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DOE OSTI2015

Low-dimensional compounds containing cyanido groups. XXVIII. Crystal structure, spectroscopic and magnetic properties of two copper(II) tetracyanidoplatinate complexes with 1,2-diaminopropane

Violet crystals of ([Cu(pn){sub 2}]{sub 2}[Pt(CN){sub 4}])[Pt(CN){sub 4}]·2H{sub 2}O (1, pn=1,2-diaminopropane) and blue crystals of [Cu(pn)Pt(CN){sub 4}]{sub n}·nH{sub 2}O (2) were prepared under hydrothermal conditions and characterized using elemental analysis, IR and UV–vis spectroscopy and by X-ray crystal structure analysis. Different number of ν(C≡N) absorption bands of these two compounds reflects their different structures. An X-ray crystal structure analysis has shown that complex 1 is of ionic character and is formed from trinuclear [Cu(pn){sub 2}–Pt(CN){sub 4}–Cu(pn){sub 2}]{sup 2+} complex cation and discrete [Pt(CN){sub 4}]{sup 2–} anion together with two molecules of crystal water. On the other hand, complex 2 is of polymeric character and is formed by 2D networks of [Cu(pn)Pt(CN){sub 4}]{sub n} composition and completed by n molecules of crystal water. Magnetic measurements show the presence of a weak antiferromagnetic exchange interaction in complex 1 (Θ=–0.2 K), while the magnetic susceptibility of complex 2 is well described by the model of uniform S=1/2 spin chain with exchange interaction J/k{sub B}=–1.64 K. - Graphical abstract: Two complexes of different structural types from the system Cu(II) – 1,2–diaminopropane – [Pt(CN){sub 4}]{sup 2–} have been isolated. These were characterized by IR and UV–VIS spectroscopy, X–ray crystal structure analysis together with the magnetic measurements. On one hand ([Cu(pn){sub 2}]{sub 2}[Pt(CN){sub 4}])[Pt(CN){sub 4}]∙2H{sub 2}O is of ionic character and is formed from trinuclear complex cation and discrete anion together with two molecules of crystal water. On the other hand, [Cu(pn)Pt(CN){sub 4}]{sub n}∙nH{sub 2}O is of polymeric character and is formed by 2D networks of [Cu(pn)Pt(CN){sub 4}]{sub n} composition and completed by n molecules of crystal water. - Highlights: • Two complexes of different compositions from one system have been isolated. • First complex is of ionic character and second one is of polymeric character. • Polymeric complex described as a spin chain in contrast to its bilayer structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2015

Assembly and property research on seven 0D–3D complexes derived from imidazole dicarboxylate and 1,2-bi(pyridin-4-yl)ethene

The hydrothermal reaction of transition metals, 1H-imidazole-4,5-dicarboxylic acid (H{sub 3}ImDC) and 1,2-bi(pyridin-4-yl)ethene (bpe) affords a series of new complexes, namely, [Mn(HImDC)(bpe)(H{sub 2}O)] (1), [M(H{sub 2}ImDC){sub 2}(H{sub 2}O){sub 2}]·(bpe) (M=Fe(2), Co(3), Zn(4), Cd(6)), [Zn{sub 3}(ImDC){sub 2}(bpe)(H{sub 2}O)]·3H{sub 2}O (5) and [Cd(H{sub 2}ImDC)(bpe)] (7), which are characterized by elemental analyses, IR, TG, XRPD and single crystal X-ray diffraction. Complex 1 exhibits a one dimensional (1D) zigzag chain with two types of irregular rings, and the 1D chains are linked to form a three dimensional (3D) supramolecular framework by the hydrogen bonding interactions (O–H∙∙∙O and O–H∙∙∙N). Complexes 2–4 and 6 are isomorphous, and they display the mononuclear structures. In these complexes, the O–H∙∙∙O and O–H∙∙∙N hydrogen bonds play an important role in sustaining the whole 3D supramolecular frameworks. Complex 5 shows a (3,3)-connected 3D framework with (10{sup 3}) topology, and the lattice water molecules as guest molecules exist in the 3D framework. Complex 7 is a wave-like two dimensional (2D) structure, in which the adjacent 1D chains point at the opposite directions. Moreover, the fluorescent properties of complexes 1–7 and the magnetic property of 1 have been investigated. The water vapor adsorption for complex 5 has been researched at 298 K. - Graphical abstract: Seven new complexes based on different structural characteristics have been hydrothermally synthesized by the mixed ligands. The fluorescent properties, the magnetic property and the water vapor adsorption have been investigated. - Highlights: • The semi-rigid ligand with C=C bonds and imidazole dicarboxylates with some advantages have been used. • A series of new complexes with different structural characteristics have been discussed in detail. • The fluorescent properties, the magnetic property and the water vapor adsorption have been investigated.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Effects of Non-Electrostatic Intermolecular Interactions on the Phase Behavior of pH-Sensitive Polyelectrolyte Complexes

