 2 (PEtNPhPEt) 2 ] (4b). These complexes represent initial coordination chemistry of vanadium complexes with P R N R' P R and P Ph 2 N Ph 2 diphosphine ligands, which contain a pendant amine in the second coordination sphere. This research was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Image quality and diagnostic accuracy of complex-averaged high b value images in diffusion-weighted MRI of prostate cancer

Purpose: To evaluate the impact of complex-averaging on image quality (IQ) and diagnostic accuracy of acquired and calculated high b value (aHBV, cHBV) images in diffusion-weighted prostate MRI. Materials and methods: This retrospective study included 84 patients who underwent multiparametric prostate MRI at 3 Tesla without endorectal coil. DWIs were acquired at three different b values which included two lower b values (b = 50,900 s/mm{sup 2}) and one higher b value (aHBV at 2000 s/mm{sup 2}). The acquired data were postprocessed to generate two different types of trace-weighted images—using conventional magnitude-averaging and complex-averaging. Using lower b values (b = 50,900 s/mm{sup 2}) from both conventional and complex-averaged image sets, cHBV images (b = 2000 s/mm{sup 2}) and ADC maps were derived. All image sets were reviewed by two radiologists in different reading sessions to assess image quality and PIRADS. The diagnostic accuracy of different image sets for the detection of prostate lesions was performed by correlating PIRADS and Gleason scores. Results: Complex-averaging did not impact ADC values of the prostate lesions compared to magnitude-averaging (P = 0.08). Complex-averaging improved image quality of acquired high b value and calculated high b value images (P < 0.0001). Complex-averaging also improved the level of confidence (LOC) of the acquired high b value for both readers (P < 0.0001, P < 0.05), but only for reader A in calculated high b value (P < 0.0001). The image quality of calculated high b value images was not significantly different than acquired high b value images. The dataset combining complex-averaging and calculated high b value provided the highest diagnostic accuracy (but not statistically significant) for detection of the significant prostate lesion compared to the magnitude-averaged acquired high b value (79.55% vs. 72.73%; P = 0.317). The mean acquisition time for b = 2000 s/mm{sup 2} sequence (aHBV) was 6 min 30 s (± 1 min 16 s) out of a total of 28 min 31 s (± 4 min 26 s) for the entire mp-MRI protocol (approximately 25% of total scan time). Conclusion: Complex-averaging provides better image quality and level of confidence without significant impact on ADC values and diagnostic accuracy for detection of the significant prostate lesions . The calculated high b value images are also comparable to (and can substitute) the acquired high b value images which can help in reducing the imaging time.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2017

Transition Metal (II) Complexes with a Novel Azo-azomethine Schiff Base Ligand: Synthesis, Structural and Spectroscopic Characterization, Thermal Properties and Biological Applications

The pyrimidine based azo-linked Schiff base ligand, 5-benzoyl-1-((E)-(2-hydroxy-3-methoxy-5-((E)phenyldiazenyl)benzylidene)amino)-4-phenylpyrimidin-2(1H)-one (HL), and its transition metal (II) complexes were synthesized and defined by using {sup 1}H-NMR, {sup 13}C-NMR, Elemental analysis, FT-IR, MS, UV–vis, molar conductance, magnetic susceptibility and thermal analysis techniques. According to the conductance data obtained indicate all of the metal complexes have non-electrolytic nature. Square pyramidal geometry for Pd(II) and octahedral geometry for all the other complexes synthesized was concluded from the electronic absorption spectra and magnetic susceptibility measurements of the complexes. Investigation of the significant infrared bands of the active groups in the ligand and the solid complexes alludes that HL is coordinated to the metal ions ONO tridentate manner. Moreover, the absorption and emission properties of the azo-azomethine based ligand and its complexes were investigated. The results obtained show that fluorescence emissions of the ligand and its metal (II) complexes depend on the type of transition metal ions and the derivatives displayed moderate Stokes’ shift values between 44 and 107 nm. All the compounds exhibited superb photostability. Further, antioxidant, antimicrobial and pBR322 plasmid DNA cleavage activities were investigated. All compounds showed good DPPH• (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity and complexes of [MnL{sub 2}]•H{sub 2}O and [NiL{sub 2}]•H{sub 2}O exhibited excellent metal chelating activity. All the compounds tested demonstrated two strand DNA cleavage activities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Spectroscopic, Computational, Antimicrobial, DNA Interaction, In Vitro Anticancer and Molecular Docking Properties of Biochemically Active Cu(II) and Zn(II) Complexes of Pyrimidine-Ligand

