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Charge and Solvent Effects on the Redox Behavior of Vanadyl Salen-Crown Complexes

The incorporation of charged groups proximal to a redox active transition metal center can impact the local electric field, altering redox behavior and enhancing catalysis. Vanadyl salen (salen = N,N'-ethylenebis(salicylideneaminato)) complexes functionalized with a crown ether containing a nonredox active metal cation (V-Na, V-K, V-Ba, V-La, V-Ce, and V-Nd) were synthesized. The electrochemical behavior of this series of complexes was investigated by cyclic voltammetry in solvents with varying polarity and dielectric constant (ε) (acetonitrile, ε = 37.5; N,N-dimethylformamide, ε = 36.7; and dichloromethane, ε = 8.93). The vanadium(V/IV) reduction potential shifted anodically with increasing cation charge compared to a complex lacking a proximal cation (ΔE_1/2 > 900 mV in acetonitrile and >700 mV in dichloromethane). In contrast, the reduction potential for all vanadyl salen-crown complexes measured in N,N-dimethylformamide was insensitive to the magnitude of the cationic charge, regardless of the electrolyte or counteranion used. Titration studies of N,N-dimethylformamide into acetonitrile resulted in cathodic shifting of the vanadium(V/IV) reduction potential with increasing concentration of N,N-dimethylformamide. Binding constants of N,N-dimethylformamide (log(K_DMF)) for the series of crown complexes show increased binding affinity in the order of V-La > V-Ba > V-K > (salen)V(O), indicating an enhancement of Lewis acid/base interaction with increasing cationic charge. The redox behavior of (salen)V(O) and (salen-OMe)V(O) (salen-OMe = N,N'-ethylenebis(3-methoxysalicylideneamine) was also investigated and compared to the crown-containing complexes. For (salen-OMe)V(O), a weak association of triflate salt at the vanadium(IV) oxidation state was observed through cyclic voltammetry titration experiments, and cation dissociation upon oxidation to vanadium(V) was identified. These studies demonstrate the noninnocent role of solvent coordination and cation/anion effects on redox behavior and, by extension, the local electric field.

A Neutral Borylene and its Conversion to a Radical by Selective Hydrogen Transfer

A successful selective reduction of X₂B-Tip (Tip = 1,3,5-ⁱPr₃-C₆H₂, X = I, Br) with KC₈ and Mg metal, respectively, in the presence of a hybrid ligand (C₆H₄(PPh₂)LSi) leads to a stable low-valent five-membered ring as a boryl radical [C₆H₄(PPh₂)LSiBTip][Br] (1) and neutral borylene [C₆H₄(PPh₂)LSiBTip] (2). Compound 2 reacts with 1,4-cyclohexadiene, resulting in hydrogen abstraction to afford the radical [C₆H₄(PPh₂)LSiB(H)Tip] (3). Quantum chemical studies reveal that compound 1 is a B-centered radical, and compound 2 is a phosphane and silylene stabilized neutral borylene in a trigonal planar environment, whereas compound 3 is an amidinate-centered radical. Although compounds 1 and 2 are stabilized by hyperconjugation and π-conjugation, they display high H-abstraction energy and basicity, respectively.

Holistic energy landscape management in 2D/3D heterojunction via molecular engineering for efficient perovskite solar cells

Constructing two-dimensional (2D) perovskite atop of 3D with energy landscape management is still a challenge in perovskite photovoltaics. Here, we report a strategy through designing a series of π-conjugated organic cations to construct stable 2D perovskites and to realize delicate energy level tunability at 2D/3D heterojunctions. As a result, the hole transfer energy barriers can be reduced both at heterojunctions and within 2D structures, and the preferable work function shift reduces charge accumulation at interface. Leveraging these insights and also benefitted from the superior interface contact between conjugated cations and poly(triarylamine) (PTAA) hole transporting layer, a solar cell with power conversion efficiency of 24.6% has been achieved, which is the highest among PTAA-based n-i-p devices to the best of our knowledge. The devices exhibit greatly enhanced stability and reproducibility. This approach is generic to several hole transporting materials, offering opportunities to realize high efficiency without using the unstable Spiro-OMeTAD.

Crystal structure and Hirshfeld surface analysis of (1H-imidazole-κN3)[N-(2-oxido-benzyl-idene)tyrosinato-κ3O,N,O']copper(II)

The title copper(II) complex, [Cu(C16H13NO4)(C3H4N2)], consists of a tridentate ligand synthesized from l-tyrosine and salicyl-aldehyde. One imidazole mol-ecule is additionally coordinating to the copper(II) ion. The crystal structure features N-H⋯O, O-H⋯O and C-H⋯O hydrogen bonds. The Hirshfeld surface analysis indicates that the most important contributions to the packing are from H⋯H (37.9%), C⋯H (28.2%) and O⋯H/H⋯O (21.2%) contacts.

Ten undescribed eremophilane and guaiane sesquiterpenes from Penicillium roqueforti

Nine undescribed eremophilane sesquiterpenes, one undescribed guaiane sesquiterpene, along with ten known analogues were isolated and identified from fungus Penicillium roqueforti, which was separated from the root soil of Hypericum beanii N. Robson collected from the Shennongjia Forestry District, Hubei Province. Their structures were elucidated on the basis of various spectroscopic analyses, mainly including NMR and HRESIMS data, ¹³C NMR calculation with DP4+ probability analyses, ECD calculations, and single-crystal X-ray diffraction experiments. Furthermore, all twenty compounds were evaluated for the in vitro cytotoxic activities against seven human tumor cell lines, and the result suggested that 14-hydroxymethylene-1(10)-ene-epi-guaidiol A exhibited considerable cytotoxic activity against the Farage (IC₅₀ < 10 μM, 48 h), SU-DHL-2, and HL-60 cells. Further mechanism study demonstrated that 14-hydroxymethylene-1(10)-ene-epi-guaidiol A could significantly promote apoptosis by inhibiting tumor cell respiration and decreasing intracellular ROS levels, thereby inducing S-phase blockade in tumor cells.

Combination of Drug Delivery Properties of PAMAM Dendrimers and Cytotoxicity of Platinum(IV) Complexes-A More Selective Anticancer Treatment?

