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Results for “structural complexity”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,099 records · Page 61
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

An integrated approach for structural characterization of complex solid state electrolytes: the case of lithium lanthanum titanate

For neutron scattering and first principles simulation we integrate them to reveal the atomic-level to nanoscale structure of lithium lanthanum titanate (LLTO), a representative solid electrolyte material with applications in Li-ion batteries. Furthermore, the integrated approach solves the hierarchical local structure of LLTO in detail, including the coupled chemical order and topological distortion, as well as their correlation length scale and the spatial modulation with coherent boundaries. Ab initio molecular dynamics simulations are used to map out the distribution of the mobile ions and identify the migration pathway. This integrated approach provides a powerful means for detailed study of materials with complex local chemical and topological environment.

25 ENERGY STORAGE↗
DOE OSTI2015

Blue light emission from cyclometallated iridium (III) cyano complexes: Syntheses, crystal structures, and photophysical properties

In this study, we describe the synthesis and crystal structures of four iridium compounds containing the 2-(4,6-difluorophenyl)pyridyl ligand. Cleavage of dichloro-bridged iridium(III) dimers with phosphorus ligands leads to (46dfppy)2Ir(L)(Cl) where L = PPh 3 or P(OPh) 3 . Treatment of the chloro compounds with cyanide forms the cyano complexes (46dfppy) 2 Ir(L)(CN). All complexes exhibit a trans effect in their molecular structures due to the phosphorus ligands, with the phosphite having a greater effect than the phosphine. With L = PPh 3 , blue photoluminescence with CIE coordinates (x = 0.16, y = 0.24), quantum yield of 0.66 ± 0.15 and 4.5 ± 0.5 μs decay time is measured. For L = P(OPh) 3 , blue photoluminescence with CIE coordinates (x = 0.16, y = 0.21), quantum yield of 0.65 ± 0.15 and 2.9 ± 0.3 μs decay time is measured.

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

Structure of Methanol Solvated Iodozinc(II) Complexes in Solution

The structures of the solvated zinc ion and the solvated zinc–iodide complexes in methanol solution have been determined by EXAFS. The zinc ion is six-coordinated in an octahedral fashion with a mean Zn–O bond distance of 2.071(4) Å . According to the stability constants of the zinc–iodide system in methanol solution the first complex, ZnI + , is suppressed, which may indicate that a coordination change takes place at this step. On the other hand, the second complex, ZnI 2 , predominates at excess of iodide. The methanol solvated ZnI 2 complex has a tetrahedral structure with mean Zn–I and Zn–O bond distances of 2.55(1) and 1.99(1) Å , respectively. The mean Zn–I bond distance in a solution containing a maximal content of ZnI + , ca. 12%, strongly indicates that the first complex also has a tetrahedral structure.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Structure of the antenna complex expressed during far-red light photoacclimation in Synechococcus sp. PCC 7335

Far-red light photoacclimation, or FaRLiP, is a facultative response exhibited by some cyanobacteria that allows them to absorb and utilize lower energy light (700–800 nm) than the wavelengths typically used for oxygenic photosynthesis (400–700 nm). During this process, three essential components of the photosynthetic apparatus are altered: photosystem I, photosystem II, and the phycobilisome. In all three cases, at least some of the chromophores found in these pigment–protein complexes are replaced by chromophores that have red-shifted absorbance relative to the analogous complexes produced in visible light. Recent structural and spectroscopic studies have elucidated important features of the two photosystems when altered to absorb and utilize far-red light, but much less is understood about the modified phycobiliproteins made during FaRLiP. We used single-particle, cryo-EM to determine the molecular structure of a phycobiliprotein core complex comprising allophycocyanin variants that absorb far-red light during FaRLiP in the marine cyanobacterium Synechococcus sp. PCC 7335. The structure reveals the arrangement of the numerous red-shifted allophycocyanin variants and the probable locations of the chromophores that serve as the terminal emitters in this complex. It also suggests how energy is transferred to the photosystem II complexes produced during FaRLiP. The structure additionally allows comparisons with other previously studied allophycocyanins to gain insights into how phycocyanobilin chromophores can be tuned to absorb far-red light. These studies provide new insights into how far-red light is harvested and utilized during FaRLiP, a widespread cyanobacterial photoacclimation mechanism.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2015