Biochemically active Cu(II) and Zn(II) complexes [CuL(ClO{sub 4}){sub 2}(1) and ZnL(ClO{sub 4}){sub 2}(2)] have been synthesized from N,N donor Schiff base ligand L derived from4,6-dichloropyrimdine-5-carboxaldehyde with 4-(2-aminoethyl)morpholine. The L, complexes 1 and 2 have been structurally characterized by elemental analysis, {sup 1}H-NMR, FTIR, MS, UV-Visible and ESR techniques. The results obtained from the spectral studies supports the complexes 1 and 2 are coordinated with L through square planar geometry. DFT calculations results supports, the ligand to metal charge transfer mechanism can occur between L and metal(II) ions. The antimicrobial efficacy results have been recommended that, complexes 1 and 2 are good anti-pathogenic agents than ligand L. The interaction of complexes 1 and 2 with calf thymus (CT) DNA has been studied by electronic absorption, viscometric, fluorometric and cyclic voltammetric measurements. The calculated K{sub b} values for L, complexes 1 and 2 found from absorption titrations was 4.45 × 10{sup 4}, L; 1.92 × 10{sup 5}, 1 and 1.65 × 10{sup 5}, 2. The Ksv values were found to be 3.0 × 10{sup 3}, 3.68 × 10{sup 3}and 3.52 × 10{sup 3} for L, complexes 1 and 2 by using competitive binding with ethidium bromide (EB). These results suggest that, the compounds are interacted with DNA may be electrostatic binding. The molecular docking studies have been carried out to confirm the interaction of compounds with DNA. Consequently, in vitro anticancer activities of L, complexes 1 and 2 against selected cancer (lung cancer A549, liver cancer HepG2 and cervical carcinoma HeLa) and normal (NHDF) cell lines were assessed by MTT assay.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2019

Chemically Modified Chitosan Bio-Sorbents for the Competitive Complexation of Heavy Metals Ions: A Potential Model for the Treatment of Wastewaters and Industrial Spills

Heavy metal pollution of water sources has become one of the most serious environmental and health problems nowadays. Chitosan (CHI) and derivatives can be used in the complexation and adsorption of heavy metals in water. Hence, this study compared the influence of CHI and carboxymethyl chitosan (CMC) ligands on the competitive complexation between toxic heavy metal ions with opposite charges Cr(VI) and Cd(II) at different pH values as an alternative and ecologically sustainable proposal for industrial spills of heavy metals into aquatic environments. The properties of the synthesized products and CHI were extensively characterized by several spectroscopy techniques, the competitive kinetics of complexation of metal ions with CHI and two type of CMC (with methanol, CMC 40-ME, and with ethanol, CMC 60-ET) was evaluated by wavelength dispersive X-ray fluorescence spectroscopy (WDXRF). The results clearly indicated the influence of the pH and ligands on the competitive complexation of the cationic or anionic ions. The results demonstrated that O-carboxymethylation of chitosan has occurred with a degree of functionalization of (1.20 ± 0.02) and (0.88 ± 0.02) for CMC 40-ME and CMC 60-ET, respectively, leading to the formation of CMC soluble in alkaline medium (pH range of 3.5 ≤ pH ≤ 6.5 and 4.0 ≤ pH ≤ 8.0 for CMC 40-ME and CMC 60-ET, respectively). In alkaline media, complexation of CMC 40-ME is approximately 10% higher (147.2 ± 0.9 mg g{sup −1}) than CMC 60-ET (99.8 ± 2.9 mg g{sup −1}) with Cd{sup 2+} ions at pH 8.5, and approximately 21% lower [(95 ± 2 mg g{sup −1}) and (96.3 ± 2.8 mg g{sup −1}) for CMC 40-ME and CMC 60-ET, respectively] than CHI (121 ± 6 mg g{sup −1}) for Cr{sub x}O{sub y}{sup z−} ions at pH 3.0. The kinetic analysis showed variations for each ion and a significant difference regarding the complexant towards the negatively charged ions. The CMC 40-ME, in any analyzed pH, the complexation occurred during the first 45 min of the process. These results showed that CMC, as polydentate functional ligand, was more efficient than CHI especially for the complexation of cations in basic media. Therefore, these systems appear to be attractive alternatives for the containment of industrial spills of heavy metals in wastewater.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2017

Analysis of Proteins, Protein Complexes, and Organellar Proteomes Using Sheathless Capillary Zone Electrophoresis - Native Mass Spectrometry

