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All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Electronic structure and reactivity studies of a nonsymmetric one-electron oxidized Cu II bis-phenoxide complex

Here, the tetradentate mixed imino/amino phenoxide ligand (N-(3,5-di- tert -butylsalicylidene)-N'-(2-hydroxyl-3,5-di-tert-butylbenzyl))- trans -1,2-cyclohexanediamine (salalen) was complexed with Cu II , and the resulting Cu complex (2) was characterized by a number of experimental techniques and theoretical calculations. Two quasi-reversible redox processes for 2, as observed by cyclic voltammetry, demonstrated the potential stability of oxidized forms, and also the increased electron-donating ability of the salalen ligand in comparison to the salen analogue. The electronic structure of the one-electron oxidized [2] + was studied in detail, and Cu K-edge X-ray Absorption Spectroscopy (XAS) measurements confirmed a Cu II -phenoxyl radical complex in solution. Resonance Raman (rR) and variable temperature 1 H NMR studies, coupled with theoretical calculations, showed that [2 • ] + is a triplet (S = 1) Cu II -phenoxyl radical species, with localization of the radical on the more electron-rich aminophenoxide. Attempted isolation of X-ray quality crystals of [2 • ] + afforded [2H] + , with a protonated phenol bonded to Cu II , and an additional H-bonding interaction with the SbF 6 – counterion. Stoichiometric reaction of dilute solutions of [2 • ] + with benzyl alcohol showed that the complex reacts in a similar manner as the oxidized Cu II -salen analogue, and does not exhibit a substrate-binding pre-equilibrium as observed for the oxidized bis-aminophenoxide Cu II -salan derivative.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Modern Palliative Radiation Treatment: Do Complexity and Workload Contribute to Medical Errors?

Purpose: To examine whether treatment workload and complexity associated with palliative radiation therapy contribute to medical errors. Methods and Materials: In the setting of a large academic health sciences center, patient scheduling and record and verification systems were used to identify patients starting radiation therapy. All records of radiation treatment courses delivered during a 3-month period were retrieved and divided into radical and palliative intent. 'Same day consultation, planning and treatment' was used as a proxy for workload and 'previous treatment' and 'multiple sites' as surrogates for complexity. In addition, all planning and treatment discrepancies (errors and 'near-misses') recorded during the same time frame were reviewed and analyzed. Results: There were 365 new patients treated with 485 courses of palliative radiation therapy. Of those patients, 128 (35%) were same-day consultation, simulation, and treatment patients; 166 (45%) patients had previous treatment; and 94 (26%) patients had treatment to multiple sites. Four near-misses and 4 errors occurred during the audit period, giving an error per course rate of 0.82%. In comparison, there were 10 near-misses and 5 errors associated with 1100 courses of radical treatment during the audit period. This translated into an error rate of 0.45% per course. An association was found between workload and complexity and increased palliative therapy error rates. Conclusions: Increased complexity and workload may have an impact on palliative radiation treatment discrepancies. This information may help guide the necessary recommendations for process improvement for patients who require palliative radiation therapy.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2025

A conserved chaperone protein is required for the formation of a noncanonical type VI secretion system spike tip complex

Type VI secretion systems (T6SSs) are dynamic protein nanomachines found in Gram-negative bacteria that deliver toxic effector proteins into target cells in a contact-dependent manner. Prior to secretion, many T6SS effector proteins require chaperones and/or accessory proteins for proper loading onto the structural components of the T6SS apparatus. However, despite their established importance, the precise molecular function of several T6SS accessory protein families remains unclear. In this study, we set out to characterize the DUF2169 family of T6SS accessory proteins. Using gene co-occurrence analyses, we find that DUF2169-encoding genes strictly co-occur with genes encoding T6SS spike complexes formed by valine-glycine repeat protein G (VgrG) and DUF4150 domains. Although structurally similar to Pro-Ala-Ala-Arg (PAAR) domains, “PAAR-like” DUF4150 domains lack PAAR motifs and instead contain a conserved PIPY motif, leading us to designate them PIPY domains. Next, we present both genetic and biochemical evidence that PIPY domains require a cognate DUF2169 protein to form a functional T6SS spike complex with VgrG. This contrasts with canonical PAAR proteins, which bind VgrG on their own to form functional spike complexes. By solving the first crystal structure of a DUF2169 protein, we show that this T6SS accessory protein adopts a novel protein fold. Furthermore, biophysical and structural modeling data suggest that DUF2169 contains a dynamic loop that physically interacts with a hydrophobic patch on the surface of its cognate PIPY domain. Based on these findings, we propose a model whereby DUF2169 proteins function as molecular chaperones that maintain VgrG–PIPY spike complexes in a secretion-competent state prior to their export by the T6SS apparatus.