Based on their drug delivery properties and activity against tumors, we combined PAMAM dendrimers with various platinum(IV) complexes in order to provide an improved approach of anticancer treatment. Platinum(IV) complexes were linked to terminal NH₂ moieties of PAMAM dendrimers of generation 2 (G2) and 4 (G4) via amide bonds. Conjugates were characterized by ¹H and ¹⁹⁵Pt NMR spectroscopy, ICP-MS and in representative cases by pseudo-2D diffusion-ordered NMR spectroscopy. Additionally, the reduction behavior of conjugates in comparison to corresponding platinum(IV) complexes was investigated, showing a faster reduction of conjugates. Cytotoxicity was evaluated via the MTT assay in human cell lines (A549, CH1/PA-1, SW480), revealing IC₅₀ values in the low micromolar to high picomolar range. The synergistic combination of PAMAM dendrimers and platinum(IV) complexes resulted in up to 200 times increased cytotoxic activity of conjugates in consideration of the loaded platinum(IV) units compared to their platinum(IV) counterparts. The lowest IC₅₀ value of 780 ± 260 pM in the CH1/PA-1 cancer cell line was detected for an oxaliplatin-based G4 PAMAM dendrimer conjugate. Finally, in vivo experiments of a cisplatin-based G4 PAMAM dendrimer conjugate were performed based on the best toxicological profile. A maximum tumor growth inhibition effect of 65.6% compared to 47.6% for cisplatin was observed as well as a trend of prolonged animal survival.

Novel Route to Cationic Palladium(II)-Cyclopentadienyl Complexes Containing Phosphine Ligands and Their Catalytic Activities

The Pd(II) complexes [Pd(Cp)(L)_n]_m[BF₄]_m were synthesized via the reaction of cationic acetylacetonate complexes with cyclopentadiene in the presence of BF₃∙OEt₂ (n = 2, m = 1: L = PPh₃ (1), P(p-Tol)₃, tris(ortho-methoxyphenyl)phosphine (TOMPP), tri-2-furylphosphine, tri-2-thienylphosphine; n = 1, m = 1: L = dppf, dppp (2), dppb (3), 1,5-bis(diphenylphosphino)pentane; n = 1, m = 2 or 3: 1,6-bis(diphenylphosphino)hexane). Complexes 1-3 were characterized using X-ray diffractometry. The inspection of the crystal structures of the complexes enabled the recognition of (Cp^-)⋯(Ph-group) and (Cp^-)⋯(CH₂-group) interactions, which are of C-H…π nature. The presence of these interactions was confirmed theoretically via DFT calculations using QTAIM analysis. The intermolecular interactions in the X-ray structures are non-covalent in origin with an estimated energy of 0.3-1.6 kcal/mol. The cationic palladium catalyst precursors with monophosphines were found to be active catalysts for the telomerization of 1,3-butadiene with methanol (TON up to 2.4∙10⁴ mol 1,3-butadiene per mol Pd with chemoselectivity of 82%). Complex [Pd(Cp)(TOMPP)₂]BF₄ was found to be an efficient catalyst for the polymerization of phenylacetylene (PA) (catalyst activities up to 8.9 × 10³ g_PA·(mol_Pd·h)^-1 were observed).

Molecular Design of Luminescent Complexes of Eu(III): What Can We Learn from the Ligands

The luminescent metal-organic complexes of rare earth metals are advanced materials with wide application potential in chemistry, biology, and medicine. The luminescence of these materials is due to a rare photophysical phenomenon called antenna effect, in which the excited ligand transmits its energy to the emitting levels of the metal. However, despite the attractive photophysical properties and the intriguing from a fundamental point of view antenna effect, the theoretical molecular design of new luminescent metal-organic complexes of rare earth metals is relatively limited. Our computational study aims to contribute in this direction, and we model the excited state properties of four new phenanthroline-based complexes of Eu(III) using the TD-DFT/TDA approach. The general formula of the complexes is EuL₂A₃, where L is a phenanthroline with -2-CH₃O-C₆H₄, -2-HO-C₆H₄, -C₆H₅ or -O-C₆H₅ substituent at position 2 and A is Cl^- or NO₃^-. The antenna effect in all newly proposed complexes is estimated as viable and is expected to possess luminescent properties. The relationship between the electronic properties of the isolated ligands and the luminescent properties of the complexes is explored in detail. Qualitative and quantitative models are derived to interpret the ligand-to-complex relation, and the results are benchmarked with respect to available experimental data. Based on the derived model and common molecular design criteria for efficient antenna ligands, we choose phenanthroline with -O-C₆H₅ substituent to perform complexation with Eu(III) in the presence of NO₃¯. Experimental results for the newly synthesized Eu(III) complex are reported with a luminescent quantum yield of about 24% in acetonitrile. The study demonstrates the potential of low-cost computational models for discovering metal-organic luminescent materials.

Tuning the optical and magnetic properties of lanthanide single-ion magnets using nitro-functionalized trispyrazolylborate ligands

We report the synthesis, crystal structures, photophysical and magnetic properties of 11 novel lanthanide complexes with the asymmetrically functionalized trispyrazolylborate ligand 4-nitrotrispyrazolylborate, 4-NO₂Tp^-: [Ln(4-NO₂Tp)₃] (Ln = La-Dy, except Pm). In-depth photophysical characterization of the ligands via luminescence, reflectance and absorption spectroscopic techniques, decay lifetimes, quantum yields supported by time-dependent density functional theory (TD-DFT) and natural bond order (NBO) analysis reveal that n-NO₂Tp^- ligands are dominated by intra-ligand charge transfer (ILCT) transitions and that second-sphere interactions are critical to the stabilization of the T₁ state of n-NO₂Tp^- ligands and hence their ability to sensitize Ln³⁺ emission. The luminescence properties of the complexes indicate that 4-NO₂Tp^- is a poor sensitizer of Ln³⁺ emission, unlike 3-NO₂Tp^-. Moreover, [Nd(4-NO₂Tp)₃] (crystallized as a hexane solvate) displays single-molecule magnet (SMM) properties, with longer relaxation times and larger barrier than the non-functionalized [NdTp₃], attributed to the addition of the NO₂-group and subsequent rigidification of the molecular structure.

