Contracted, Not Converted: Photoluminescence Thermochromism in Ultrabright Pure Blue Emissive Hybrid Copper(I) Halide.

Thermochromic luminescent materials are promising for applications such as sensors or display technologies. Understanding the mechanism of thermochromic luminescence in these materials plays an important role for their targeted applications. Here, a 0D copper(I) halide (TMP)CuBr and 1D (TMP)AgBr (TMP = tetramethylphosphonium) are reported.

Synthesis and Characterization of Metastable Cobalt Honeycomb KCoAsO.

The Kitaev model has served as a long-sought-after target in the realization of a quantum spin liquid that could host Majorana Fermions. Such non-Abelian anyons could revolutionize quantum computing if properly implemented to overcome decoherence. A 3d electronic configuration, like Co, has been explored by theory and experimental work to design Kitaev materials.

Photoswitching dynamics of a guanidine anion receptor.

Photoswitchable molecules involving large-scale structural changes such as / photoisomerization offer remarkable opportunities for light-stimulated catch-and-release chemical separations. While the feasibility of this photochemically driven mechanism has been demonstrated in pioneering studies, the electronic excited-state relaxation processes and concomitant structural changes of such a functional photoswitcher remain largely unexplored. Here, we investigate an exceptional photoswitchable molecule, 2-pyridyl-diiminoguanidinium (2PyDIG), which exhibits strong and selective anion binding, along with an extraordinary capability for light-induced release of a guest ion.

Selective Binding and Light-Driven Release of Fluorous PF and Radioactive TcO Anions for All-to-Nothing Liquid-Liquid Extraction.

The removal of anions from aqueous media using molecular receptors in liquid-liquid extraction is a long-standing strategy to clean up contaminated water sources. Therein, high selectivity is needed to remove specific ions from mixtures of other ions, and high affinity provides extractions at low concentrations. However, the high affinity creates a conundrum by impeding the release of the ions in any stripping steps needed for further processing.

Bulk Anion Recognition Kinetically Holds Back Interfacial Adsorption.

The competition between bulk and interfacial phenomena underlies many key processes in complex chemical phenomena and transport. While competitive processes are often framed in a thermodynamic context, opportunities to leverage transient species found away from equilibrium can provide a kinetic handle to achieve unconventional reaction outcomes. In this work, we outfit an iminoguanidinium headgroup capable of selective SO complexation with alkyl tails of varying complexity to probe competitive bulk and interfacial reaction pathways and tune kinetic pathways for selective chemical separations.

Remote Sensing of Nitric Acid and Temperature via Design of Experiments, Chemometrics, and Raman Spectroscopy.

This study presents an effective method for the quantification of nitric acid (0.1-9 M) and the temperature (20-60 °C) through optimal experimental design, chemometrics, and Raman spectroscopy. Raman spectroscopy can be deployed using fiber-optic cables in hot cell environments to support processing operations in the nuclear field and industry.

A New Triketone Ligand for Extraction of Lithium from Brines.

Recovery of lithium from brines by liquid-liquid solvent extraction (LLE) with diketones and synergistic co-ligands has been investigated for decades, but industrial application has been limited. In pursuit of a ligand with improved properties, a series of ketonamides with beta-carbonyl groups were designed, synthesized, and tested in extraction of lithium from sulfate and carbonate simulants of clay mineral tailing leachates. The best performing ligand, a novel tricarbonyl amide, was characterized for lithium extraction with and without four synergistic co-ligands.

Photoisomerization mechanism of iminoguanidinium receptors from spectroscopic methods and quantum chemical calculations.

The hydrazone functional group, when coupled with a pyridyl substituent, offers a unique class of widely tunable photoswitches, whose -to- photoisomerization equilibria can be controlled through intramolecular hydrogen bonding between the N-H hydrazone donor and the pyridyl acceptor. However, little is known about the photoisomerization mechanism in this class of compounds. To address this issue, we report a pyridine-appended iminoguanidinium photoswitch that is functionally related to acylhydrazones and provides insight into the photoisomerization processes between the and configurations.

Observation of a promethium complex in solution.

Lanthanide rare-earth metals are ubiquitous in modern technologies, but we know little about chemistry of the 61st element, promethium (Pm), a lanthanide that is highly radioactive and inaccessible. Despite its importance, Pm has been conspicuously absent from the experimental studies of lanthanides, impeding our full comprehension of the so-called lanthanide contraction phenomenon: a fundamental aspect of the periodic table that is quoted in general chemistry textbooks. Here we demonstrate a stable chelation of the Pm radionuclide (half-life of 2.

Synergistic Assembly of Charged Oligomers and Amino Acids at the Air-Water Interface: An Avenue toward Surface-Directed CO Capture.

Interfaces are considered a major bottleneck in the capture of CO from air. Efforts to design surfaces to enhance CO capture probabilities are challenging due to the remarkably poor understanding of chemistry and self-assembly taking place at these interfaces. Here, we leverage surface-specific vibrational spectroscopy, Langmuir trough techniques, and simulations to mechanistically elucidate how cationic oligomers can drive surface localization of amino acids (AAs) that serve as CO capture agents speeding up the apparent rate of absorption.

Reaction Layer Formation on MgO in the Presence of Humidity.

Mineralization by MgO is an attractive potential strategy for direct air capture (DAC) of CO due to its tendency to form carbonate phases upon exposure to water and CO. Hydration of MgO during this process is typically assumed to not be rate limiting, even at ambient temperatures. However, surface passivation by hydrated phases likely reduces the CO capture capacity.

Near Quantitative Removal of Selenate and Sulfate Anions from Wastewaters by Cocrystallization with Chelating Hydrogen-Bonding Guanidinium Ligands.

