Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “coordination”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,603 records · Page 89
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Surprising coordination for low-valent actinides resembling uranyl( VI ) in thorium( IV ) organic hybrid layered and framework structures based on a graphene-like (6,3) sheet topology

Three thorium(IV)-based metal–organic hybrid compounds with 2D layered and 3D framework structures exhibiting graphene-like (6,3) sheet topologies were prepared with linkers with threefold symmetry. Here, these compounds contain rare and relatively anisotropic coordination environments for low-valent actinides that are similar to those often observed for high-valent actinide ions.

Li, Yuxiang↗
DOE OSTI2016

CO 2 adsorption-induced structural changes in coordination polymer ligands elucidated via molecular simulations and experiments

Aiming to elucidate guest-induced structural changes in the coordination polymer CPL-2, grand canonical Monte Carlo (GCMC) simulations were used to predict CO 2 loadings in this material, and the results were compared with experimental isotherms. Our calculations suggest that CPL-2 exhibits more pronounced CO 2 -induced structural changes than previously reported. As the initial evidence, the isotherm simulated in the previously reported CPL-2 structure (experimentally resolved from X-ray diffraction in the “as-synthesized” CPL-2) underestimated the measured CO 2 loadings at high pressure, indicating that CPL-2 might undergo structural changes that enable higher pore volumes at high pressure. GCMC simulations in CPL-2 structures considering moderate unit cell expansions reported in the literature still underestimated high-pressure experimental loadings. However, considering an incremental rotation of the CPL-2 bipyridyl pillars with increasing CO 2 pressure, we were able to trace the measured isotherm with the simulation data. Computational analysis shows that ligand rotation in CPL-2 enables higher pore volumes, which, in turn, accommodate more CO 2 as the gas pressure increases. Desorption measurements suggest that hysteresis in the CO 2 isotherm of CPL-2 may also be linked to ligand rotation, and the measured adsorption/desorption cycles show that the rotation is reversible. Based on our simulations for CPL-4 and CPL-5 and previously reported experimental data, it is likely that these materials, which differ from CPL-2 in the bipyridyl ligand, behave similarly in the presence of CO 2 . Our results help understand the behavior of these materials, which present the kind of structural changes that could be potentially exploited to enhance the CO 2 working capacity of ultra-microporous materials for carbon capture applications.

Meza-Morales, Paul J.↗
DOE OSTI2017

Capping the calix: How toluene completes cesium( i ) coordination with calix[4]pyrrole

The role of solvent in molecular recognition systems is under-researched and often ignored, especially when the solvent is considered “non-interacting”. This study concerns the role of toluene solvent in cesium(I) recognition by calix[4]pyrrole. We show that π-donor interactions bind toluene molecules onto the open face of the cation-receptor complex, thus “capping the calix.” As a result, by characterizing this unusual aromatically-saturated complex, we show how “non-interacting” aromatic solvents can directly coordinate receptor-bound cations and thus influence recognition.

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

Intermediate temperature fuel cells via an ion-pair coordinated polymer electrolyte

Fuel cells are attractive devices that convert chemical energy into electricity through the direct electrochemical reaction of hydrogen and oxygen. Intermediate temperature fuel cells operated at 200–300°C can simplify water and thermal managements, enable the use of non-precious or low-loading precious metal catalysts and provide insensitivity toward fuel and air impurities such as carbon monoxide. However, the performance of current intermediate temperature fuel cells is poor due to a lack of highly-conductive membrane electrolytes and optimal electrodes designed for these fuel cells. We demonstrate high-performing intermediate temperature fuel cells that use SnP 2 O 7 –polymer composite membranes and a quaternary ammonium-biphosphate ion-pair coordinated polymer electrolyte in the electrodes. The peak power density of the fuel cell under H 2 and O 2 reached 870 mW cm -2 at 240°C with minimal performance loss under exposure to 25% carbon monoxide.

30 DIRECT ENERGY CONVERSION↗
DOE OSTI2018

A robust two-dimensional zirconium-based luminescent coordination polymer built on a V-shaped dicarboxylate ligand for vapor phase sensing of volatile organic compounds

Here we report herein a new two-dimensional zirconium-based luminescent coordination polymer Zr 6 (sdba) 4 (μ 3 -O) 4 (μ 3 - OH) 4 (HCOO) 2 (OH) 2 (H 2 O) 2 (1) [sdba = 4,4'-sulfonyldibenzoate] exhibiting selective fluorescence responses towards a variety of volatile organic compounds upon exposure in the vapor phase. Having a unique two-dimensional signal response towards aromatic molecules, including but not limited to nitroaromatic explosives, it is capable of identification of a diverse set of analytes. In addition, compound 1 shows a remarkably high sensitivity toward acetone vapors.

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

Uranyl dication mediated photoswitching of a calix[4]pyrrole-based metal coordination cage

A set of self-assembled tri- and tetrapodal metal coordination cage structures ( cage-1 and cage-2 , respectively) constructed from the uranyl dication (UO 2 2+ ) and a dibenzoic acid functionalised cis -calix[4]pyrrole ( 1 ) are described. The inherent photochemical reactivity of the uranyl dication mediates the transformation of cage-1 to cage-2 via the activation of molecular oxygen here.