Woven, Polycatenated, or Cage Structures: Effect of Modulation of Ligand Curvature in Heteroleptic Uranyl Ion Complexes

Combining the flexible zwitterionic dicarboxylate 4,4'-bis(2-carboxylatoethyl)-4,4'-bipyridinium (L) and the anionic dicarboxylate ligands isophthalate (ipht^2-) and 1,2-, 1,3-, or 1,4-phenylenediacetate (1,2-, 1,3-, and 1,4-pda^2-), of varying shape and curvature, has allowed isolation of five uranyl ion complexes by synthesis under solvo-hydrothermal conditions. [(UO₂)₂(L)(ipht)₂] (1) and [(UO₂)₂(L)(1,2-pda)₂]·2H₂O (2) have the same stoichiometry, and both crystallize as monoperiodic coordination polymers containing two uranyl-(anionic carboxylate) strands united by L linkers into a wide ribbon, all ligands being in the divergent conformation. Complex 3, [(UO₂)₂(L)(1,3-pda)₂]·0.5CH₃CN, with the same stoichiometry but ligands in a convergent conformation, is a discrete, binuclear species which is the first example of a heteroleptic uranyl carboxylate coordination cage. With all ligands in a divergent conformation, [(UO₂)₂(L)(1,4-pda)(1,4-pdaH)₂] (4) crystallizes as a sinuous and thread-like monoperiodic polymer; two families of chains run along different directions and are woven into diperiodic layers. Modification of the synthetic conditions leads to [(UO₂)₄(LH)₂(1,4-pda)₅]·H₂O·2CH₃CN (5), a monoperiodic polymer based on tetranuclear (UO₂)₄(1,4-pda)₄ rings; intrachain hydrogen bonding of the terminal LH⁺ ligands results in diperiodic network formation through parallel polycatenation involving the tetranuclear rings and the LH⁺ rods. Complexes 1-3 and 5 are emissive, with complex 2 having the highest photoluminescence quantum yield (19%), and their spectra show the maxima positions usual for tris-κ²O,O'-chelated uranyl cations.

Multifunctional Zn(II) Coordination Polymer as Highly Selective Fluorescent Sensor and Adsorbent for Dyes

A new Zn(II)-based coordination polymer (1) comprising the Schiff base ligand obtained by the condensation of 5-aminosalicylic acid and salicylaldehyde has been synthesized. This newly synthesized compound has been characterized by analytical and spectroscopic methods, and finally, by single-crystal X-ray diffraction technique in this study. The X-ray analysis reveals a distorted tetrahedral environment around the central Zn(II) center. This compound has been used as a sensitive and selective fluorescent sensor for acetone and Ag⁺ cations. The photoluminescence measurements indicate that in the presence of acetone, the emission intensity of 1 displays quenching at room temperature. However, other organic solvents caused meagre changes in the emission intensity of 1. Additionally, the fluorescence intensity of 1 has been examined in the presence of different ketones viz. cyclohexanone, 4-heptanone, and 5-nonanone, to assess the interaction between the C=O group of the ketones and the molecular framework of 1. Moreover, 1 displays a selective recognition of Ag⁺ in the aqueous medium by an enhancement in its fluorescence intensity, representing its high sensitivity for the detection of Ag⁺ ions in a water sample. Additionally, 1 displays the selective adsorption of cationic dyes (methylene blue and rhodamine B). Hence, 1 showcases its potential as an excellent luminescent probe to detect acetone, other ketones, and Ag⁺ with an exceptional selectivity, and displaying a selective adsorption of cationic dye molecules.

Structural and Functional Diversity in Rigid Thiosemicarbazones with Extended Aromatic Frameworks: Microwave-Assisted Synthesis and Structural Investigations

The long-standing interest in thiosemicarbazones (TSCs) has been largely driven by their potential toward theranostic applications including cellular imaging assays and multimodality imaging. We focus herein on the results of our new investigations into: (a) the structural chemistry of a family of rigid mono(thiosemicarbazone) ligands characterized by extended and aromatic backbones and (b) the formation of their corresponding thiosemicarbazonato Zn(II) and Cu(II) metal complexes. The synthesis of new ligands and their Zn(II) complexes was performed using a rapid, efficient and straightforward microwave-assisted method which superseded their preparation by conventional heating. We describe hereby new microwave irradiation protocols that are suitable for both imine bond formation reactions in the thiosemicabazone ligand synthesis and for Zn(II) metalation reactions. The new thiosemicarbazone ligands, denoted HL, mono(4-R-3-thiosemicarbazone)quinone, and their corresponding Zn(II) complexes, denoted ZnL₂, mono(4-R-3-thiosemicarbazone)quinone, where R = H, Me, Ethyl, Allyl, and Phenyl, quinone = acenapthnenequinone (AN), aceanthrenequinone (AA), phenanthrenequinone (PH), and pyrene-4,5-dione (PY) were isolated and fully characterized spectroscopically and by mass spectrometry. A plethora of single crystal X-ray diffraction structures were obtained and analyzed and the geometries were also validated by DFT calculations. The Zn(II) complexes presented either distorted octahedral geometry or tetrahedral arrangements of the O/N/S donors around the metal center. The modification of the thiosemicarbazide moiety at the exocyclic N atoms with a range of organic linkers was also explored, opening the way to bioconjugation protocols for these compounds. The radiolabeling of these thiosemicarbazones with ⁶⁴Cu was achieved under mild conditions for the first time: this cyclotron-available radioisotope of copper (t_1/2 = 12.7 h; β+ 17.8%; β- 38.4%) is well-known for its proficiency in positron emission tomography (PET) imaging and for its theranostic potential, on the basis of the preclinical and clinical cancer research of established bis(thiosemicarbazones), such as the hypoxia tracer ⁶⁴Cu-labeled copper(diacetyl-bis(N4-methylthiosemicarbazone)], [⁶⁴Cu]Cu(ATSM). Our labeling reactions proceeded in high radiochemical incorporation (>80% for the most sterically unencumbered ligands) showing promise of these species as building blocks for theranostics and synthetic scaffolds for multimodality imaging probes. The corresponding "cold" Cu(II) metalations were also performed under the mild conditions mimicking the radiolabeling protocols. Interestingly, room temperature or mild heating led to Cu(II) incorporation in the 1:1, as well as 1:2 metal: ligand ratios in the new complexes, as evident from extensive mass spectrometry investigations backed by EPR measurements, and the formation of Cu(L)₂-type species prevails, especially for the AN-Ph thiosemicarbazone ligand (L^-). The cytotoxicity levels of a selection of ligands and Zn(II) complexes in this class were further tested in commonly used human cancer cell lines (HeLa, human cervical cancer cells, and PC-3, human prostate cancer cells). Tests showed that their IC₅₀ levels are comparable to that of the clinical drug cis-platin, evaluated under similar conditions. The cellular internalizations of the selected ZnL₂-type compounds Zn(AN-Allyl)₂, Zn(AA-Allyl)₂, Zn(PH-Allyl)₂, and Zn(PY-Allyl)₂ were evaluated in living PC-3 cells using laser confocal fluorescent spectroscopy and these experiments showed exclusively cytoplasmic distributions.