Polyelectrolyte complexes (PECs) offer enormous material tunability and desirable functionalities, and consequently have found broad utility in biomedical and material industries. While poly(acrylic acid) (PAA) and poly( allylamine hydrochloride) (PAH) are a commonly used pairing, various aspects of the phase behavior of PAA-PAH complexes have not been sufficiently quantified. In this work, we present a comprehensive experimental study depicting the binodal phase boundaries for the PAA-PAH complexes prepared under acidic, neutral, and basic conditions using thermogravimetric analysis, turbidimetry, and optical microscopy. Under neutral and basic conditions, phase behaviors of the complexes were largely similar to one another and followed general expectations of PEC phase behavior, except for unusually high resistance to disruption of the complex with added salt. Stable complexes are observed up to 4 M NaCl concentrations. Under acidic conditions, strikingly different phase behaviors of the PAA-PAH complexes were observed. The polymer content in the complex phase increased initially, followed by an expected decrease as salt was added to the complexes. This behavior may result from a combination of associative phase separation of PAA and PAH chains, influenced by electrostatic interactions, and segregative phase separation, which can be ascribed to the influence of a combination of the hydrophobic interactions of the aliphatic polymer backbone and the interpolymer hydrogen bonding of unionized acrylic monomer units. Our systematic investigations over a range of pH detailing these discrepancies in the PAA-PAH phase behavior are expected to clarify the inconsistencies among the reports in the literature and provide the material design strategies for practical use of the PAA-PAH complexes and multilayer assemblies.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2023

Luminescent Bimetallic Two-Coordinate Gold(I) Complexes Utilizing Janus Carbenes

A series of bimetallic carbene-metal-amide (cMa) complexes have been prepared with bridging biscarbene ligands to serve as a model for the design of luminescent materials with large oscillator strengths and small energy differences between the singlet and triplet states (ΔE ST ). The complexes have a general structure (R 2 N)Au(:carbene—carbene:)Au(NR 2 ). The bimetallic complexes show solvation-dependent absorption and emission that is analyzed in detail. It is found that the molar absorptivity of the bimetallic complexes is correlated with the energy barrier to rotation of the metal–ligand bond. The bimetallic cMa complexes also exhibit short emission lifetimes (τ = 200–300 ns) with high photoluminescence efficiencies (Φ PL > 95%). The radiative rates of bimetallic cMa complexes are 3–4 times faster than that of the corresponding monometallic complexes. Analysis of temperature-dependent luminescence data indicates that the lifetime for the singlet state (τS 1 ) of bimetallic cMa complexes is near 12 ns with a ΔE ST of 40–50 meV. Here the presented compounds provide a general design for cMa complexes to achieve small values for ΔE ST while retaining high radiative rates. Solution-processed organic light-emitting devices (OLEDs) made using two of the complexes as luminescent dopants show high efficiency and low roll-off at high luminance.