DUF2169↗
DOE OSTI2017

An efficient hybrid technique in RCS predictions of complex targets at high frequencies

Most computer codes in Radar Cross Section (RCS) prediction use Physical Optics (PO) and Physical theory of Diffraction (PTD) combined with Geometrical Optics (GO) and Geometrical Theory of Diffraction (GTD). The latter approaches are computationally cheaper and much more accurate for curved surfaces, but not applicable for the computation of the RCS of all surfaces of a complex object due to the presence of caustic problems in the analysis of concave surfaces or flat surfaces in the far field. The main contribution of this paper is the development of a hybrid method based on a new combination of two asymptotic techniques: GTD and PO, considering the advantages and avoiding the disadvantages of each of them. A very efficient and accurate method to analyze the RCS of complex structures at high frequencies is obtained with the new combination. The proposed new method has been validated comparing RCS results obtained for some simple cases using the proposed approach and RCS using the rigorous technique of Method of Moments (MoM). Some complex cases have been examined at high frequencies contrasting the results with PO. This study shows the accuracy and the efficiency of the hybrid method and its suitability for the computation of the RCS at really large and complex targets at high frequencies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2018

Formulation and computation of dynamic, interface-compatible Whitney complexes in three dimensions

A discrete De Rham complex enables compatible, structure-preserving discretizations for a broad range of partial differential equations problems. Such discretizations can correctly reproduce the physics of interface problems, provided the grid conforms to the interface. However, large deformations, complex geometries, and evolving interfaces makes generation of such grids difficult. We develop and demonstrate two formally equivalent approaches that, for a given background mesh, dynamically construct an interface-conforming discrete De Rham complex. Both approaches start by dividing cut elements into interface-conforming subelements but differ in how they build the finite element basis on these subelements. The first approach discards the existing non-conforming basis of the parent element and replaces it by a dynamic set of degrees of freedom of the same kind. The second approach defines the interface-conforming degrees of freedom on the subelements as superpositions of the basis functions of the parent element. These approaches generalize the Conformal Decomposition Finite Element Method (CDFEM) and the extended finite element method with algebraic constraints (XFEM-AC), respectively, across the De Rham complex.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2011

The complex synthesis and solid state chemistry of ceria-lanthana solid solutions prepared via a hexamethylenetetramine precipitation

Mixed oxide solid solutions are becoming ever more commercially important across a range of applications. However, their synthesis can be problematical. Here, we show that ceria-lanthana solid solutions can be readily prepared via simple precipitation using hexamethylenetetramine. However, the solution chemistry can be complex, which results in the precipitated particles having a complex structure and morphology. Great care must be taken in both the synthesis and characterisation to quantify the complexity of the product. Even very high heat treatments were not able to produce highly homogeneous materials and X-ray diffractions reveals the non-equilibrium form of particles prepared in this way. Unexpected crystal structures are revealed including a new metastable cubic La{sub 2}O{sub 3} phase. - Graphical abstract: The suggested mechanism for the formation of dual fluorite phase particles, where Step 1 corresponds to room temperature aging, Step 2; heating the solution to 90 deg. C, Step 3; cooling of the solution to room temperature, Step 4; calcination to 500 deg. C, Step 5; calcination to 700 deg. C and Step 6; calcination to 1300 deg. C. The terminology of e.g. La{sub 1-x}Ce{sub x}(OH){sub 3} is used to indicate the formation of a mixed oxy-hydroxy participate rather than a definitive assignment of stoichiometry. Similarly, La{sub 1-y}Ce{sub y}O{sub 2} only implies a mixed solid solution. Highlights: > Mol% of prepared Ce-La oxides did not follow that of reactant mol%. > Complex reaction pathway found to be dependent on metal solution concentrations. > At certain concentrations core shell particles were found to form. > A reaction model was produced based on cationic solubility. > Report lanthana solubility higher than previously reported in CeO{sub 2}.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