Native mass spectrometry (MS) is a rapidly advancing field in the analysis of proteins, protein complexes, and macromolecular species of various types. The majority of native MS experiments reported to-date has been conducted using direct infusion of purified analytes into a mass spectrometer. In this study, capillary zone electrophoresis (CZE) was coupled online to Orbitrap mass spectrometers using a commercial sheathless interface to enable high-performance separation, identification, and structural characterization of limited amounts of purified proteins and protein complexes, the latter with preserved non-covalent associations under native conditions. The performance of both bare-fused silica and polyacrylamide-coated capillaries was assessed using mixtures of protein standards known to form non-covalent protein–protein and protein–ligand complexes. High-efficiency separation of native complexes is demonstrated using both capillary types, while the polyacrylamide neutral-coated capillary showed better reproducibility and higher efficiency for more complex samples. The platform was then evaluated for the determination of monoclonal antibody aggregation and for analysis of proteomes of limited complexity using a ribosomal isolate from E. coli. Native CZE-MS, using accurate single stage and tandem-MS measurements, enabled identification of proteoforms and non-covalent complexes at femtomole levels. This study demonstrates that native CZE-MS can serve as an orthogonal and complementary technique to conventional native MS methodologies with the advantages of low sample consumption, minimal sample processing and losses, and high throughput and sensitivity. This study presents a novel platform for analysis of ribosomes and other macromolecular complexes and organelles, with the potential for discovery of novel structural features defining cellular phenotypes (e.g., specialized ribosomes). .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Complexity and near extremal charged black branes

Highlights: • Trying to explore a remedy to overcome the puzzle in holographic complexity by assuming a cutoff behind the horizon and the corresponding boundary term. • Holographic complexity growth obtained by the WDW patch on shell action is insensitive to the UV cutoff at the late time. Therefore one may conclude that either on shell action does not compute complexity, or the late time is not given by the physical charges, or in our computations we have missed something! • We find that one needs to carefully compute on shell action taking into account the behind the horizon and the corresponding boundary term. Doing so, one arrives at a consistent picture. • We check this consistency by evaluating the late time complexity growth for near horizon limit of the near extremal black hole using two different methods. We would have obtained non-consistent picture, if we had not considered the behind the horizon cutoff as well as the corresponding boundary term. We compute holographic complexity of charged black brane solutions in arbitrary dimensions for the near horizon limit of near extremal case using two different methods. The corresponding complexity may be obtained either by taking the limit from the complexity of the charged black brane, or by computing the complexity for near horizon limit of near extremal solution. One observes that these results coincide if one assumes to have a cutoff behind horizon whose value is fixed by UV cutoff and also taking into account a proper counterterm evaluated on this cutoff. We also consider the situation for Vaidya charged black branes too.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2017

Human alpha A-crystallin missing N-terminal domain poorly complexes with filensin and phakinin

Highlights: • In vitro complexes between αA, its deletion mutants with filensin and phakinin was determined. • Complexes were determined following ultracentrifugation and by electron microscopic methods. • N-terminal domain of αA-crystallin is needed to form complex with filensin and phakinin in vitro. The aim of this study was to determine relative importance of N-terminal domain and C-terminal extension of αA-crystallin during their in vitro complex formation with phakinin and filensin (the two lens-specific intermediate filament [IF] proteins). Cloned phakinin, filensin and vimentin were purified under a denaturing conditions by consecutive DEAE-cellulose-, hydroxyapatite- and Sephadex G-75-column chromatographic methods. WTαA-crystallin, αA-NT (N-terminal domain [residue number 1–63])-deleted and αA-CT (C-terminal terminal extension [residue number 140–173]-deleted), were cloned in pET 100 TOPO vector, expressed in BL-21 (DE3) cells using 1% IPTG, and purified using a Ni{sup 2+}-affinity column. The following two in vitro methods were used to determine complex formation of WT-αA, αA-NT, or αA-CT with phakinin, filensin or both phakinin plus filensin together: an ultracentrifugation sedimentation (centrifugation at 80,000 × g for 30 min at 20 °C) followed by SDS-PAGE analysis, and an electron microscopic analysis. In the first method, the individual control proteins (WT-αA, αA-NT and αA-CT crystallin species) remained in the supernatant fractions whereas phakinin, filensin, and vimentin were recovered in the pellet fractions. On complex formation by individual WT-αA-, αA-NT or αA-CT-species with filensin, phakinin or both phakinin and filensin, WT-αA and αA-CT were recovered in the pellet fraction with phakinin, filensin or both filensin and phakinin, whereas αA-NT remained mostly in the supernatant, suggesting its poor complex formation property. EM-studies showed filamentous structure formation between WT-αA and αA-CT with phakinin or filensin, or with both filensin and phakinin together but relatively poor filamentous structures with αA-NT. Together, the results suggest that the N-terminal domain of αA-crystallin is required during in vitro complex formation with filensin and phakinin.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2018