14 SOLAR ENERGY↗

DOE OSTI2024

Single-Molecule Detection of the Encounter and Productive Electron Transfer Complexes of a Photosynthetic Reaction Center

Small, diffusible redox proteins play an essential role in electron transfer (ET) in respiration and photosynthesis, sustaining life on Earth by shuttling electrons between membrane-bound complexes via finely tuned and reversible interactions. Ensemble kinetic studies show transient ET complexes form in two distinct stages: an “encounter” complex largely mediated by electrostatic interactions, which subsequently, through subtle reorganization of the binding interface, forms a “productive” ET complex stabilized by additional hydrophobic interactions around the redox-active cofactors. Here, using single-molecule force spectroscopy (SMFS) we dissected the transient ET complexes formed between the photosynthetic reaction center-light harvesting complex 1 (RC-LH1) of Rhodobacter sphaeroides and its native electron donor cytochrome c 2 (cyt c 2 ). Importantly, SMFS resolves the distribution of interaction forces into low (~150 pN) and high (~330 pN) components, with the former more susceptible to salt concentration and to alteration of key charged residues on the RC. Thus, the low force component is suggested to reflect the contribution of electrostatic interactions in forming the initial encounter complex, whereas the high force component reflects the additional stabilization provided by hydrophobic interactions to the productive ET complex. Employing molecular dynamics simulations, we resolve five intermediate states that comprise the encounter, productive ET and leaving complexes, predicting a weak interaction between cyt c 2 and the LH1 ring near the RC-L subunit that could lie along the exit path for oxidized cyt c 2 . The multimodal nature of the interactions of ET complexes captured here may have wider implications for ET in all domains of life.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2025

Isolation of Inner-Sphere Aquo Complexes of Samarium(II)

The cis-anti-cis and cis-syn-cis isomers of [Sm(dicyclohexano-18-crown-6)(H 2 O) 2 ]I 2 exhibiting trans water molecules bound to the Sm 2+ ion have been isolated and characterized. Sm 2+ possesses an electrochemical potential sufficient for water reduction, and thus these complexes add to the recent body of evidence that the oxidation of Sm 2+ by water can operate by a mechanism that is not straightforward. These complexes are obtained by the direct addition of stoichiometric amounts of water to solutions of the respective Sm(dicyclohexano-18-crown-6)I 2 isomers under an inert atmosphere. The parent complex, Sm(dicyclohexano-18-crown-6)I 2 , lacking coordinating water molecules can be obtained through rigorous exclusion of water. It was determined that the bulky cyclohexano-substituents deter intramolecular interactions between [Sm(dicyclohexano-18-crown-6)(H 2 O) 2 ]I 2 complexes and slow the oxidization of the metal centers. The extent of the stability of these complexes to the presence of water has been further probed through cyclic voltammetry, where it was found that the redox potential of both isomers of [Sm(dicyclohexano-18-crown-6)(H 2 O) 2 ]I 2 maintains quasi-reversible behavior with a 50,000-fold excess of water to Sm 2+ in solution with the cis-syn-cis complex being quasi-reversible at even higher concentrations of water. Solution-phase spectroscopy of these complexes in acetonitrile shows a corresponding hypsochromic shift of the Sm 2+ 4f → 5d transition typically observed in the visible region from Sm 2+ complexes. Here, the crystalline compounds obtained in this study support solid-state spectroscopic trends observed from other Sm 2+ crown-ether complexes containing iodide counterions, wherein the proximity of the iodide ions to the metal center determines whether the complex can exhibit 4f → 4f photoluminescence.