Selenium (Se) has become an environmental contaminant of aquatic ecosystems as a result of human activities, particularly mining, fossil fuel combustion, and agricultural activities. By leveraging the high sulfate concentrations relative to Se oxyanions (i.e.

A Photoresponsive Receptor with a 10 Magnitude of Reversible Anion-Binding Switching.

Invited for the cover of this issue are Jeffrey Einkauf, Vyacheslav Bryantsev, Bruce Moyer, and Radu Custelcean from Oak Ridge National Laboratory. The image depicts an anion receptor functionalized with a new photoswitchable chromophore, the diiminoguanidinium group, with exceptionally strong sulfate-binding affinity that can be turned off by photoirradiation with UV light. Read the full text of the article at 10.

A Photoresponsive Receptor with a 10 Magnitude of Reversible Anion-Binding Switching.

In a leap toward anion separation that uses only energy input for binding and release cycles, we report herein a new class of photoswitchable anion receptors featuring a diiminoguanidinium functionality that displays a change of more than five orders of magnitude in switched-off binding strength towards sulfate, a representative oxyanion, upon photoirradiation with UV light. The (E,E)-2-pyridyl-diiminoguanidinium cation, synthesized as the triflate salt, binds sulfate with extraordinary strength in [D ]DMSO owing to its bidentate guanidinium hydrogen bonding, which can chelate the O-S-O edge of sulfate. Upon photoisomerization to the Z,Z isomer, the anion-binding site is essentially shut off by intramolecular hydrogen bonds to the 2-pyridyl substituents, as shown by anion-binding titrations, theoretical calculations, and X-ray structural analysis.

Spectroscopic characterization of neptunium(VI), plutonium(VI), americium(VI) and neptunium(V) encapsulated in uranyl nitrate hexahydrate.

The coordination of crystalline products resulting from the co-crystallization of Np(vi), Pu(vi), Am(vi), and Np(v) with uranyl nitrate hexahydrate (UNH) has been revealed through solid-state spectroscopic characterization via diffuse reflectance UV-Vis-NIR spectroscopy, SEM-EDS, and extended X-ray absorption fine structure (EXAFS) spectroscopy. Density functional and multireference wavefunction calculations were performed to analyze the An(vi/v)O2(NO3)2·2H2O electronic structures and to help assign the observed transitions in the absorption spectra. EXAFS show a similar coordination between the U(VI) in UNH and Np(vi) and Pu(vi); while Am resulted in a similar coordination to Am(iii), as reduction of Am(vi) occurred prior to EXAFS data being obtained.

Solid state characterization of oxidized actinides co-crystallized with uranyl nitrate hexahydrate.

Characterization of the penta- and hexavalent dioxo cations of NpO2+, NpO22+, PuO22+, and AmO22+ has been carried out by diffuse reflectance UV-Vis-NIR spectroscopy, with the first observations of NpO2+, NpO22+, and AmO22+ in the solid state. Absorbance measurements confirmed the presence of the higher actinides of Np, Pu, and Am, with shifts in their absorbance bands indicating the formation of the dinitrate species in the crystalline phase. The oxidized actinides were prepared in the solid state by co-crystallization with UO2(NO3)2·6H2O by a simple reduction in temperature.

Solubility and Complexation of the Bismuthate Ion in Nitric Acid Systems.

The dissolution rate and solubility of NaBiO have been investigated in nitric acid systems ranging from 4 to 6 M HNO and were found to be 58-76 μg/cm·d and 490-830 mM, respectively. The presence of 50 mM U(VI) drastically increased the solubility to 540-1200 mM, while rates of dissolution were relatively unchanged. The solubility of NaBiO increased with an increase in U(VI) concentrations at 4 M HNO, with log-log analysis indicating a one-to-one complex between Bi and U and infrared spectroscopic evidence monitoring uranyl stretching, suggesting complex formation.

Bismuth(iii)-thiophenedicarboxylates as host frameworks for lanthanide ions: synthesis, structural characterization, and photoluminescent behavior.

Three bismuth-2,5-thiophenedicarboxylates (Bi-TDC) and two europium-2,5-thiophenedicarboxylates (Eu-TDC) were synthesized under ambient conditions. The structures were determined through single crystal X-ray diffraction, and three of the phases were further characterized by powder X-ray diffraction, Raman spectroscopy, and thermogravimetric analysis. Reactions of bismuth nitrate, 2,5-thiophenedicarboxylate, and pyridine in an acidic solution of acetic acid and ethanol yield Hpy[Bi(TDC)2(H2O)]·1.

A General Model of Sensitized Luminescence in Lanthanide-Based Coordination Polymers and Metal-Organic Framework Materials.

Luminescent lanthanides containing coordination polymers and metal-organic frameworks hold great potential in many applications due to their distinctive spectroscopic properties. While the ability to design coordination polymers for specific functions is often mentioned as a major benefit bestowed on these compounds, the lack of a meaningful understanding of the luminescence in lanthanide coordination polymers remains a significant challenge toward functional design. Currently, the study of these compounds is based on the antenna effect as derived from molecular systems, where organic antennae are used to facilitate lanthanide-centered luminescence.

Rethinking Sensitized Luminescence in Lanthanide Coordination Polymers and MOFs: Band Sensitization and Water Enhanced Eu Luminescence in [Ln(C15H9O5)3(H2O)3]n (Ln = Eu, Tb).

A coordination polymer [Ln(C15H9O9)3(H2O)3]n (1-Ln = Eu(III), Tb(III)) assembled from benzophenonedicarboxylate was synthesized and characterized. The organic component is shown to sensitize lanthanide-based emission in both compounds, with quantum yields of 36% (Eu) and 6% (Tb). Luminescence of lanthanide coordination polymers is currently described from a molecular approach.