From the Spectroscopic Reassessment of Authentic Alkaloid Samples to the Molecular Networking-Guided Discovery of Criophylline-Related Analogues from Callichilia inaequalis

The molecular network-guided exploration of the alkaloid extract of Callichilia inaequalis stems revealed a cluster attributed tentatively to dimeric monoterpene indole alkaloids of the rare criophylline subtype, initiating the dual study reported herein. A patrimonial-themed portion of this work was aimed at performing a spectroscopic reassessment of criophylline (1), a monoterpene bisindole alkaloid for which the nature of the inter-monomeric connectivity and configurational assignments have remained dubious. A targeted isolation of the entity annotated as criophylline (1) was undertaken to strengthen the available analytical evidence. An extensive set of spectroscopic data was acquired from the authentic sample of criophylline (1a) isolated earlier by Cavé and Bruneton. These spectroscopic studies proved the samples to be identical, and the complete structure of criophylline could be assigned, half a century after it was first isolated. The absolute configuration of andrangine (2) was also ascertained based on a TDDFT-ECD approach from the authentic sample. The forward-looking aspect of this investigation resulted in the characterization of two new criophylline derivatives from C. inaequalis stems, namely, 14'-hydroxycriophylline (3) and 14'-O-sulfocriophylline (4). Their structures, including absolute configurations, were elucidated by analysis of NMR and MS spectroscopic data and by ECD analysis. Notably, 14'-O-sulfocriophylline (4) is the first sulfated monoterpene indole alkaloid to have been reported. The antiplasmodial activity against the chloroquine-resistant strain of Plasmodium falciparum FcB1 was determined for criophylline and its two new analogues.

Crystal Structures and Property Measurements of Rare Earth Magnesium Thiosilicates Synthesized via Flux Crystal Growth Utilizing the Boron Chalcogen Mixture (BCM) Method

Nine new rare earth magnesium-containing thiosilicates of the formula RE₃Mg_0.5SiS₇ (Ln = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er) were synthesized in an alkali halide flux using the boron chalcogen mixture (BCM) method. Crystals of high quality were produced, and their structures were determined by single-crystal X-ray diffraction. The compounds crystallize in the hexagonal crystal system in the P6₃ space group. Phase pure powders of the compounds were used for magnetic susceptibility measurements and for second-harmonic generation (SHG) measurements. Magnetic measurements indicate that Ce₃Mg_0.5SiS₇, Sm₃Mg_0.5SiS₇, and Dy₃Mg_0.5SiS₇ exhibit paramagnetic behavior with a negative Weiss temperature over the 2-300 K temperature range. SHG measurements of La₃Mg_0.5SiS₇ demonstrated SHG activity with an efficiency of 0.16 times the standard potassium dihydrogen phosphate (KDP).

Bandgap modification in 0D tellurium iodide perovskite derivatives via incorporation of polyiodide species

Halide perovskites provide a versatile platform for exploring the effect of non-covalent interactions, including halogen bonding, on material properties such as band gap, luminescence, and frontier orbital landscape. Herein we report six new zero-dimensional tellurium iodide perovskite derivatives, consisting of [TeI₆]^2- octahedra charge balanced by one of several X-Py cations (X = H, Cl, Br, I, and Py = pyridinium). These compounds also feature robust halogen bonding between [TeI₆]^2- octahedra and polyiodides in the form of I₂ (1-4), I₃ ^- (5), or adjacent octahedra (4 and 6). These relatively strong non-covalent interactions (NCIs) are modeled by natural bond order (NBO) and second order perturbation theory (SOPT) calculations. NCIs are responsible for reducing the bandgap of these materials (measured via diffuse reflectance spectroscopy) relative to those without polyiodide species. They also affect inner sphere bonding in the metal halide, exacerbating [TeI₆]^2- octahedron asymmetry as compared to previously published compounds, with greater asymmetry correlating with higher van der Waals overlap of halogen-halogen contacts. We also demonstrate the ability of hydrogen and carbon bonding (which dominates in the absence of polyiodides) to affect inner sphere tellurium iodide bonding and octahedral symmetry.

Structure Elucidation and Biosynthesis of Nannosterols A and B, Myxobacterial Sterols from Nannocystis sp. MNa10993

Myxobacteria represent an underinvestigated source of chemically diverse and biologically active secondary metabolites. Here, we report the discovery, isolation, structure elucidation, and biological evaluation of two new bacterial sterols, termed nannosterols A and B (1, 2), from the terrestrial myxobacterium Nannocystis sp. (MNa10993). Nannosterols feature a cholestanol core with numerous modifications including a secondary alcohol at position C-15, a terminal vicinal diol side chain at C-24-C-25 (1, 2), and a hydroxy group at the angular methyl group at C-18 (2), which is unprecedented for bacterial sterols. Another rare chemical feature of bacterial triterpenoids is a ketone group at position C-7, which is also displayed by 1 and 2. The combined exploration based on myxobacterial high-resolution secondary metabolome data and genomic in silico investigations exposed the nannosterols as frequently produced sterols within the myxobacterial suborder of Nannocystineae. The discovery of the nannosterols provides insights into the biosynthesis of these new myxobacterial sterols, with implications in understanding the evolution of sterol production by prokaryotes.

17-β-Estradiol-β-Cyclodextrin Complex as Solid: Synthesis, Structural and Physicochemical Characterization

17-β-estradiol (EST) is the most potent form of naturally occurring estrogens; therefore, it has found a wide pharmaceutical application. The major problem associated with the use of EST is its very low water solubility, resulting in poor oral bioavailability. To overcome this drawback, a complexation with cyclodextrins (CD) has been suggested as a solution. In this work, the host-guest inclusion complex between the ß-CD and EST has been prepared using four different methods. The obtained samples have been deeply characterized using ¹³C CP MAS solid state NMR, PXRD, FT-IR, TGA, DSC, and SEM. Using SCXRD, the crystal structure of the complex has been determined, being to the best of our knowledge the first solved crystal structure of an estrogen/CD complex. The periodic DFT calculations of NMR properties using GIPAW were found to be particularly helpful in the analysis of disorder in the solid state and interpretation of experimental NMR results. This work highlights the importance of a combined ssNMR/SCXRD approach to studying the structure of the inclusion complexes formed by cyclodextrins.