Crystals↗

DOE OSTI2024

Insights into coordination and ligand trends of lanthanide complexes from the Cambridge Structural Database

Abstract Understanding lanthanide coordination chemistry can help develop new ligands for more efficient separation of lanthanides for critical materials needs. The Cambridge Structural Database (CSD) contains tens of thousands of single crystal structures of lanthanide complexes that can serve as a training ground for both fundamental chemical insights and future machine learning and generative artificial intelligence models. This work aims to understand the currently available structures of lanthanide complexes in CSD by analyzing the coordination shell, donor types, and ligand types, from the perspective of rare-earth element (REE) separations. We obtain four sets of lanthanide complexes from CSD: Subset 1, all Ln-containing complexes (49472 structures); Subset 2, mononuclear Ln complexes (27858 structures); Subset 3, mononuclear Ln complexes without cyclopentadienyl ligands (Cp) (26156 structures); Subset 4, Ln complexes with at least one 1,10-phenanthroline (phen) or its derivative as a coordinating ligand (2226 structures). The subsequent analysis of lanthanide complexes in these subsets examines the trends in coordination numbers and first shell distances as well as identifies and characterizes the ligands and donor groups. In addition, examples of Ln-complexes with commercially available complexants and phen-based ligands are interrogated in detail. This systematic investigation lays the groundwork for future data-driven ligand designs for REE separations based on the structural insights into the lanthanide coordination chemistry.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2017

Benzoquinonoid-bridged dinuclear actinide complexes

We report here the coordination chemistry of the tripodal tris[2-amido(2-pyridyl)ethyl]amine ligand, L, with thorium(IV) and uranium(IV). Using a salt-metathesis strategy from the potassium salt of this ligand, K 3 L, new actinide complexes were isolated, namely the dimeric thorium complex [ThCl(L)] 2 (1) and the monomeric uranium complex UI(THF)(L) (2); under different crystallisation conditions, the dimeric uranium complex is also isolated, [UI(L)] 2 (2-dimer). With the aim of studying electronic phenomena such as magnetic exchange between two actinide ions, we have synthesised the first examples of dinuclear, quinoid-bridged actinide complexes from dianionic 2,5-bis[2,6-(diisopropyl)anilide]-1,4-benzoquinone (Q Dipp ) and 2,5-bis[2-(methoxy)anilide]-1,4-benzoquinone (Q OMe ) ligands. The resulting complexes are [Th(L)] 2 Q Dipp (3), [Th(THF)(L)] 2 Q OMe (5) and [U(L)] 2 Q OMe (6). The targeted [U(L)] 2 Q Dipp complex (4) could not be isolated. All isolated complexes have been characterised by spectroscopic methods and X-ray crystallography. The uranium(IV) complexes 2-dimer and 6 have been studied by SQUID magnetometry but indicate that there is negligible magnetic exchange between the two uranium(IV) ions. The reduced form of 6, [K(18-c-6)][6 - ] is unstable and highly sensitive, but X-ray crystallography indicates that it is a novel U IV U IV complex bridged by a quinoid-radical.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2016

DFT study of small fullerene dimer complexes C{sub 20}-N{sub m}@C{sub n} (m = 1-6 and n = 24, 28, 32, 36 and 40)

First principle calculations based on density functional theory were performed to calculate the structural and electronic properties of C{sub 20}-N{sub m}@C{sub n} dimer complexes. The calculated binding energies of the complexes formed are comparable to C{sub 60} dimer which ensures their stability. The bond lengths of these dimer complexes were found to be nearly same as pure complexes C{sub 20}-C{sub n}. Further, nitrogen (N) atoms were encapsulated inside the secondary cage (C{sub n}) of dimer complexes and the number of N atoms depends on diameter of the cage. The HOMO-LUMO gaps of new proposed complexes indicate the increase in gap as compared to pure complexes. Mulliken charge analysis of these complexes has been studied which shows the significant charge transfer from the N atoms to the secondary cage of these complexes. The study propose the formation of the new dimer complexes which are stable and are able to encapsulate atoms which are otherwise reactive in free space.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2015

SU-E-T-418: Explore the Sensitive of the Planar Quality Assurance to the MLC Error with Different Beam Complexity in Intensity-Modulate Radiation Therapy