Small non-polar complexes exhibiting significant piezoelectric properties: Solvothermal synthesis and crystal structures of MO{sub 5}V(tren){center_dot}H{sub 2}O (M=Mo and W; tren=tris(2-aminoethyl)amine)

The two isostructural complexes MO{sub 5}V(tren){center_dot}H{sub 2}O (M=Mo (1) and W (2)) were synthesized under solvothermal conditions at pH Almost-Equal-To 12 crystallizing in the non-centrosymmetric space group P2{sub 1}2{sub 1}2{sub 1}. The structures are constructed by a distorted tetrahedral [MO{sub 4}]{sup 2-} anion bound via one shared oxygen atom to a severely distorted [V{sup IV}N{sub 4}O]{sup 2+} complex completing the octahedral coordination around the V centre. The two O atoms in the VN{sub 4}O{sub 2} octahedron are in cis position. The two compounds represent rare examples where the [MO{sub 4}]{sup 2-} anion is acting as a ligand. Both compounds exhibit a piezoelectric effect which is more pronounced for M=Mo. The samples are further characterized with IR and UV/Vis spectroscopy and thermal analysis. - Graphical abstract: The complexes [(V(tren)O)(MO4)]{center_dot}H2O (M = Mo, W; tren = tris(2-aminoethyl)amine)) composed of vertex-linked [MO4]{sup 2-} tetrahedron and [VN4O6]{sup 2+}octahedron. Highlights: Black-Right-Pointing-Pointer [MO{sub 4}]{sup 2-} tetrahedron (M=Mo, W) acting as ligand. Black-Right-Pointing-Pointer Jahn-Teller and steric distortion of the [VN{sub 4}O{sub 2}]{sup 2+} octahedron. Black-Right-Pointing-Pointer Non-centrosymmetric complexes exhibiting pronounced piezoelectric effect.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2012

A 3D complex containing novel 2D Cu{sup II}-azido layers: Structure, magnetic properties and effects of 'Non-innocent' reagent

A novel copper-azido coordination polymer, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (1, HL=pyrazine-2-carboxylic acid), has been synthesized by hydrothermal reaction with 'Non-innocent' reagent in the aqueous solution. In the reaction system, Cu{sup II} ions are avoided to reduce to Cu{sup I} ions due to the existence of Nd{sup III}. It is found that the complex is a 3D structure based on two double EO azido bridged trimmers and octahedron Cu{sup II} ions, in which the azide ligands take on EO and {mu}{sub 1,1,3} mode to form Cu{sup II}-azido 2D layers, furthermore L ligands pillar 2D layers into an infinite 3D framework with the Schlaefli symbol of {l_brace}4;6{sup 2}{r_brace}4{l_brace}4{sup 2};6{sup 12};8{sup 10};10{sup 4}{r_brace}{l_brace}4{sup 2};6{sup 4}{r_brace}. Magnetic studies revealed that the interactions between the Cu{sup II} ions in the trimmer are ferromagnetic for the Cu-N-Cu angle nearly 98 Degree-Sign , while the interactions between the trimmer and octahedron Cu{sup II} ion are antiferromgantic and result in an antiferromagnetic state. - Graphical abstract: A 3D complex containing novel 2D Cu{sup II}-azido layers, [Cu{sub 2}(N{sub 3}){sub 3}(L)]{sub n} (HL=pyrazine-2-carboxylic acid), was synthesized by hydrothermal reaction and exhibit interesting structure and magnetic properties. Highlights: Black-Right-Pointing-Pointer 'Non-innocent' reagents plays a key role in the process of formation of this complex. Black-Right-Pointing-Pointer 2D layer is formed only by Cu{sup II} ions and azido ligands. Black-Right-Pointing-Pointer Pyrazine-2-carboxylate ligands reinforce 2D layers and pillar them into an infinite 3D framework. Black-Right-Pointing-Pointer Magnetic study indicates that alternating FM-AF coupling exists in the complex.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