Angular Regioselective Synthesis of Varied Functionalized Hexahydro-1,2,4-triazolo[4,3-a]quinazolin-9-ones and Their Antiproliferative Action

New 2-thioxopyrimidin-4-ones capable of participating in regioselective reactions with functionally diverse hydrazonoyl chlorides towards angular regioisomers, rather than linear ones, were designed and synthesized to form stereoisomeric cis- and trans-hexahydro [1,2,4]triazolo[4,3-a]quinazolin-9-ones to be tested as antitumor candidates. The angular regiochemistry of the products was verified through crystallographic experiments and NMR studies. In addition, the regioselectivity of the reaction was found to be independent of the stereochemistry of the used 2-thioxopyrimidin-4-one. Only compound 4c demonstrated satisfactory growth inhibition against all the cancer cells used among all the produced drugs.

Flux Crystal Growth of the Extended Structure Pu(V) Borate Na2(PuO2)(BO3)

As part of our exploration of plutonium-containing materials as potential nuclear waste forms, we report the first extended structure Pu(V) material and the first Pu(V) borate. Crystals of Na₂(PuO₂)(BO₃) were grown out of mixed hydroxide/boric acid flux and found to crystallize in the orthorhombic space group Cmcm with lattice parameters of a = 9.9067(4) Å, b = 6.5909(2) Å, and c = 6.9724(2) Å. Na₂(PuO₂)(BO₃) adopts a layered structure in which layers of PuO₂(BO₃)^2- are separated by sodium cations. Plutonium is found in a pentagonal bipyramidal coordination environment, with axial Pu(V)-O plutonyl bond lengths of 1.876(3) Å and equatorial Pu-O bond lengths ranging from 2.325(5) to 2.467(3) Å. We find that the Pu(V)-O plutonyl bond lengths are approximately 0.1 Å longer than the reported Pu(VI)-O plutonyl bond lengths and shorter by approximately 0.033 Å than the corresponding U(V) uranyl bond lengths. Raman spectroscopy on single crystals was used to determine the PuO₂⁺ plutonyl stretching and the equatorial breathing mode frequencies of the pentagonal bipyramidal coordination environment around plutonium. Density functional theory calculations were used to calculate the Raman spectrum to help identify the Raman bands at 690 and 630 cm^-1 as corresponding to the plutonyl(V) ν1 stretch and the equatorial PuO₅ breathing mode, respectively. UV-vis measurements on single crystals indicate semiconducting behavior with a band gap of ∼2.60 eV.

Molar-Ratio-Dependent Coordination Assembly of Organoiridium(III)-Octatungstate Complexes in Aqueous Solution

We scrutinized the speciation of Cp*Ir-containing tungsten oxide clusters (Cp* is pentamethylcyclopentadienyl anion) in aqueous mixtures of [(Cp*IrCl)₂(μ-Cl)₂] and Na₂WO₄ in varying molar ratios. ¹H nuclear magnetic resonance (NMR) spectroscopy revealed the formation of three distinct Cp*Ir-polyoxotungstate species in the reaction solution, and they were isolated as Na₄[(Cp*Ir)₂(μ-OH)₃]₂[(Cp*Ir)₂H₂W₈O₃₀] (1), [(Cp*Ir)₂(μ-OH)₃]₂[(Cp*Ir)₂{Cp*Ir(OH₂)}₂H₂W₈O₃₀] (2), and [(Cp*Ir)₂{Cp*Ir(OH₂)}₂{Cp*Ir(OH₂)₂}₂H₂W₈O₃₀](NO₃)₂ (3) from the mixtures in which iridium concentration is less than, equal to, and more than the tungsten concentration, respectively. These results show the octatungstate [H₂W₈O₃₀]^10- anion is the major polyoxotungstate species in the presence of {Cp*Ir}²⁺ cations, and it has high nucleophilicity enough to bind up to six {Cp*Ir}²⁺ cations on its surfaces producing a cationic Cp*Ir-octatungstate complex. The octatungstate anion was also generated from the reaction of [(Cp*IrCl)₂(μ-Cl)₂] and methylammonium paratungstate-B, (CH₃NH₃)₁₀[H₂W₁₂O₄₂], and was isolated as a methylamine-coordinated complex (CH₃NH₃)₂[(Cp*Ir)₂{Cp*Ir(NH₂CH₃)}₂H₂W₈O₃₀] (4), indicating {Cp*Ir}²⁺ cations function as a structure-directing agent that converts tungsten species into octatungstate anions in aqueous solution. In addition, the coordination environment of {Cp*Ir}²⁺ can be further modified by coordination with pyridine forming [{Cp*Ir(NC₅H₅)}₂(μ-OH)₂][(Cp*Ir)₂{Cp*Ir(NC₅H₅)}₂H₂W₈O₃₀] (5).

NMR-Relaxometric Investigation of Mn(II)-Doped Polyoxometalates in Aqueous Solutions

Solution behavior of K;₅[(Mn(H₂O))PW₁₁O₃₉]·7H₂O (1), Na_3.66(NH₄)_4.74H_3.1[(Mn^II(H₂O))_2.75(WO(H₂O))_0.25(α-B-SbW₉O₃₃)₂]·27H₂O (2), and Na_4.6H_3.4[(Mn^II(H₂O)₃)₂(WO₂)₂(β-B-TeW₉O₃₃)₂]·19H₂O (3) was studied with NMR-relaxometry and HPLC-ICP-AES (High Performance Liquid Chromatography coupled with Inductively Coupled Plasma Atomic Emission Spectroscopy). According to the data, the [(Mn(H₂O))PW₁₁O₃₉]^5- Keggin-type anion is the most stable in water among the tested complexes, even in the presence of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA). Aqueous solutions of 2 and 3 anions are less stable and contain other species resulting from dissociation of Mn²⁺. Quantum chemical calculations show the change in Mn²⁺ electronic state between [Mn(H₂O)₆]²⁺ and [(Mn(H₂O))PW₁₁O₃₉]^5-.

