Numerous promising cancer treatments currently in clinical trials rely on the production and purification of actinium-225 (225Ac), an actinide with alpha emissions that can kill cancer cells via targeted alpha therapy. To enable ongoing and future studies, and to support anticipated future demand, it is necessary to increase the supply of 225Ac. High-energy proton irradiation of thorium metal (Th0(s)) is one of the leading production methods of 225Ac. This process requires the chemical separation of microscopic amounts (μg) of 225Ac from large quantities (>10 g) of thorium. Current methods to accomplish this thorium removal step can be slow, tedious, generate large quantities of radioactive liquid waste, and require very strict control of the processing conditions. To improve this separation, we investigated the ability of four nitrate salts (NH4NO3, KNO3, RbNO3, and CsNO3) to act as selective Th4+ (aq) precipitation agents in the presence of 225Ac3+(aq) in aqueous nitric acid to allow for their separation through a simple filtration. First, we used an automated separations platform to screen the ability of these nitrate salts to precipitate Th4+. We found the Th4+ precipitation yields and amount of precipitating agent needed to maximize this yield were dependent on the identity of the precipitating agent cation. Separation studies with 225Ac3+(aq) and subsequent down-selection of the most promising Th4+ precipitating agents and conditions enabled us to develop its effective selective precipitation. We demonstrated that the separation was compatible with Th0(s) quantities that can produce medically relevant amounts of 225Ac. We observed 99.9% of Th4+(aq) could be removed via precipitation with KNO3(s) in less than two hours in the presence of co-produced isotopes. Meanwhile, other experiments demonstrated that the 225Ac3+(aq) recovery was > 97% at 1–10 g Th0(s) scale.

Atomic layer etching (ALE) is a top-down vapor-phase process that leads to self-limiting thinning of materials with an angstrom-level control. ALE has emerged as an attractive process for the wafer-scale fabrication of devices and materials with dimensional control on the nanoscale. The screening and optimization of molecular precursors for ALE processes are time- and resource-intensive. Herein, using ZnO and acetylacetone (Hacac) etching chemistry, we demonstrate a rapid thermogravimetric analysis (TGA) screening protocol with a series of β-diketones and validate its result by performing proof-of-concept ALE of ZnO with down-selected hexafluoroacetylacetone (Hhfac). The ALE process motivates the elaboration of a solvothermal and sonochemical protocol for the synthesis of Zn β-diketonate complexes under mild conditions and with excellent yields.

Various aryl and heteroaryl monomers for polysiloxane materials are finally accessible by intermolecular dehydrogenative C-H silylation between commercial (hetero)arenes and the industry-relevant triethoxysilane. The development of well-defined rhodium catalysts enables the silylation of triethoxysilane, which is known for poor reactivity in this silylation and prone to undergo the redistribution side reaction. For the silylation of electronically unactivated arenes, portionwise addition of the silane is necessary to ensure a high efficiency. Mechanistic investigation including computational study led to the isolation of two important catalytic intermediates and their dynamic interconversion, which provide mechanistic insight into the importance of portionwise addition and the intrinsic difference between arenes and heteroarenes in the silylation. In addition to their monomer roles, (hetero)aryl triethoxysilanes can be broadly utilized as versatile intermediates or coupling agents in chemical synthesis.

The bis(diethyl ether) adducts of early transition metal chlorides, MCl4(OEt2)2, serve as excellent precursors for complex inorganic and organometallic compounds due to the lability of the coordinated ethers. Previously reported MCl4(OEt2)2 (M = Zr, Nb, Ta, Mo, W) complexes have crystallized with the ethers in a trans conformation, even though computational studies have predicted that compounds of the type MX4L2 should form cis isomers. Herein, we report the crystal structure of trans-HfCl4(OEt2)2 and the synthesis and structure of cis-ReCl4(OEt2)2. The report of the crystal structure of the Hf analog completes the Groups 4-6 2nd and 3rd row series and provides structural context regarding the trans preference and observations in M-Cl and M-O bond distances that are corroborated by Shannon's ionic radii of the M(IV) cations. The isolation of the cis-Re analog provides the first structural example of a Group 7 MCl4(OEt2)2 complex, as well as the first cis complex in the presented series. Computational studies were conducted to examine the cis/trans preferences across the entire series in the context of ionic radii, ligand hardness, and steric influence.