Two molecular wheels 12-MC-6 complexes: Synthesis, structure and magnetic property of [Co(μ{sub 2}-SEt){sub 2}]{sub 6} and [Fe(μ{sub 2}-SEt){sub 2}]{sub 6}

The syntheses and structures of two ethyl mercaptan molecular wheels complexes, [M(μ{sub 2}-SCH{sub 2}CH{sub 3}){sub 2}]{sub 6} (M=Fe, Co), have been reported. Each metal atom is surrounded by four S atoms of the μ{sub 2}-SCH{sub 2}CH{sub 3} ligands in a distorted square plane fashion. The edge-sharing S{sub 4} square planes connect with each other to form a ring. Six metal atoms are located at the vertices of an almost hexagon, with M···M separations in the range of 2.903(1)∼2.936(2) Å for Fe and 2.889(2)∼2.962(2) Å for Co. The diameter of the ring, defined as the average distance between two opposing metal atoms, is 5.850(1) Å for Fe and 5.780(1) Å for Co, respectively. The magnetic property behaves of cobalt(II) cluster complex is studied. Highlights: • Two new ethyl mercaptan cyclic hexanuclear complexes were reported. • The crystal structures shown center formation of M{sub 6}S{sub 12} molecular wheels. • The Co{sub 6} ring cluster complex represents as weak ferromagnet.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Temperature evolution of nickel sulphide phases from thiourea complex and their exchange bias effect

Considering the very complex phase diagram of nickel sulphide, it is quite challenging to stabilize pure phases from a single precursor. Here, we obtain nanoparticles of various phases of nickel sulphide by decomposing nickel–thiourea complex at different temperatures. The first phase in the evolution is the one with the maximum sulphur content, namely, NiS{sub 2} nanoparticles obtained at 400 °C. As the temperature is increased, nanoparticles of phases with lesser sulphur content, NiS (600 °C) and Ni{sub 3}S{sub 2} (800 °C) are formed. NiS{sub 2} nanoparticles exhibit weak ferromagnetic transition at 30 K and show a large exchange bias at 2 K. NiS nanoparticles are antiferromagnetic and show relatively smaller exchange bias effect. On the other hand, Ni{sub 3}S{sub 2} nanoparticles exhibit very weak temperature dependent magnetization. Electrical measurements show that both NiS{sub 2} and NiS are semiconductors whereas Ni{sub 3}S{sub 2} is a metal. - Graphical abstract: Pure phases of NiS{sub 2}, NiS and Ni{sub 3}S{sub 2} have been obtained by thermal decomposition of nickel–thiourea complex wherein, NiS{sub 2} nanoparticles exhibit remarkable exchange bias effect at 2 K. - Highlights: • NiS{sub 2}, NiS and Ni{sub 3}S{sub 2} nanoparticles are obtained by thermal decomposition of nickel–thiourea complex at different temperatures. • As the temperature is increased, nickel sulphide phase with lesser sulphur content is obtained. • NiS{sub 2} nanoparticles show good exchange bias property which can be explained by antiferromagnetic core and ferromagnetic shell model. • NiS{sub 2} and NiS are semiconducting while Ni{sub 3}S{sub 2} shows metallic behavior.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Synthesis and characterization of a 1D chain-like Cu{sub 6} substituted sandwich-type phosphotungstate with pendant dinuclear Cu–azido complexes