The polymorph landscape of Dabigatran etexilate mesylate: Taking the challenge to bring a metastable polymorph to market

Dabigatran etexilate mesylate is polymorphic and can exist in different crystalline forms. Two polymorphs have been encountered during the development of this drug substance, namely anhydrous form I and anhydrous form II. Additionally, a hemihydrate was observed, if larger amounts of water were present during crystallization in the salt formation step. Finally, a high temperature form III can be obtained by heating anhydrous form I above 150°C. All three at room-temperature accessible forms were characterized by means of microscopy, X-ray powder diffraction, thermal analysis, IR- and Raman spectroscopy. In addition, solubility parameters (equilibrium solubility and intrinsic dissolution rate, heat of solution) were collected on all three forms. The crystal structure of all three at room-temperature accessible forms could be obtained using electron diffraction. Anhydrous form I has a monoclinic crystal lattice (C2/c), anhydrous form II a triclinic one (P1¯), and the hemihydrate crystallizes also in a monoclinic space group (P2/c). From the obtained data there is clear evidence that anhydrous form II is thermodynamically more stable than anhydrous form I. Form I and form II are monotropically related to each other indicating that they may coexist over a wide temperature range. The hemihydrate is a completely independent crystalline modification of dabigatran etexilate mesylate. It is another thermodynamically stable form and structurally not related to the two anhydrous forms. The hemihydrate melts at ca. 125°C, there is no conversion to either anhydrous form I or form II upon dehydration. The high temperature form III is enantiotropically related to form I and only stable above the phase transition temperature at ca. 150°C and its melting point at ca. 183°C. The energy difference between anhydrous form I and form II was found to be only 2.5 - 3.0 J/g. Both forms have very similar aqueous solubility characteristics. Although anhydrous form II is the thermodynamically more stable form, anhydrous form I was chosen for development. The selection of form I for development was mainly based on the superior bulk processing properties of anhydrous form I in drug substance synthesis and further drug product processing as well as its slightly better chemically stability in pivotal long term stability studies. Anhydrous form I, although meta stable, is still stable enough that conversion to the more stable form II can occur only to a limited extent during drug substance synthesis and drug product manufacturing. From long term stability data on both bulk drug substance as well as drug product, there is no indication that form I transforms to form II during storage. Even under stress conditions where form I was stored up to 4 weeks at 70°C, no conversion to form II was observed.

Self-Activation of Inorganic-Organic Hybrids Derived through Continuous Synthesis of Polyoxomolybdate and para-Phenylenediamine Enables Very High Lithium-Ion Storage Capacity

Inorganic-organic hybrid materials with redox-active components were prepared by an aqueous precipitation reaction of ammonium heptamolybdate (AHM) with para-phenylenediamine (PPD). A scalable and low-energy continuous wet chemical synthesis process, known as the microjet process, was used to prepare particles with large surface area in the submicrometer range with high purity and reproducibility on a large scale. Two different crystalline hybrid products were formed depending on the ratio of molybdate to organic ligand and pH. A ratio of para-phenylenediamine to ammonium heptamolybdate from 1 : 1 to 5 : 1 resulted in the compound [C₆ H₁₀ N₂ ]₂ [Mo₈ O₂₆ ] ⋅ 6 H₂ O, while higher PPD ratios from 9 : 1 to 30 : 1 yielded a composition of [C₆ H₉ N₂ ]₄ [NH₄ ]₂ [Mo₇ O₂₄ ] ⋅ 3 H₂ O. The electrochemical behavior of the two products was tested in a battery cell environment. Only the second of the two hybrid materials showed an exceptionally high capacity of 1084 mAh g^-1 at 100 mA g^-1 after 150 cycles. The maximum capacity was reached after an induction phase, which can be explained by a combination of a conversion reaction with lithium to Li₂ MoO₄ and an additional in situ polymerization of PPD. The final hybrid material is a promising material for lithium-ion battery (LIB) applications.

Scissor-like Au4Cu2 Cluster with Phosphorescent Mechanochromism and Thermochromism

Reaction of [Au(tht)2](ClO4) (tht = tetrahydrothiophene), [Cu(CH3CN)4](ClO4), 3,6-di-tert-butyl-1,8-diethynyl-9H-carbazole (H3decz), and bis(2-diphenylphosphinophenyl)ether (POP) in the presence of triethylamine (NEt3) gave the cluster complex Au4Cu2(decz)2(POP)2 as yellow crystals. As revealed by X-ray crystallography, the Au4Cu2 cluster exhibits scissor-like structure sustained by two decz and two POP ligands and stabilized by Au-Cu and Au-Au interactions. The Au4Cu2 cluster shows bright yellow to orange photoluminescence upon irradiation at >300 nm, arising from 3[π (decz)→5d (Au)] 3LMCT (ligand-to-metal charge transfer) and 3[π→π* (decz)] 3IL (intraligand) triplet states as revealed by theoretical and computational studies. When it is mechanically ground, reversible phosphorescence conversion from yellow to red is observed owing to more compact molecular packing and thus stronger intermetallic interaction. Variable-temperature luminescence studies reveal that it displays distinct red-shifts of the emission whether the temperature is elevated or lowered from ambient temperature, suggestive of exceptional thermochromic phosphorescence characteristics.

Antitumor copper(II) complexes with hydroxyanthraquinones and N,N-heterocyclic ligands

Five ternary copper(II) complexes, [Cu₂(phen)₂(L1)(ClO₄)₂] (1), [Cu₂(phen)₂(L1)(DMSO)₂](PF6)₂ (2), [Cu₂(bpy)₂(L1)(ClO₄)₂(H₂O)₂] (3), [Cu₂(dmp)₂(L1)(ClO₄)₂(H₂O)₂] (4), and [Cu(phen)(L2)]₂(ClO₄)₂ (5), in which phen = 1,10-phenanthroline, bpy = 2,2'-bipyridine, dmp = 2,9-dimethyl-1,10-phenanthroline, H₂L1 = 1,4-dihydroxyanthracene-9,10-dione and HL2 = 1-hydroxyanthracene-9,10-dione, DMSO = dimethylsulfoxide, were synthesized and fully characterized. Complex 2 was obtained through the substitution of perchlorate for DMSO. When two hydroxyquinone groups are present, L1 makes a bridge between two Cu(II) ions, which also bind two nitrogens of the respective diimine ligand. The compounds bind to calf thymus DNA and oxidatively cleave pUC19 DNA according to the following order of activity 1 > 4-5 > 3. Furthermore, complexes 1, 3, 4 and 5 inhibit topoisomerase-I activity and the growth of myelogenous leukemia cells with the IC₅₀ values of 1.13, 10.60, 0.078, and 1.84 μmol L^-1, respectively. Complexes 1 and 4 are the most active in cancer cells and in DNA cleavage.