Hexakis(neopentyl)diruthenium(III,III) [Ru2(CH2CMe3)6 or Ru2Np6], first synthesized in 1984, is a d5-d5 analogue of the classic d3-d3 M2X6 Chisholm-type, unsupported metal-metal triply-bonded Group 6 complexes. We report an alternative synthetic route to Ru2Np6 and an updated low-temperature crystal structure. The Ru-Ru bond length (2.3141(3) Å) is only 0.15 Å longer than the Mo-Mo bond in Mo2Np6, less than might be expected upon adding four electrons. The Ru-Ru bond was originally proposed to be a triple bond, which seemed inconsistent with the usual M-M bonding model. We use DFT and TD-DFT calculations on Mo2R6 and Ru2R6 (R = Me, Np) to investigate the differences in metal-metal and metal-ligand bonding between the d3-d3 and d5-d5 systems. In the Ru2R6 systems, the two RuR3 fragments adopt a pyramidalized geometry to maximize ligand-to-metal donation and to shift electron density from the strongly antibonding Ru-Ru π* orbital to the weakly bonding Ru-Ru δ orbital, thus preserving some of the Ru-Ru π bonding. In contrast, the MoR3 fragments in Mo2R6 adopt a more trigonal planar geometry to preserve the Mo-Mo π bonding. The calculated and experimental UV-vis spectra are near band-for-band matches, and the energies and orbital characters of the excitations are presented.

Hexakis(neopentyl)diruthenium(III,III) [Ru2(CH2CMe3)6 or Ru2Np6], first synthesized in 1984, is a d5-d 5 analogue of the classic d 3 -d 3 M2X6 Chisholm-type, unsupported metal-metal triply-bonded Group 6 complexes. We report an alternative synthetic route to Ru2Np6 and an updated low-temperature crystal structure. The Ru-Ru bond length (2.3141(3) & Aring;) is only 0.15 & Aring; longer than the Mo-Mo bond in Mo2Np6, less than might be expected upon adding four electrons. The Ru-Ru bond was originally proposed to be a triple bond, which seemed inconsistent with the usual M-M bonding model. We use DFT and TD-DFT calculations on Mo2R6 and Ru2R6 (R = Me, Np) to investigate the differences in metal-metal and metal-ligand bonding between the d 3-d 3 and d 5-d 5 systems. In the Ru2R6 systems, the two RuR3 fragments adopt a pyramidalized geometry to maximize ligand-to-metal donation and to shift electron density from the strongly antibonding Ru-Ru pi* orbital to the weakly bonding Ru-Ru delta orbital, thus preserving some of the Ru-Ru pi bonding. In contrast, the MoR3 fragments in Mo2R6 adopt a more trigonal planar geometry to preserve the Mo-Mo pi bonding. The calculated and experimental UV-vis spectra are near band-for-band matches, and the energies and orbital characters of the excitations are presented.

N-Heterocyclic carbenes (NHCs) have emerged as promising ligands for stabilizing metallic complexes, nanoclusters, nanoparticles (NPs) and surfaces. The carbon-metal bond between NHCs and metal atoms plays a crucial role in determining the resulting material's stability, reactivity, function, and electronic properties. Using Raman spectroscopy coupled with density functional theory calculations, we investigate the nature of carbon-metal bonding in NHC-silver and NHC-gold complexes as well as their corresponding NPs. While low wavenumbers are inaccessible to standard infrared spectroscopy, Raman detection reveals previously unreported NHC-Au/Ag bond-stretching vibrations between 154-196 cm(-1). The computationally efficient r(2)SCAN-3c method allows an excellent correlation between experimental and predicted Raman spectra which helps calibrate an accurate description of NHC-metal bonding. While pi-backbonding should stabilize the NHC-metal bond, conflicting reports for the presence and absence of pi-backbonding are seen in the literature. This debate led us to further investigate experimental and theoretical results to ultimately confirm and quantify the presence of pi-backbonding in these systems. Experimentally, an observed decrease in the NHC's CN stretching due to the population of the pi* orbital is a good indication for the presence of pi-backbonding. Using energy decomposition analysis - natural orbitals for chemical valence (EDA-NOCV), our calculations concur and quantify pi-backbonding in these NHC-bound complexes and NPs. Surprisingly, we observe that NPs are less stabilized by pi-backbonding compared to their respective complexes-a result that partially explains the weaker NHC-NP bond. The protocol described herein will help optimize metal-carbon bonding in NHC-stabilized metal complexes, nanoparticles and surfaces.

Self-sorting of two imine-based Cu(i) and Fe(ii) coordination complexes from a six-component reagent library has been achieved through solvent-free mechanochemistry.