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

Novel N 6 trisbidentate ligand coordinated Ir( III ) complexes and their Ru( II ) analogs

In this work, novel N 6 -coordinated Ir( III ) complexes bearing polypyridyl ligands were synthesized and characterized. In comparison to their Ru( II ) analogs, these Ir( III ) complexes showed blue-shifted UV-vis absorption and emission spectra, but dramatically increased triplet lifetimes with much broader and stronger triplet excited-state absorption.

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

Benchtop access to anhydrous actinide N-donor coordination complexes using ionic liquids [plus supplemental information]

By dehydrating actinide salts with an ionic liquid containing a common anion and subsequent reaction with N-heterocyclic ligands, we challenge the concept that actinides prefer O- over N-donors; rather the acidic hydrogen atoms of protic solvents hinder the formation of more elusive f-element N-donor coordination complexes.

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

Interdigitated conducting tetrathiafulvalene-based coordination networks

Here, assembly of a novel ethylenedithio-tetrathiafulvalene (EDT-TTF) derivative bearing two adjacent 4-thiopyridyl groups with M(NCS)2 nodes (M = Fe, Co) leads to two isostructural 1D coordination polymers showing an enhancement of their electronic conductivity by six orders of magnitude (10 –6 vs. 10 –12 S cm –1 ), upon surface oxidation by iodine and subsequent generation of EDT-TTF-based radicals.

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

Design and synthesis of aryl-functionalized carbazole-based porous coordination cages

A subset of coordination cages have garnered considerable recent attention for their potential permanent porosity in the solid state. Herein, we report a series of functionalized carbazole-based cages of the structure type M 12 (R-cdc) 12 (M = Cr, Cu, Mo) where the functional groups include a range of aromatic substituents. Single-crystal X-ray structure determinations reveal a variety of intercage interactions in these materials, largely governed by pi–pi stacking. Density functional theory for a subset of these cages was used to confirm that the nature of the increased stability of aryl-functionalized cages is a result of inter-cage ligand interactions.

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

Ligand effects on electronic structure and bonding in U(iii) coordination complexes: a combined MCD, EPR and computational study

The trivalent oxidation state of uranium has been shown to undergo unique reactivity, from its ability to activate a variety of small molecules to its role in the catalytic reduction of ethene to ethane amongst others. Central to this unique reactivity and ability to rationally design ligands for isotope separation is the underlying uranium electronic structure. While electronic structure studies of U(IV), U(V), and U(VI) have been extensive, by comparison, analogous studies of more reduced oxidation states such as U(III) remains underdeveloped. Herein we report a combined MCD and EPR spectroscopic approach along with density functional theory and multireference wavefunction calculations to elucidate the effects of ligand perturbation in three uranium(III) Tp* complexes. Overall, the experimental and computational insight suggests that the change in ligand environment across this series of U(III) complexes resulted in only minor perturbations in the uranium electronic structure. This combined approach was also used to redefine the electronic ground state of a U(III) complex with a redox non-innocent Bipy - ligand. Overall, these studies demonstrate the efficacy of the combined experimental and theoretical approach towards evaluating electronic structure and bonding in U(III) complexes and provide important insight into the challenges in altering ligand environments to modify bonding and reactivity in uranium coordination chemistry.

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

Au 3 -to-Ag 3 coordinate-covalent bonding and other supramolecular interactions with covalent bonding strength

An efficient strategy for designing charge-transfer complexes using coinage metal cyclic trinuclear complexes (CTCs) is described herein. Due to opposite quadrupolar electrostatic contributions from metal ions and ligand substituents, [Au(m-Pz-(i-C 3 H7) 2 )] 3 ∙[Ag(m-Tz-(n-C 3 F 7 ) 2 )] 3 (Pz = pyrazolate, Tz = triazolate) has been obtained and its structure verified by single crystal X-ray diffraction – representing the 1st crystallographically-verified M 3 @M' 3 stacked adduct of monovalent coinage metal CTCs. Abundant supramolecular interactions with aggregate covalent bonding strength arise from a combination of M–M' (Au / Ag), metal–π, π–π interactions and hydrogen bonding in this charge-transfer complex, according to density functional theory analyses, yielding a computed binding energy of 66 kcal mol -1 between the two trimer moieties – a large value for intermolecular interactions between adjacent d 10 centres (nearly doubling the value for a recently claimed Au(I) / Cu(I) polar-covalent bond: Proc. Natl. Acad. Sci. U.S.A., 2017, 114, E5042) – which becomes 87 kcal mol -1 with benzene stacking. Surprisingly, DFT analysis suggests that: (a) some other literature precedents should have attained a stacked M 3 @M' 3 product akin to the one herein, with similar or even higher binding energy; and (b) a high overall intertrimer bonding energy by inferior electrostatic assistance, underscoring genuine orbital overlap between M and M' frontier molecular orbitals in such polar-covalent M–M' bonds in this family of molecules. The Au / Ag bonding is reminiscent of classical Werner-type coordinate-covalent bonds such as H 3 N: → Ag in [Ag(NH 3 ) 2 ] + , as demonstrated herein quantitatively. Solidstate and molecular modeling illustrate electron flow from the p-basic gold trimer to the p-acidic silver trimer with augmented contributions from ligand-to-ligand’ (LL'CT) and metal-to-ligand (MLCT) charge transfer.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