Electron crystallography and dedicated electron-diffraction instrumentation

Electron diffraction (known also as ED, 3D ED or microED) is gaining momentum in science and industry. The application of electron diffraction in performing nano-crystallography on crystals smaller than 1 µm is a disruptive technology that is opening up fascinating new perspectives for a wide variety of compounds required in the fields of chemical, pharmaceutical and advanced materials research. Electron diffraction enables the characterization of solid compounds complementary to neutron, powder X-ray and single-crystal X-ray diffraction, as it has the unique capability to measure nanometre-sized crystals. The recent introduction of dedicated instrumentation to perform ED experiments is a key aspect of the continued growth and success of this technology. In addition to the ultra-high-speed hybrid-pixel detectors enabling ED data collection in continuous rotation mode, a high-precision goniometer and horizontal layout have been determined as essential features of an electron diffractometer, both of which are embodied in the Eldico ED-1. Four examples of data collected on an Eldico ED-1 are showcased to demonstrate the potential and advantages of a dedicated electron diffractometer, covering selected applications and challenges of electron diffraction: (i) multiple reciprocal lattices, (ii) absolute structure of a chiral compound, and (iii) R-values achieved by kinematic refinement comparable to X-ray data.

High-throughput phase elucidation of polycrystalline materials using serial rotation electron diffraction

Rapid phase elucidation of polycrystalline materials is essential for developing new materials of chemical, pharmaceutical and industrial interest. Yet, the size and quantity of many crystalline phases are too small for routine X-ray diffraction analysis. This has become a workflow bottleneck in materials development, especially in high-throughput synthesis screening. Here we demonstrate the application of serial rotation electron diffraction (SerialRED) for high-throughput phase identification of complex polycrystalline zeolite products. The products were prepared from a combination of multiple framework T atoms ([Si,Ge,Al] or [Si,Ge,B]) and a simple organic structure-directing agent. We show that using SerialRED, five zeolite phases can be identified from a highly complex mixture. This includes phases with ultra-low contents undetectable using X-ray diffraction and phases with identical crystal morphology and similar unit cell parameters. By automatically and rapidly examining hundreds of crystals, SerialRED enables high-throughput phase analysis and allows the exploration of complex synthesis systems. It provides new opportunities for rapid development of polycrystalline materials.

Crystal and mol-ecular structure of 4-fluoro-1H-pyrazole at 150 K

Only two 4-halo-1H-pyrazole crystal structures are known to date (chloro and bromo, the structure of 4-iodo-1H-pyrazole has not been reported yet). The triclinic structure of 4-fluoro-1H-pyrazole, C₃H₃FN₂ (P ), reported here is not isomorphous with those of the chloro and bromo analogues (which are isomorphous, ortho-rhom-bic Pnma). To avoid sublimation during the measurement, diffraction data were collected at 150 K. Two crystallographically unique 4-fluoro-1H-pyrazole moieties linked by an N-H⋯N hydrogen bond are found in the asymmetric unit. Unlike the trimeric supra-molecular motifs found in the structures of the chloro and bromo analogues, 4-fluoro-1H-pyrazole forms one-dimensional chains by inter-molecular hydrogen bonding in the crystal.

Synthesis and Structure of COE-11, a New Borosilicate Zeolite with a Two-Dimensional Pore System of 12-Ring Channels

The new zeolite, COE-11, was synthesized at 155 °C to 168 °C by hydrothermal synthesis from a reaction mixture of SiO2/tetraethylammonium hydroxide/H3BO3/NaOH/H2O. Because tetraethylammonium is an unspecific structure directing agent, COE-11 crystallizes in all cases together with at least one impurity phase from a selection of phases: zeolite types *BEA, CHA, FER, MFI, MOR, MTW; the layered silicates magadiite and kenyaite; and searlsite and silica polymorph quartz. The crystal structure was solved from 3D electron diffraction (3D ED) data. Subsequent structure refinements of X-ray powder diffraction (PXRD) data and single crystal electron diffraction data converged to residual values of RF = 0.039, chi2 = 3.6 (PXRD) and RF = 21.81% (3D ED) confirming the structure model. COE-11 crystallizes in space group C2 with unit cell dimensions of a0 = 17.3494(11) Å, b0 = 17.3409(11) Å, c0 = 14.2789(4) Å and β = 113.762(2) °. The structure of COE-11 is characterized by a microporous borosilicate framework with intersecting, highly elliptical 12-ring channels running parallel (110) and (1–10) and forming a two-dimensional pore system. The Rietveld refinement provided a hint that boron partly substitutes silicon on three specific T sites of the framework. The idealized chemical composition of as-made COE-11 is [(CH3CH2)4N]4[B4Si62O132] per unit cell. Physico-chemical characterization using solid-state NMR spectroscopy, SEM, TG-DTA, and ATR-FTIR spectroscopy confirmed that COE-11 is a microporous borosilicate zeolite. COE-11 is structurally closely related to zeolite beta polymorph B but differs concerning the dimensionality of the pore system, which is 2D instead of 3D.

Bis(2-phenylpyridinato,-C2′,N)[4,4′-bis(4-Fluorophenyl)-6,6′-dimethyl-2,2′-bipyridine] Iridium(III) Hexafluorophosphate

A new bis cyclometallated Ir(III) phosphor, [Ir(ppy)2L]PF6 (ppy = 2-phenylpyridine, L = 4,4′-bis(4-fluorophenyl)-6,6′-dimethyl-2,2′-bipyridine was prepared and structurally characterized in the solid state (X-ray diffraction) and solution (1 and 2D NMR spectroscopy). The compound exhibited yellow photoluminescence (λem = 562 nm). The quantum yield Φ was solvent-dependent (5% in acetonitrile and 19% in dichloromethane solutions, respectively).