A novel Cu–azido complex modified hexa-Cu{sup II} substituted sandwich-type phosphotungstate [Cu(en){sub 2}]([Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}])·6H{sub 2}O (1) (en=ethylene-diamine) has been prepared under hydrothermal conditions and structurally characterized by elemental analyses, IR spectra, powder X-ray diffraction (PXRD) and single-crystal X-ray diffraction. 1 displays a beautiful 1-D chain architecture constructed from sandwich-type [Cu{sub 2}(en){sub 2}(μ-1,1-N{sub 3}){sub 2}(H{sub 2}O)]{sub 2}[Cu{sub 6}(en){sub 2}(H{sub 2}O){sub 2}(B-α-PW{sub 9}O{sub 34}){sub 2}]{sup 2−} units and [Cu(en){sub 2}]{sup 2+} linkers. To our knowledge, 1 represents the first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes. - Graphical abstract: The first hexa-Cu{sup II} sandwiched phosphotungstate with supporting Cu–azido complexes has been prepared and characterized. Display Omitted - Highlights: • Hexa-copper-substituted phosphotungstate. • Cu–azido complexes modified hexa-Cu{sup II} substituted sandwich-type polyoxometalate. • 1-D chain architecture built by hexa-copper-substituted polyoxotungstate units.

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

Novel bipyridinyl oxadiazole-based metal coordination complexes: High efficient and green synthesis of 3,4-dihydropyrimidin-2(1H)-ones through the Biginelli reactions

Three new metal coordination complexes, namely, [Co(BPO){sub 2}(H{sub 2}O){sub 4}](BS){sub 2}(H{sub 2}O){sub 2} (1), [Co(BPO){sub 2}(H{sub 2}O){sub 4}](ABS){sub 2}(H{sub 2}O){sub 2} (2), [Co(BPO){sub 2}(H{sub 2}O){sub 4}](MBS){sub 2}(H{sub 2}O){sub 2} (3) [BPO=2,5-di(pyridin-4-yl)-1,3,4-oxadiazole, BS=benzenesulphonate, ABS=4-aminobenzenesulphonate, MBS=4-methylbenzenesulphonate] were obtained under hydrothermal conditions. Complexes 1–3 were structurally characterized by single-crystal X-ray diffraction, powder X-ray diffraction, IR and thermogravimetric analyses (TGA). All of them display a zero-dimensional motif, in which strong intermolecular hydrogen bonding interactions (O–H···O/N) and packing interactions (C–H···π and π···π) make them achieve a three-dimensional supramolecular architecture. The primary catalytic results of these three complexes show that high efficiency for the green synthesis of a variety of 3,4-dihydropyrimidin-2(1H)-ones was observed under solvent free conditions through Biginelli reactions. The present catalytic protocols exhibit advantages such as excellent yield, easy isolation, eco-friendly conditions, and short reaction time. - Graphical abstract: Three new metal coordination complexes with bipyridinyl-oxadiazole were obtained under hydrothermal conditions, which display a zero-dimensional motif, and show high efficiency for the green synthesis of a variety of 3,4-dihydropyrimidin-2(1H)-ones under solvent free conditions through Biginelli reactions. The present catalytic protocols exhibit advantages such as excellent yield, easy isolation, eco-friendly conditions, and short reaction time. Display Omitted.

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

Photon optimizer (PO) vs progressive resolution optimizer (PRO): a conformality- and complexity-based comparison for intensity-modulated arc therapy plans