Purpose: The purpose of this study is to investigate the sensitivity of the planar quality assurance to MLC errors with different beam complexities in intensity-modulate radiation therapy. Methods: sixteen patients’ planar quality assurance (QA) plans in our institution were enrolled in this study, including 10 dynamic MLC (DMLC) IMRT plans measured by Portal Dosimetry and 6 static MLC (SMLC) IMRT plans measured by Mapcheck. The gamma pass rate was calculated using vender’s software. The field numbers were 74 and 40 for DMLC and SMLC, respectively. A random error was generated and introduced to these fields. The modified gamma pass rate was calculated by comparing the original measured fluence and modified fields’ fluence. A decreasing gamma pass rate was acquired using the original gamma pass rate minus the modified gamma pass rate. Eight complexity scores were calculated in MATLAB based on the fluence and MLC sequence of these fields. The complexity scores include fractal dimension, monitor unit of field, modulation index, fluence map complexity, weighted average of field area, weighted average of field perimeter, and small aperture ratio ( <5cm{sup 2} and <50cm{sup 2}). The Spearman’s rank correlation coefficient was implemented to analyze the correlation between these scores and decreasing gamma rate. Results: The relation between the decreasing gamma pass rate and field complexity was insignificant for most complexity scores. The most significant complexity score was fluence map complexity for SMLC, which have ρ =0.4274 (p-value=0.0063). For DMLC, the most significant complex score was fractal dimension, which have ρ=−0.3068 (p-value=0.0081). Conclusions: According to the primarily Result of this study, the sensitivity gamma pass rate was not strongly relate to the field complexity.

60 APPLIED LIFE SCIENCES↗

DOE OSTI2022

SAXS analysis of the intrinsic tenase complex bound to a lipid nanodisc highlights intermolecular contacts between factors VIIIa/IXa

Abstract The intrinsic tenase (Xase) complex, formed by factors (f) VIIIa and fIXa, forms on activated platelet surfaces and catalyzes the activation of factor X to Xa, stimulating thrombin production in the blood coagulation cascade. The structural organization of the membrane-bound Xase complex remains largely unknown, hindering our understanding of the structural underpinnings that guide Xase complex assembly. Here, we aimed to characterize the Xase complex bound to a lipid nanodisc with biolayer interferometry (BLI), Michaelis–Menten kinetics, and small-angle X-ray scattering (SAXS). Using immobilized lipid nanodiscs, we measured binding rates and nanomolar affinities for fVIIIa, fIXa, and the Xase complex. Enzyme kinetic measurements demonstrated the assembly of an active enzyme complex in the presence of lipid nanodiscs. An ab initio molecular envelope of the nanodisc-bound Xase complex allowed us to computationally model fVIIIa and fIXa docked onto a flexible lipid membrane and identify protein–protein interactions. Our results highlight multiple points of contact between fVIIIa and fIXa, including a novel interaction with fIXa at the fVIIIa A1–A3 domain interface. Lastly, we identified hemophilia A/B-related mutations with varying severities at the fVIIIa/fIXa interface that may regulate Xase complex assembly. Together, our results support the use of SAXS as an emergent tool to investigate the membrane-bound Xase complex and illustrate how mutations at the fVIIIa/fIXa dimer interface may disrupt or stabilize the activated enzyme complex.

Hematology↗

DOE OSTI2023

Follistatin Forms a Stable Complex With Inhibin A That Does Not Interfere With Activin A Antagonism