Clinical Candidate VT-1161's Antiparasitic EffectIn Vitro, Activity in a Murine Model of Chagas Disease, and Structural Characterization in Complex with the Target Enzyme CYP51 from Trypanosoma cruzi

A novel antifungal drug candidate, the 1-tetrazole-based agent VT-1161 [(R)-2-(2,4-difluorophenyl)-1,1-difluoro-3-(1H-tetrazol-1-yl)-1-{5-[4-(2,2,2-trifluoroethoxy)phenyl]pyridin-2-yl}propan-2-ol], which is currently in two phase 2b antifungal clinical trials, was found to be a tight-binding ligand (apparent dissociation constant [K d ], 24 nM) and a potent inhibitor of cytochrome P450 sterol 14α-demethylase (CYP51) from the protozoan pathogen Trypanosoma cruzi. Moreover, VT-1161 revealed a high level of antiparasitic activity against amastigotes of the Tulahuen strain of T. cruzi in cellular experiments (50% effective concentration, 2.5 nM) and was active in vivo, causing >99.8% suppression of peak parasitemia in a mouse model of infection with the naturally drug-resistant Y strain of the parasite. The data strongly support the potential utility of VT-1161 in the treatment of Chagas disease. The structural characterization of T. cruzi CYP51 in complex with VT-1161 provides insights into the molecular basis for the compound's inhibitory potency and paves the way for the further rational development of this novel, tetrazole-based inhibitory chemotype both for antiprotozoan chemotherapy and for antifungal chemotherapy.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

New pyridine-2,3,5,6-tetracarboxylato (H₄pdtc) complexes: Synthesis, crystal structures and magnetic properties of K₂[Mn(H₂O)(pdtc)]·3H₂O 1, Na₂[M₃(H₂O)₆(pdtc)₂]·6H₂O (M=Mn 2, Co 3)

Three new pyridine-2,3,5,6-tetracarboxylato (H₄pdtc) complexes K₂[Mn(H₂O)(pdtc)]·3H₂O 1, Na₂[M₃(H₂O)₆(pdtc)₂]·6H₂O (M=Mn 2, Co 3) were obtained and characterized by single-crystal X-ray diffraction methods and magnetic measurements. The characteristic building blocks of 1–3 are the pdtc bridged stair-like chains ∞¹([M(H₂O)](pdtc){sub 3/3})²⁻, which results from the six-coordinated transition metal atoms bridged by pdtc⁴⁻ ligands. The infinite chains in 1 are assembled by hydrogen bonds into 2D supramolecular networks, which are held together by (4·8²) topological K⁺–H₂O networks to complete 3D architecture. While the stair-like chains in 2 and 3 are interconnected by trans-[M(H₂O)₄]²⁺ moieties to 2D polymeric layers, which are bridged by dimeric [Na₂(μ-H₂O)₂(H₂O)₂]²⁺ moieties to build up 3D framework. The magnetic properties of 1–3 were analyzed on the basis of (i) linear trinuclear M₃ models and (ii) the free Mn²⁺ and Co²⁺ ions with the zero-field splitting effect and spin–orbit coupling effect, respectively. - Graphic abstract: Synopsis. The characteristic building blocks and magnetic model of K₂[Mn(H₂O)(pdtc)]·3H₂O 1 and Na₂[M₃(H₂O)₆(pdtc)₂]·6H₂O (M=Mn 2, Co 3). Highlights: • The characteristic building blocks of 1–3 are the pdtc bridged stair-like chains. • The compound 2 and 3 are interlinked by trans-[M(H₂O)₄]²⁺ moieties to 2D layers. • The magnetic behavior of 1 was analyzed with zero-field splitting effects. • The magnetic behaviors were modulated with linear trinuclear model for 2 and 3.