The synthesis, characterization, and thermogravimetric analysis of tris(N,N'-di-isopropylacetamidinate)molybdenum(III), Mo(iPr-AMD)3, are reported. Mo(iPr-AMD)3 is a rare example of a homoleptic mononuclear complex of molybdenum(III) and fills a longstanding gap in the literature of transition metal(III) trisamidinate complexes. Thermogravimetric analysis (TGA) reveals excellent volatilization at elevated temperatures, pointing to potential applications as a vapor phase precursor for higher temperature atomic layer deposition (ALD), or chemical vapor deposition (CVD) growth of Mo-based materials. The measured TGA temperature window was 200-314 °C for samples in the 3-20 mg range. To validate the utility of Mo(iPr-AMD)3, we demonstrate aerosol-assisted CVD growth of MoO3 from benzonitrile solutions of Mo(iPr-AMD)3 at 500 °C using compressed air as the carrier gas. The resulting films are characterized by X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. We further demonstrate the potential for ALD growth at 200 °C with a Mo(iPr-AMD)3/Ar purge/300 W O2 plasma/Ar purge sequence, yielding ultrathin films which retain a nitride/oxynitride component. Our results highlight the broad scope utility and potential of Mo(iPr-AMD)3 as a stable, high-temperature precursor for both CVD and ALD processes.

Group 5 and 6 metal chlorides, MCl x (M = Nb, Ta, Mo, W) are easily and controllably reduced, in a stepwise fashion, by stoichiometric PhMe 2 SiH, yielding only PhMe 2 SiCl, a useful reagent, and H 2 as the byproducts.

The reaction of GaX3 with the phosphorus-centered trisphenol (2-HO-3,5-tBu2-C6H2)3P, 1, affords the cage shaped phosphonium trisphenolates XGa{(2-O-3,5-tBu2-C6H2)3PH} (X = Et, 2; Cl, 3). The new compounds are C3 symmetric and isostructural with the previously reported aluminum analogs EtAl{(2-O-3,5-tBu2-C6H2)3PH}, 5, and ClAl{(2-O-3,5-tBu2-C6H2)3PH}, 6, but display longer M-O bonds due to the lower polarity of the Ga-O bonds. Compounds 2 and 3 were characterized by IR and multinuclear NMR spectrometry and mass spectrometry, and the crystal structure of compound 2 was also determined. No single products were observed in reactions aimed at the alcoholysis of the Ga-Et group in 2 as well as in attempts to abstract the ethide group with the trityl salt [Ph3C][B(C6F5)4] or Me3SiOTf (OTf = OSO2CF3), possibly a result of the lower polarity of Ga-C bonds.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Electronic structure calculations on two dinuclear rhenium(III) carboxylate complexes, Re2(O2CH)4Cl2 and Re2(O2CCMe3)4Cl2, are presented and discussed. Allowed electronic transitions for both molecules were calculated using time-dependent density functional theory (TDDFT). The results for the pivalate dimer, Re2(O2CCMe3)4Cl2, are compared with previously reported single-crystal polarized absorption spectra obtained by Martin and co-workers (Inorg. Chem.1984, 23, 699-701). Several revisions to the previous spectral assignments are proposed.

The bis(diethyl ether) and 1,2-dimethoxyethane (dme) adducts of molybdenum(IV) chloride and tungsten(IV) chloride are valuable starting materials for a variety of synthetic inorganic and organometallic reactions. Despite the broad utility and extensive use of these 6-coordinate complexes, their syntheses remain unoptimized, and their characterization incomplete after more than three decades. While exploring the ligand exchange behaviour of trans-MoCl4(OEt2)2, we obtained single crystals of this red-orange complex and subsequently compared its structural parameters with those of the recently reported trans-WCl4(OEt2)2. Significantly improved procedures for both MoCl4(dme) and WCl4(dme) were developed, and X-ray diffraction data were obtained and analysed. The magnetic properties of the dme adducts were probed, both with Gouy and SQUID magnetometry measurements. The magnetic moment of WCl4(dme) was smaller than that of MoCl4(dme), an observation that we attribute to the greater spin-orbit coupling of tungsten. Electronic structure studies were also conducted to probe the preferential trans configuration of the diethyl ether adducts and to assign the UV-Vis spectra of the dme adducts.

The diverse structures and profound biological activities of lignan natural products have enticed significant effort in the exploration of new methodologies for their total synthesis. We have prepared γ-butyrolactone oximes from readily available δ-nitro alcohols via Boc2O mediated cyclization. The mild conditions are compatible with a wide range of functional groups, and this methodology has been applied to the total synthesis of five lignan natural products.