Abstract Inhibins are transforming growth factor-β family heterodimers that suppress follicle-stimulating hormone (FSH) secretion by antagonizing activin class ligands. Inhibins share a common β chain with activin ligands. Follistatin is another activin antagonist, known to bind the common β chain of both activins and inhibins. In this study, we characterized the antagonist-antagonist complex of inhibin A and follistatin to determine if their interaction impacted activin A antagonism. We isolated the inhibin A:follistatin 288 complex, showing that it forms in a 1:1 stoichiometric ratio, different from previously reported homodimeric ligand:follistatin complexes, which bind in a 1:2 ratio. Small angle X-ray scattering coupled with modeling provided a low-resolution structure of inhibin A in complex with follistatin 288. Inhibin binds follistatin via the shared activin β chain, leaving the α chain free and flexible. The inhibin A:follistatin 288 complex was also shown to bind heparin with lower affinity than follistatin 288 alone or in complex with activin A. Characterizing the inhibin A:follistatin 288 complex in an activin-responsive luciferase assay and by surface plasmon resonance indicated that the inhibitor complex readily dissociated upon binding type II receptor activin receptor type IIb, allowing both antagonists to inhibit activin signaling. Additionally, injection of the complex in ovariectomized female mice did not alter inhibin A suppression of FSH. Taken together, this study shows that while follistatin binds to inhibin A with a substochiometric ratio relative to the activin homodimer, the complex can dissociate readily, allowing both proteins to effectively antagonize activin signaling.

Endocrinology & Metabolism↗

DOE OSTI2012

A Case for Sandia Investment in Complex Adaptive Systems Science and Technology

This white paper makes a case for Sandia National Laboratories investments in complex adaptive systems science and technology (S&T) -- investments that could enable higher-value-added and more-robustly-engineered solutions to challenges of importance to Sandia's national security mission and to the nation. Complex adaptive systems are ubiquitous in Sandia's national security mission areas. We often ignore the adaptive complexity of these systems by narrowing our 'aperture of concern' to systems or subsystems with a limited range of function exposed to a limited range of environments over limited periods of time. But by widening our aperture of concern we could increase our impact considerably. To do so, the science and technology of complex adaptive systems must mature considerably. Despite an explosion of interest outside of Sandia, however, that science and technology is still in its youth. What has been missing is contact with real (rather than model) systems and real domain-area detail. With its center-of-gravity as an engineering laboratory, Sandia's has made considerable progress applying existing science and technology to real complex adaptive systems. It has focused much less, however, on advancing the science and technology itself. But its close contact with real systems and real domain-area detail represents a powerful strength with which to help complex adaptive systems science and technology mature. Sandia is thus both a prime beneficiary of, as well as potentially a prime contributor to, complex adaptive systems science and technology. Building a productive program in complex adaptive systems science and technology at Sandia will not be trivial, but a credible path can be envisioned: in the short run, continue to apply existing science and technology to real domain-area complex adaptive systems; in the medium run, jump-start the creation of new science and technology capability through Sandia's Laboratory Directed Research and Development program; and in the long run, inculcate an awareness at the Department of Energy of the importance of supporting complex adaptive systems science through its Office of Science.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗

DOE OSTI2023

Ab Initio Calculations on the Ground and Excited Electronic States of Thorium–Ammonia, Thorium–Aza-Crown, and Thorium–Crown Ether Complexes

Positively charged metal–ammonia complexes are known to host peripheral, diffuse electrons around their molecular skeleton. The resulting neutral species form materials known as expanded or liquid metals. Alkali, alkaline earth, and transition metals have been investigated previously in experimental and theoretical studies of both the gas and condensed phase. This work is the first ab initio exploration of an f-block metal–ammonia complex. The ground and excited states are calculated for Th0–3+ complexes with ammonia, crown ethers, and aza-crown ethers. For Th3+ complexes, the one valence electron Th populates the metal’s 6d or 7f orbitals. For Th0–2+, the additional electrons prefer occupation of the outer s- and p-type orbitals of the complex, except Th(NH3)10, which uniquely places all four electrons in outer orbitals of the complex. Although thorium coordinates up to ten ammonia ligands, octa-coordinated complexes are more stable. Crown ether complexes have a similar electronic spectrum to ammonia complexes, but excitations of electrons in the outer orbitals of the complex are higher in energy. Aza-crown ethers disfavor the orbitals perpendicular to the crowns, attributed to the N-H bonds pointing along the plane of the crowns.