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

Coupled structural distortions, domains, and control of phase competition in polar SmBaMn 2 O 6

Materials with coupled or competing order parameters display highly tunable ground states, where subtle perturbations reveal distinct electronic and magnetic phases. These states generally are underpinned by complex crystal structures, but the role of structural complexity in these phases often is unclear. Here we use group-theoretic methods and first-principles calculations to analyze a set of coupled structural distortions that underlie the polar charge and orbitally ordered antiferromagnetic ground state of A -site ordered SmBaMn 2 O 6 . We show that these distortions play a key role in establishing the ground state and stabilizing a network of domain wall vortices. Furthermore, we show that the crystal structure provides a knob to control competing electronic and magnetic phases at structural domain walls and in epitaxially strained thin films. These results provide new understanding of the complex physics realized across multiple length scales in SmBaMn 2 O 6 and demonstrate a framework for systematic exploration of correlated and structurally complex materials.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2021

Transforming a Simple Structure Model to Represent a Complex Dynamic System with Unknown Boundary Restraints

Imposing a boundary condition on a structure can significantly alter its dynamic properties. However, sometimes the specifics of the new boundary conditions are not known. When the effects of a boundary condition are uncertain or there is not enough information, engineers need to excite the complex structure to obtain these modified properties. In order to experimentally obtain the new properties, engineers need multiple experiments and many outputs for interpolation in order to sufficiently represent the entire structure. In this study, the researchers attached a stinger to a cantilever beam, acting as a new transverse restraint of unknown properties. This paper presents a conversion expression that predicts the dynamic behavior of any point in the system with the new boundary condition. This expression relies only on one impact hammer experiment with one output and the model of the stinger-free cantilever beam, referred to as the simple structure. Researchers estimated the Transfer Function (TRF) of the beam and compared it with an experimentally measured TRF to validate the method. The mean absolute error of the estimated TRF compared to the experimental TRF is 1.99 dB. This demonstrates the use of the proposed method for estimating unmeasured TRFs in a system with an uncertain boundary condition using a single input, single output (SISO) test and a model of the simple structure.

42 ENGINEERING↗
DOE OSTI2021

A stochastic scan strategy for grain structure control in complex geometries using electron beam powder bed fusion

Spatial control of microstructure within a three-dimensional component has been a dream of materials scientists for centuries. However, limitations in traditional manufacturing processes prevent detailed control over the distribution of microstructures in a single part. Here, we demonstrate the ability to control grain structure and crystallographic texture during metal additive manufacturing for arbitrary cross-sections of a practical size, with profound implications for the design and optimization of next-generation products. The key to this advance is a new geometry agnostic scan path algorithm that manipulates the spatial distribution of solidification conditions. Utilizing a fundamental understanding of solidification dynamics and a model of the heat transfer during processing, we have designed this algorithm to manipulate the natural competition between epitaxial dendrite growth and grain nucleation. With this algorithm, we successfully controlled the grain structure of Ni-based superalloy IN718 in the shape of the Mona Lisa.

36 MATERIALS SCIENCE↗
DOE OSTI2020

The structure of the RCAN1:CN complex explains the inhibition of and substrate recruitment by calcineurin

Regulator of calcineurin 1 (RCAN1) is an endogenous inhibitor of the Ser/Thr phosphatase calcineurin (CN). It has been shown that excessive inhibition of CN is a critical factor for Down syndrome and Alzheimer’s disease. Here, we determined RCAN1’s mode of action. Using a combination of structural, biophysical, and biochemical studies, we show that RCAN1 inhibits CN via multiple routes: first, by blocking essential substrate recruitment sites and, second, by blocking the CN active site using two distinct mechanisms. We also show that phosphorylation either inhibits RCAN1-CN assembly or converts RCAN1 into a weak inhibitor, which can be reversed by CN via dephosphorylation. This highlights the interplay between posttranslational modifications in regulating CN activity. Last, this work advances our understanding of how active site inhibition of CN can be achieved in a highly specific manner. Together, these data provide the necessary road map for targeting multiple neurological disorders.