BACKGROUND:The heme precursors porphobilinogen (PBG) and 5-aminolevulinic acid (ALA) accumulate during overt crises of acute intermittent porphyria (AIP), and high excretion of these metabolites often continues in the asymptomatic phase.METHODS:We measured concentrations of PBG and ALA and investigated the correlation between these metabolites in plasma and urine in 10 asymptomatic AIP carriers with high excretion and in 5 healthy individuals. We quantified plasma concentrations with an HPLC-mass spectrometric method and urine concentrations with ion-exchange chromatography.RESULTS:The mean (SD) plasma concentrations of PBG and ALA in the AIP carriers were 3.1 (1.0) and 1.7 (0.7) micromol/L, respectively. The mean 8-h urinary excretion amounts of PBG and ALA in the AIP carriers were 102 (25) and 56 (18) micromol, respectively, whereas the corresponding values for healthy individuals were 2.9 (0.7) and 9.3 (1.2) micromol. The correlations between PBG and ALA values in plasma and urine of the AIP carriers were 0.678 and 0.856, respectively. The mean PBG/ALA ratio was approximately 2.0 in both plasma and urine for the AIP carriers and 0.3 in urine for the healthy individuals. The renal clearance rates for PBG and ALA were 71 (15) and 70 (13) mL/min, respectively.CONCLUSIONS:The described HPLC-mass spectrometric method enabled characterization of variations in plasma PBG and ALA in AIP carriers during an 8-h period. The renal clearances were similar for both metabolites. This method could be used to monitor AIP patients during treatment.

Pt-CeO2 catalysts have been widely studied for the vehicle emission control. Designing novel CeO2 based supports with improved physical-chemical properties has become a research hotspot to further promote the catalytic performance and stability of Pt-CeO2 catalysts. In this work, through utilizing a unique, two-step incipient wetness impregnation (T-IWI) method for ceria-zirconia-alumina (CZA-T) support preparation, a Pt single site catalyst (Pt/CZA-T) with excellent thermal stability was synthesized. Higher oxidation activity and Oxygen storage capacity (OSC) were achieved on activated Pt/CZA-T, comparing to Pt catalysts on regular CeO2/Al2O3 (Pt/CA) and one-step prepared CeZrOx/Al2O3 (Pt/CZA). Via the modification of hydrophilic/hydrophobic properties of gamma-Al2O3 by this unique T-IWI method, finer Ce0.9Zr0.1O2 particles with higher density of surface defects were formed on CZA-T, on which a higher Pt dispersion and stronger Pt-O-Ce interaction were achieved. Upon activation, smaller, well-dispersed Pt clusters on CZA-T were generated. It was concluded that the CO oxidation performance and OSC were highly related to the size of Pt clusters on different supports that we have developed. More Pt sites located at Pt cluster-CeZrOx interfaces, which were the real active sites, were responsible for the highest OSC function and CO oxidation activity of activated Pt/CZA-T catalyst.

Investigating catalytic reaction mechanisms could help guide the design of catalysts. Here, aimed at improving both the catalytic performance and SO2 resistance ability of catalysts in the selective reduction of NO by NH3 (NH3-SCR), an innovative CeO2-SiO2 mixed oxide catalyst (CeSi2) was developed based on our understanding of both the sulfur poisoning and reaction mechanisms, which exhibited excellent SO2/H2O resistance ability even in the harsh working conditions (containing 500 ppm of SO2 and 5% H2O). The strong interaction between Ce and Si (Ce-O-Si) and the abundant surface hydroxyl groups on CeSi2 not only provided fruitful surface acid sites but also significantly inhibited SO2 adsorption. The NH3-SCR performance of CeSi2 was promoted by an enhanced Eley-Rideal (E-R) mechanism in which more active acid sites were preserved under the reaction conditions and gaseous NO could directly react with adsorbed NH3. This mechanism-enhanced process was even further promoted on sulfated CeSi2. This work provides a reaction mechanism-enhanced strategy to develop an environmentally friendly NH3-SCR catalyst with superior SO2 resistance.

The true identity of the diethyl ether adduct of tungsten(IV) chloride, WCl4(Et2O)x, has been in doubt since 1985. Initially postulated as the bis-adduct, WCl4(Et2O)2, questions arose when elemental analyses were more in line with a mono-ether adduct, viz. WCl4(Et2O). It was proposed that this was due to the thermal instability of the bis-adduct. Here, we report the room-temperature X-ray crystal structure and Hirshfeld surface characteristics of trans-tetrachloridobis(diethyl ether)tungsten(IV), trans-WCl4(Et2O)2 or trans-[WCl4(C4H10O)2]. The compound crystallizes, with half of the molecule in the asymmetric unit, in the centrosymmetric space group P21/n. The W-O distance is 2.070 (2) Å, while the W-Cl distances are 2.3586 (10) and 2.3554 (10) Å.