74 ATOMIC AND MOLECULAR PHYSICS↗

DOE OSTI2022

Manganese(II) complexes of 1,1'-bis[(pyridin-2-yl)methyl)]-2,2'-bipiperidine (PYBP): Synthesis, structure, catalytic properties in alkene epoxidation with hydrogen peroxide, and related mechanistic studies

In this study, several manganese(II) complexes with the stereoisomers of ligand PYBP (1,1'-bis[(pyridin-2-yl)methyl]-2,2'-bipiperidine) and different anions were prepared and characterized by X-ray diffractometry. Complex [Mn II (rac-PYBP)] 2+ (1) was found to be an efficient catalyst of alkene epoxidation by hydrogen peroxide in the presence of acetic acid in acetonitrile at room temperature. Cyclooctene was converted to its epoxide with up to 91 % yield, 99.6 % selectivity, and the turnover number of 180 within 5 min. Fast epoxidations of cyclohexene, 1-decene, styrene, and cis-stilbene were also achieved. Isomeric complex [Mn II (meso-PYBP)] 2+ (2) was catalytically inactive under the same experimental conditions. Stopped-flow spectrophotometry and freeze-quenched EPR spectra show that complex 2 is not oxidized by H 2 O 2 in the presence of acetic acid (AcOH) but instead undergoes partial ligand protonation and liberation of the Mn 2+ cations due to the relatively poor chelating ability of ligand meso-PYBP. The rac-PYBP isomer acts as a better ligand and retains the coordinated Mn center when complex 1 is treated with the H 2 O 2 /AcOH mixture in acetonitrile solution yielding a mixture of intensely colored intermediates likely involving Mn III , Mn IV , and Mn V complexes. Magnetic susceptibility measurements, UV–vis and EPR spectra suggest that dinuclear complexes [Mn III 2 (μ-O)(μ-OAc)(rac-PYBP) 2 ] 3+ and [Mn III Mn IV (μ-O) 2 (rac-PYBP) 2 ] 3+ gradually accumulate in the reaction mixture as inactivated states of the catalyst. Complex 1 also causes fast decomposition of hydrogen peroxide into O 2 gas and H 2 O, which competes with the epoxidation of alkenes and requires gradual addition of H 2 O 2 for its efficient use. The catalytic activity of complex 1 is strongly influenced by its counterions and decreases in order ClO 4 - ≈ SbF 6 - > NO 3 – > Cl - indicating that labile ligands in the coordination sphere of Mn are required for the activation of H 2 O 2 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Synthesis, structures and properties of a series of manganese coordination complexes constructed from dicarboxylic fluorene derivatives

Assembly reactions of 9,9-diethylfluorene-2,7-dicarboxylic acid (H{sub 2}DFDC) and Mn(CH{sub 3}COO){sub 2}{center_dot}4H{sub 2}O or MnCl{sub 2}{center_dot}4H{sub 2}O by tuning of various secondary ligands such as 2,2 Prime -bipyridine (2,2 Prime -bpy), 4,4 Prime -bipyridine (4,4 Prime -bpy) or 1,3-bis(4-pyridyl)propane) (bpp), gave rise to four complexes {l_brace} [Mn{sub 2}(DFDC){sub 2}(DMF){sub 2}]{center_dot}H{sub 2}O{r_brace} {sub n} (1), [Mn(DFDC)(2,2 Prime -bpy)]{sub n} (2), {l_brace} [Mn{sub 2}(DFDC){sub 2}(4,4 Prime -bpy){sub 2}]{center_dot}2CH{sub 3}OH{r_brace} {sub n} (3), and {l_brace} [Mn{sub 4}(DFDC){sub 4}(bpp){sub 2}(CH{sub 3}OH){sub 3} (H{sub 2}O){sub 3}]{center_dot}3(CH{sub 3}OH){center_dot}3(H{sub 2}O){r_brace} {sub n} (4). Single crystal X-ray diffraction analysis reveal that complex 1 is three dimensional structure with rhombic channels filled by guest water molecules; 2 presents a close-packed structure with high thermal stability; 3 exhibits a three dimensional framework with micro-porous channels filled by guest methanol molecules and 4 is a two-dimensional structure. The photoluminescent properties of 1-4 have been studied, respectively, showing that the Mn(II) ions, accessorial organic ligands or crystal structures exert important influences on the photoluminescence emissions of H{sub 2}DFDC ligands. Thermogravimetric analysis show that the complexes have remarkably high thermal stability. Magnetic susceptibility measurements have been finished and discussed for the complexes. - Graphical abstract: Assembly of 9,9-diethylfluorene-2,7-dicarboxylic acid and Mn(II) salts by tuning of various accessorial ligands resulted in four manganese complexes with different topological frameworks. Highlights: Black-Right-Pointing-Pointer Four manganese complexes based on 9,9-diethylfluorene-2,7-dicarboxylic acid were obtained. Black-Right-Pointing-Pointer The complexes were structurally characterized by single-crystal X-ray diffraction. Black-Right-Pointing-Pointer The complexes 1-4 display different topological structures. Black-Right-Pointing-Pointer Thermogravimetric analysis show the complexes have remarkably high thermal stability.