Electrocatalytic oxygen evolution with pure and substituted M 6 (SR) 12 (M=Pd, Fe, Rh) complexes

The development of new technologies to generate fuels from water splitting requires highly active and cost-effective catalysts. Organometallic complexes have attracted considerable interests due to their scientific significance and their ability to efficiently photo- and electro-catalyze H 2 and O 2 evolution reactions. Here, we combine density functional theory (DFT) and computational electrochemical analysis to predict the oxygen evolution reaction (OER) activity of a series of organometallic complexes containing methyl thiol ligands and compare it to that of Ni complex. Here, we find that the OER activity versus the diameter of the hexagonal ring shows a maximum activity which corresponds to that of Ni complex. We also find an existence of linear correlations of the adsorption energies with the ring diameter of the oxidized complexes. In an effort to improve the OER activity of these complexes, we substitute a metal cation with Ni, and we show that Ni-doped complexes give rise to smaller overpotentials. The enhanced overpotential can be explained in terms of the overall affinity of active sites for reactive species resulting in a shift of their binding energies. Finally, we find that substituting Fe atoms into small organometallic Ni complex does not appear to have the same influence that has been observed in bulk materials. We believe these predictions will help guide catalyst design by identifying active and robust OER catalysts, capable to reduce the energy required for the anodic water oxidation. Reducing anodic overpotentials will help reduce the overall energy requirements of both H 2 evolution and CO 2 reduction systems.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Step-by-step assembly of 4d-4f-3d complex based on heptamolybdate anion

Four new complexes, (NH{sub 4}){sub 11.9}[Ln{sub 4.7}(MoO{sub 4})(H{sub 2}O){sub 23}(Mo{sub 7}O{sub 24}){sub 4}]{center_dot}xH{sub 2}O (Ln=Pr, x=34 (1); Ln=Nd, x=19 (2)), [NH{sub 4}]{sub 28}[Ce{sub 8}(MoO{sub 4}){sub 2}(H{sub 2}O){sub 31}(Mo{sub 7}O{sub 24}){sub 8}]{center_dot}74H{sub 2}O (3), and (NH{sub 4}){sub 26}[CoPr{sub 8}(MoO{sub 4}){sub 2}(H{sub 2}O){sub 33}(Mo{sub 7}O{sub 24}){sub 8}]{center_dot}54H{sub 2}O (4) have been synthesized and characterized by single-crystal and powder X-ray diffraction, CHN elemental analyses TGA analyses, IR and UV-Vis spectroscopy. Complex 1-3 are 0D compounds constructed by the connection between Ln{sup III} ions and [Mo{sub 7}O{sub 24}]{sup 6-} unit. In complex 4, the existence of Co{sup II} connects the polyanion clusters into 1D chain. The introduction of 3d metal (cobalt cation) and 4f metal (Ln=Pr{sup III}, Nd{sup III}, Ce{sup III}) encourages the coordination capability for [Mo{sub 7}O{sub 24}]{sup 6-} unit, which shows interesting coordination modes. The [Mo{sub 7}O{sub 24}]{sup 6-} unit in 1-4 shows three new coordination modes, connecting up to four metal cations. Complexes 1-4 show antiferromagnetic behavior via variable temperature magnetic study. The photoluminescence spectrum indicates the photoluminescence property for 4. - Graphical abstract: Heptamolybdate anion shows extraordinary coordination geometry in the presence of both lanthanide cation (Pr{sup III}) and transitional metal cation (Co{sup II}), which give rise to a new 4d-4f-3d complex. Black-Small-Square Highlights: Black-Right-Pointing-Pointer A new 4d-4f-3d complex that containing 1D chain was obtained and discussed. Black-Right-Pointing-Pointer New coordination geometry with higher coordination number of heptamolybdate. Black-Right-Pointing-Pointer Series of heptamolybdate contained complexes were synthesized and characterized. Black-Right-Pointing-Pointer Complexes mentioned above show antiferromagnetic behavior.