This study aimed to provide guidance on the advantages and limitations of a new optimizer, “photon optimizer” (PO), when compared with its predecessor, “progressive resolution optimizer” (PRO), for intensity-modulated arc therapy (IMAT) plans. Eleven study plans that included a cohort of prostate, head and neck, and brain treatment sites were optimized using both PRO and PO algorithms. A plan template using the same objectives for the same number of iterations was used for each optimized plan to obtain hypothetical treatment plans that would be comparable with a clinical plan. Analysis was performed using plan conformity-based parameters such as target volume coverage factor, conformation number and homogeneity indices, and plan complexity assessment parameters such as small aperture score, modulation indices, and monitor unit variation with arc angle for prostate, brain and head, and neck IMAT treatment plans. Plan conformality analysis demonstrated that conformation numbers, target volume coverage factors, and homogeneity indices produced by the 2 optimizers were comparable for most anatomic sites. IMAT treatment plans produced using the PRO optimizer were found to be less complex than plans produced using the PO optimizer, in terms of multileaf collimator (MLC) leaf position variability and modulation complexity scores. Similarly, the PRO optimizer was shown to produce treatment plans that used fewer monitor units (and generally fewer monitor unit per degree of arc rotation) than PO optimizer. This study demonstrated that the PO optimizer can produce IMAT treatment plans with a similar degree of dose conformity to the target volume and generally improved organ at risk sparing, compared with the PRO optimizer. Better coverage to organs at risk produced by plans optimized using PO was observed to have higher MLC variability and monitor units. Therefore, careful evaluation of treatment plan conformity and complexity before assessing its deliverability is recommended when implementing the routine use of PO optimizer.

61 RADIATION PROTECTION AND DOSIMETRY↗
DOE OSTI2018

A trithiol bifunctional chelate for 72,77 As: A matched pair theranostic complex with high in vivo stability

Trithiol chelates are suitable for labeling radioarsenic ( 72 As: 2.49 MeV β + , 26 h; 77 As: 0.683 MeV β - , 38.8 h) to form potential theranostic radiopharmaceuticals for PET imaging and therapy. In this paper, to investigate the in vivo stability of trithiol chelates complexed with no carrier added (nca) radioarsenic, a bifunctional trithiol chelate was developed, and conjugated to bombesin(7–14)NH 2 as a model peptide. A trithiol-BBN(7–14)NH 2 bioconjugate and its arsenic complex were synthesized and characterized. The trithiol-BBN(7–14)NH 2 conjugate was radiolabeled with 77 As, its in vitro stability assessed, and biodistribution studies were performed in CF-1 normal mice of free [ 77 As]arsenate and 77 As-trithiol- BBN(7–14)NH 2 . The trithiol-BBN(7–14)NH 2 conjugate, its precursors and its As-trithiol-BBN(7–14)NH 2 complex were fully characterized. Radiolabeling studies with nca 77 As resulted in over 90% radiochemical yield of 77 As-trithiol-BBN, which was stable for over 48 h. Biodistribution studies were performed with both free [ 77 As]arsenate and Sep-Pak® purified 77 As-trithiol-BBN(7–14)NH 2 . Compared to the fast renal clearance of free [ 77 As]arsenate, 77 As-trithiol-BBN(7–14)NH 2 demonstrated increased retention with clearance mainly through the hepatobiliary system, consistent with the lipophilicity of the 77 As-trithiol-BBN(714)NH 2 complex. Finally, the combined in vitro stability of 77 As-trithiol-BBN(7–14)NH 2 and the biodistribution results demonstrate its high in vivo stability, making the trithiol a promising platform for developing radioarsenic-based theranostic radiopharmaceuticals.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2017

Iron speciation in peats: Chemical and spectroscopic evidence for the co-occurrence of ferric and ferrous iron in organic complexes and mineral precipitates

The speciation of iron (Fe) in organic matter (OM)-rich environments under in situ variable redox conditions is largely unresolved. Peatlands provide a natural setting to study Fe–OM interactions. Utilizing chemical, spectroscopic and theoretical modeling approaches, we report the chemical forms, oxidation states and local coordination environment of naturally occurring Fe in the vertically redox-stratified Manning peatlands of western New York. In addition, we report dominant carbon, sulfur and nitrogen species that can potentially stabilize the various Fe species present in these peatlands. Our results provide clear direct and indirect evidence for the co-occurrence of ferrous (Fe 2+ ) and ferric (Fe 3+ ) iron species in peats under both oxic and anoxic conditions. Iron is mostly present within the operationally defined organic and amorphous (i.e., short range ordered, SRO) fractions; ferric iron primarily as magnetically isolated paramagnetic Fe 3+ in Fe(III)-organic complexes, but also in mineral forms such as ferrihydrite; ferrous iron in tetrahedral coordination in Fe(II)-organic complexes with minor contribution from pyrite. All of the Fe species identified stabilize Fe(III) and/or Fe(II) in anoxic and oxic peats. Fundamental differences are also observed in the relative proportion of C, S and N functionalities of OM in oxic and anoxic peats. Aromatic C=C, ester, phenol and anomeric C (R-O-C-O-R), as well as thiol, sulfide and heterocyclic N functionalities are more prevalent in anoxic peats. Collectively, our experimental evidence suggests iron forms coordination complexes with O-, S- and N-containing functional groups of OM. We posit the co-occurrence of organic and mineral forms of Fe(II) and Fe(III) in both oxic and anoxic peat layers results from dynamic complexation and hydrolysis-precipitation reactions that occur under variable redox conditions. In conclusion, our findings aid in understanding the crucial role OM plays in determining Fe species in soils and sediments.