36 MATERIALS SCIENCE↗

DOE OSTI2023

Double Intramolecular 1,2 C–H Addition of o -Methyl Groups To Form Ruthenium Pincer Double Tuck-In Complexes

Ruthenium pincer complexes have a rich history of coordination and reaction chemistries. In this work, we report our discoveries of previously unreported Ru pincer coordination geometries. We found that mono tuck-in κ 4 -ArPN H PRuLCl complexes react with NaN(SiMe 3 ) 2 producing double tuck-in mer-κ 5 -ArPN H PRuL complexes. Interestingly, when κ 4 -MesPN H PRuCl is dehydrohalogenated, the resulting double tuck-in complex binds N 2 , forming the nitrogen complex κ 5 -MesPN H PRuN 2 . Further, the mer-κ 5 -ArPN H PRuL complexes thermally isomerize to the fac-κ 5 -ArPN H PRuL isomers, which is an uncommon reaction for pincer complexes. The mer-κ 5 -ArPN H PRuL complexes react with CO and CO 2 to form amide κ 4 -ArPN H PRu(CO)L or carbamate κ 5 -ArPN(CO 2 )PRuL complexes, respectively, supporting the hypothesis that the κ 4 -ArPNPRuL amide intermediates are accessible and reactive.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2013

Thermodynamic Features of Benzene-1,2-Diphosphonic Acid Complexes with Several Metal Ions

Among his many contributions to the advancement of f-element chemistry and separation science, Professor Gregory R. Choppin’s research group completed numerous investigations featuring the application of distribution techniques to the determination of metal complexation equilibrium quotients. Most of these studies focused on the chemistry of lanthanide and actinide complexes. In keeping with that tradition, this report discusses the complex formation equilibrium constants for complexes of trivalent europium (Eu3+) with benzene-1,2-diphosphonic acid (H4BzDP) determined using solvent extraction distribution experiments in 0.2 M (Na,H)ClO4 media in the temperature range of 5 – 45 degrees C. Protonation constants for HnBzDP4-n and stoichiometry and stability of BzDP4- complexes with Zn2+, Ni2+, and Cu2+ have also been determined using potentiometric titration (at I = 0.1 M) and 31P NMR spectroscopy. Heats of protonation of HnBzDPn-4 species have been determined by titration calorimetry. From the temperature dependence of the complex Eu3+-HnBzDPn-4 equilibrium constant, a composite enthalpy (?H = -15.1 (+/-1.0) kJ mol-1) of complexation has been computed. Comparing these thermodynamic parameters with literature reports on other diphosphonic acids and structurally similar carboxylic acids indicates that exothermic heats of complexation are unique to the Eu-BzDP system. Comparisons with thermodynamic data from the literature indicate that the fixed geometry imposed by the benzene ring enhances complex stability.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