36 MATERIALS SCIENCE↗
DOE OSTI2025

f-Element complexes with benzyl and cyclohexyl substituted trihydroborates

Actinide complexes containing the simplest borohydrides (BH 4 ) 1- and (MeBH 3 ) 1- can exhibit remarkably highly volatility, which creates unique hazards and handling challenges, especially when making measurements on solid samples under vacuum. Here we describe efforts to prepare new actinide borohydride complexes with attenuated volatility by adding bulkier benzyl (Bn) and cyclohexyl (Cy) substituents to boron. Reactions of ThCl 4 , UI 3 (thf) 4 , and NdI 3 with the mixed alkali metal salt Li/K(BnBH 3 )(thf) n yielded Th(BnBH 3 ) 4 (thf) 2 , U(BnBH 3 ) 4 (thf) 2 , and K[Nd(BnBH 3 ) 4 ], respectively. Notable amongst these, the reaction with UI 3 (thf) 4 proceeds via oxidation of U(III) to U(IV) despite the presence of reducing borohydride ligands. Similarly, reactions of the same metal halides with four equivalents of Li(CyBH 3 )(Et 2 O) n yielded Th(CyBH 3 ) 4 , U(CyBH 3 ) 4 (thf) 2 , and [Li(Et 2 O) 3 ][Nd(CyBH 3 ) 4 ]. Single crystal X-ray diffraction studies of the M(BnBH 3 ) 4 (thf) 2 complexes with M = Th and U confirmed their formulations. Furthermore, the complexes have approximate D 2d point group symmetry and adopt bicapped hexagonal antiprismatic coordination geometries with axial thf ligands and κ 3 -BnBH 3 ligands bound in the equatorial plane. K[Nd(BnBH 3 ) 4 ] and [Li(Et 2 O) 3 ][Nd(CyBH 3 ) 4 ], which were prepared for comparison to U(III) complexes that were unsuccessfully targeted, were also structurally characterized to reveal complex anions with tetrahedral arrangements of trihydroborate ligands bound to Nd(III). Crystals obtained for Th(CyBH 3 ) 4 and U(CyBH 3 ) 4 (thf) 2 were not suitable for XRD studies, but 1 H and 11 B NMR spectra were consistent with their formulations. Collectively, these complexes represent rare examples of structurally characterized f-element trihydroborate complexes with carbon substituents other than methyl.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Phase Behavior and Salt Partitioning in Polyelectrolyte Complex Coacervates

Polyelectrolyte complexes are omnipresent both in nature and in the technological world, including nucleotide condensates, biological marine adhesives, food stabilizers, encapsulants, and carriers for gene therapy. However, the true phase behavior of complexes, resulting from associative phase separation of oppositely charged polyelectrolytes, remains poorly understood. Here in this study, we rely on complementary experimental and simulation approaches to create a complete quantitative description of the phase behavior of polyelectrolyte complexes that represents a significant advance in our understanding of the underlying physics of polyelectrolyte complexation. Experiments employing multiple approaches with model polyelectrolytes oppositely charged polypeptides poly(L-lysine) and poly(D,Lglutamic acid) of matched chain lengths led to phase diagrams with compositions of the complex and the supernatant that were in excellent agreement with simulation results. Contrary to the widely accepted theory for complexation, we found preferential partitioning of salt ions into the supernatant phase. Additionally, the salt partitioning into the supernatant phase was found to initially increase and then decrease on increasing the salt concentrations, manifesting as a distinct minimum in the salt partition coefficients. These trends were shown by simulations to be strongly influenced by the excluded volume interactions in the complex phase, which were not accounted for in their entirety in earlier theories. Finally, we believe the comprehensive data we present will be conducive to the development of an accurate physical theory for polyelectrolyte complexation with predictive capabilities.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Thermodynamic Trends for Reduction of CO by Molecular Complexes

Selective reduction of CO 2 into fuels and chemical feedstocks is highly desirable to reduce our dependence on fossil fuels. Most molecular catalysts afford 2e – reduction products, such as CO or HCO 2 – , as opposed to more reduced products. Here we present an analysis of the thermodynamic limitations for reduction of the CO ligand in the form of a series of isostructural group 6 carbonyl complexes, Cp*M(CO) 3 (P(OMe) 3 ) + (M = Cr, Mo, and W). Additionally, the free energy for stepwise transfer of a hydride (H – ) and a proton (H + ) to the CO ligand, resulting in a hydroxycarbene (CHOH) complex, was measured by equilibration with H – /H + donors and acceptors with known hydricity or acidity. Together, these two reaction steps are equivalent to a net addition of H 2 across the CO ligand. A large and unfavorable free energy for H 2 addition (Δ G ° H2 ) was measured for all three complexes and decreases in the order Cr > Mo > W. The trend for these complexes is opposite to the trend previously reported for group 7 carbonyl complexes, for which Δ G ° H2 decreases moving up the group, Re > Mn. Computational analysis indicates the trends can be described in terms of electrostatic effects, where a low Δ G ° H2 is obtained in complexes that balance the atomic charges of the M–C≡O fragment of the complex. These findings can be used to design metal carbonyl complexes with a more energetically accessible H 2 addition, which will facilitate the development of molecular catalysts for reduction of CO.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