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

Aryl-substituted BIAN complexes of iron dibromide: Synthesis, X-ray and electronic structure, and catalytic hydrosilylation activity

Anhydrous iron dibromide complexes bearing bidentate a-diimine ligands ArN@C(Me)A(Me)C@NAr and ArBIAN (BIAN = bis(imino)acenaphthene; Ar = dpp and Mes; dpp = 2,6-diisopropylphenyl; Mes = 2,4,6-trimethylphenyl) have been prepared and characterized by 1H NMR spectroscopy. The aryl-substituted BIAN complexes were structurally characterized by single-crystal X-ray diffraction, and their metrical parameters are consistent with a redox-innocent chelating ligand. A high-spin iron(II) electronic structure description for the ArBIAN iron complexes is supported by Mössbauer spectroscopy, solution state magnetic measurements, and quantum-chemical calculations. Upon reduction, the iron complexes promote catalytic hydrosilylation of 1-hexene with phenylsilane at 22 _C. Under optimized conditions, 1 mol% of the dppBIANFeBr2 precatalyst was activated in situ to produce 1-hexylphenylsilane in high yield from a 1:1 ratio of 1-hexene:PhSiH3 in solvent-free conditions at 22 _C in 24 h.

Supej, Michael J.↗
DOE OSTI2023

A series of four-coordinate heteroleptic copper(I) complexes with diimine and β-diketiminate ligands

In this paper, a series of heteroleptic bis-chelate copper(I) complexes of the general formula Cu(N^N)(NacNac R ), where N^N is the diimine ligand and NacNac R is the β-diketiminate ligand are introduced. The complexes are easily prepared by reacting NacNac ligands with CuO t Bu in the presence of diimine ligands. The molecular structures of all complexes are characterized by NMR spectroscopy and X-ray crystallography. The studies of cyclic voltammetry and UV–vis absorption spectra show that the HOMO and the LUMO energy level can be tailored by changing the substitution pattern of each ligand. The oxidation potential is dependent on the NacNac ligand, and the reduction potential shows the dependence on the diimine ligand. In conclusion, tunable redox potentials and a wide range of visible absorption can make these copper(I) complexes promising candidates for applications in solar light harvesting.

14 SOLAR ENERGY↗
DOE OSTI2023

Synthesis and characterization of the actinide tosylimido complexes [K(18-crown-6)][An(NSO 2 -$p$-tolyl)(NR 2 ) 3 ] (An = U, Th; R = SiMe 3 )

Reaction of 1 equiv of KN(H)Ts (Ts = p-MeC 6 H 4 SO 2 ) with the actinide metallacycles, [An IV (CH 2 SiMe 2 NSiMe 3 )(NR 2 ) 2 ] (An = U, Th; R = SiMe 3 ), in the presence of 18-crown-6, affords the imido complexes, [K(18-crown-6)][An IV (NTs)(NR 2 ) 3 ] (An = U, 1; Th, 2), in modest to moderate yields after work-up. Both complexes were characterized by X-ray crystallography and 1 H and 13 C{ 1 H} NMR spectroscopies. To our knowledge, they represent the first sulfonylimido complexes reported for the f elements. Finally, they are also a rare example of an isostructural set of actinide imido complexes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