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

Cation-Cation Interactions in [(UO2)2(OH)n](4-n) Complexes

The structures and bonding of gas-phase [(UO2)2(OH)n]4-n (n=2-6) complexes have been studied using density functional theory (DFT), MP2 and CCSD(T) methods with particular emphasis on ground state structures featuring cation-cation interactions (CCIs) between the uranyl groups. An interesting trend is observed in the stabilities of members of this series of complexes. The structures of [(UO2)2(OH)2]2+, [(UO2)2(OH)4] and [(UO2)2(OH)6]2- featuring CCIs are found at higher energies (by 3-20 kcal/mol) in comparison to their conventional μ2-dihydroxo structures. In contrast, the CCI structures of [(UO2)2(OH)3]+ and [(UO2)2(OH)5]- are respectively almost degenerate with and lower in energy than the structures with the μ2-dihydroxo format. The origin of this trend lies in the ‘symmetry’-based need to balance the coordination numbers and effective atomic charges of each uranium center. The calculated IR vibrational frequencies provide signature probes that can be used in differentiating the lowenergy structures and in experimentally confirming the existence of the structures featuring CCIs. Analysis of the bonding in the structures of [(UO2)2(OH)3]+ and [(UO2)2(OH)5]- shows that the CCIs and bridging hydroxo between the dioxo-uranium units are mainly electrostatic in nature.

Complexes↗
DOE OSTI2017

Developing Ion Mobility-Mass Spectrometry for Structural Characterization of Complex Molecular Systems, Final Report/Product Number: DOE_ER-15520-3

We have worked on developing the utility for analytical and fundamental studies in the area of ion mobility-mass spectrometry (IM-MS), including integrating enhanced molecular dynamics simulations (MDS) with IM-MS. We have continued development of cryogenic (80 K) IM-MS, which affords novel investigations of ionic water clusters and hydrated polar molecule ions. In the course ofthese studies we have provided new insights on the mechanism of electrospray ionization as well as how droplet dehydration influences the structure(s) of hydrated protons and hydronium ions, specifically how the structure(s) of the hydrated species change with the extent of hydration. We have also shown how hydration affects the structure(s) of hydrated polar molecules. A perspective on this work has just been published in Accounts of Chemical Research ; all such papers are by invitation from the Editor. We have also developed new IM-MS approaches to deconvolution of complex tandem MS spectra and we have demonstrated the utility of these approaches through several collaborations with other groups that amply illustrate the broader impact of the research. This work clearly illustrates that IM-MS is rapidly evolving as one of the most versatile and information-rich mass spectrometry-based analytical techniques. In many of the challenging areas of 21st century chemical research, the need for rapid, high-throughput, ultra-high sensitivity analytical techniques continues to grow. Tremendous gains have been made over the past two decades, much of it driven by the so-called “omics” research areas that were spawned by the human genome project. Such experimental capabilities are now spilling over into diverse areas including catalysis and nano-catalysis, polymer/materials science, petroleomics, esp. bio-mass/biofuels and renewable energy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Probing the Electronic Structure of a Thorium Nitride Complex by Solid-State 15N NMR Spectroscopy

The solid-state 15N NMR powder spectra of the thorium nitride complex, [K(18-crown-6)(THF)2][(R2N)3Th(m-15N)(Th(NR2)3] ([K][1-15N], R = SiMe3), and the thorium amide complex, [Th(NR2)3(15NH2)] (2-15N) were recorded. The spectrum for [K][1-15N] represents the first reported solid-state 15N NMR data for an actinide nitride complex. The experimentally measured tensor spans are 847 ppm for [K][1-15N] and 237 ppm for 2-15N. Both shielding tensors exhibit a near-zero asymmetry parameter, which for [K][1-15N] is consistent with a local rotational symmetry of its 15N-labelled nitride ligand. For 2-15N, the lack of asymmetry can be rationalized by a quasi-free Th-NH2 bond rotation in the solid-state. DFT calculations overestimate the tensor span somewhat for [K][1-15N], but provide isotropic shifts in good agreement with both the solid-state and solution values for both complexes. Natural localized molecular orbital (NLMO) analyses of the nuclear shielding reveal that the larger tensor span in [K][1-15N] vs. 2-15N is primarily a consequence of more pronounced covalency of the N-Th bonds, and large spin-orbit coupling due to significant Th 5f orbital contribution to those bonds, impacting the principal components of the shielding tensor perpendicular to the Th-N-Th axis. Overall, our analysis confirms the involvement of the 5f orbitals in Th-N multiple bonds, and further demonstrates the value of solid-state NMR spectroscopy for interrogating actinide-ligand bonding.

actinides, covalent bonding, Nuclear Magnetic Reso↗