Comparative Spectroscopic and Electrochemical Study of V(V)-Substituted Keggin-Type Phosphomolybdates and -Tungstates

Vanadium-substituted Keggin-type heteropolyanions have been studied for a wide variety of applications, ranging from catalysis to antiviral/antimicrobial agents. While the V-substituted phosphomolybdates [PVxMo12−xO40](3+x)− have been well investigated in this context, comparatively little is known about the corresponding phosphotungstates [PVxW12-xO40](3+x)−. We have succeeded in synthesizing the sodium salts of the whole series [PVxW12−xO40](3+x)−, for x = 1 to 6, and characterised them spectroscopically (FT-IR, UV-Vis, 31P-, and 51V-NMR) and electrochemically (CV and SWV). Thereby, direct comparisons between the vanadium-substituted phosphomolybdates and -tungstates, with substitution degrees from 1 to 6, can be established, which provides a solid basis for further investigations of potential applications.

Simple Approach toward N-Heterocyclic Carbene-Protected Gold Nanoclusters

Little advance has been made toward developing alternative bottom-up synthetic strategies for N-heterocyclic carbene (NHC)-stabilized gold nanoclusters, although this unique class of nanomaterials has exhibited exciting properties. We report in this work a simple and straightforward approach toward NHC-ligated gold nanoclusters by using imidazolium salts rather than free carbenes or NHC-coordinated gold complexes (NHC-Au-X, X is counterions) as precursors. Illustrated here is a one-pot and one-step preparation of an NHC-stabilized Au₁₃Br₄ cluster that features a distinct molecular formula, surface motifs, and assembling modes via chemical reduction of dpaAu, NaOMe, and ^FNHC^Bn·HBr by NaBH₄ (Hdpa is dipyridylamine; ^FNHC^Bn·HBr is 1,3-dibenzyl-5,6-difluoro-1H-benzo[d]imidazole-3-ium bromide). In situ UV-vis and NMR studies have elucidated the base-assisted formation of NHCs from imidazolium salts for the protection of the metal core. This work not only reports a new NHC-ligated superatom that completes the Au₁₃ library, thus facilitating structure-property studies, but also opens the door to explore underlying analogues in a facile and reasonable way.

Preparation, photoluminescence and excited state properties of the homoleptic cluster cation [(W6I8)(CH3CN)6]4

Solvated tungsten iodide cluster compounds are presented with the homoleptic cluster cation [(W₆I₈)(CH₃CN)₆]⁴⁺ and the heteroleptic [(W₆I₈)I(CH₃CN)₅]³⁺, synthesized from W₆I₂₂ in acetonitrile. Crystal structures were solved and refined on deep red single-crystals of [(W₆I₈)(CH₃CN)₆](I₃)(BF₄)₃·H₂O, [(W₆I₈)I(CH₃CN)₅](I₃)₂(BF₄), and on a yellow single-crystal of [W₆I₈(CH₃CN)₆](BF₄)₄·2(CH₃CN) on the basis of X-ray diffraction data. The structure of the homoleptic [(W₆I₈)(CH₃CN)₆]⁴⁺ cluster is based on the octahedral [W₆I₈]⁴⁺ tungsten iodide cluster core, coordinated by six apical acetonitrile ligands. The electron localisation function of [(W₆I₈)(CH₃CN)₆]⁴⁺ is calculated and solid-state photoluminescence and its temperature depedence are reported. Additionally, photoluminescence and transient absorption measurements in acetonitrile are shown. Results of the obtained data are compared to compounds containing [(M₆I₈)I₆]^2- and [(M₆I₈)L₆]^2- (M = Mo or W; L = ligand) clusters.

Towards hydrogen-rich ionic (NH4)(BH3NH2BH2NH2BH3) and related molecular NH3BH2NH2BH2NH2BH3

Attempts of the synthesis of ionic (NH₄)(BH₃NH₂BH₂NH₂BH₃) via a metathetical approach resulted in a mixture of the target compound and partly dehydrogenated molecular NH₃BH₂NH₂BH₂NH₂BH₃ product. The mixed specimen was characterised by NMR and vibrational spectroscopies, and the cocrystal structure was analyzed from powder X-ray diffraction data supported by theoretical density functional theory calculations. The compound crystallises in a P2₁/c unit cell with the lattice parameters of a = 13.401(11) Å, b = 13.196(8) Å, c = 17.828(12) Å, β = 128.83(4)°, V = 2556(3) ų and Z = 16. Despite their impressive hydrogen content, similar to ammonia borane, both title compounds release hydrogen substantially polluted with borazine and traces of ammonia and diborane.

A set of closely related methyltransferases for site-specific tailoring of anthraquinone pigments

Modification of the polyketide anthraquinone AQ-256 in the entomopathogenic Photorhabdus luminescens involves several O-methylations, but the biosynthetic gene cluster antA-I lacks corresponding tailoring enzymes. We here describe the identification of five putative, highly homologous O-methyltransferases encoded in the genome of P. luminescens. Activity assays in vitro and deletion experiments in vivo revealed that three of them account for anthraquinone tailoring by producing three monomethylated and two dimethylated species of AQ-256. X-ray structures of all five enzymes indicate high structural and mechanistic similarity. As confirmed by structure-based mutagenesis, a conserved histidine at the active site likely functions as a general base for substrate deprotonation and subsequent methyl transfer in all enzymes. Eight complex structures with AQ-256 as well as mono- and dimethylated derivatives confirm the substrate specificity patterns found in vitro and visualize how single amino acid differences in the active-site pockets impact substrate orientation and govern site-specific methylation.

[6-(Thiophen-2-yl)-2,2′-bipyridine]bis(triphenylphosphine) Copper(I) Tetrafluoroborate

The novel heteroleptic copper (I) complex [6-(thiophen-2-yl)-2,2′-bipyridine]bis(triphenylphosphine) copper(I) tetrafluoroborate (1), formulated as [CuL(PPh3)2]BF4, was synthesized in two steps, utilizing the diimine type ligand L = 6-(thiophen-2-yl)-2,2′-bipyridine and triphenylphosphine (PPh3). The compound was characterized both in the solid state and in solution by employing single crystal X-ray diffraction, IR, UV, and NMR spectroscopies. The complex is an orange emitter that demonstrates a photoluminescence quantum yield of 2.6% in the solid state.

The perfluoroadamantoxy aluminate as an ideal weakly coordinating anion? - synthesis and first applications

Weakly coordinating anions (WCAs) facilitate the stabilization and isolation of highly reactive and almost "naked" cations. Alkoxyaluminate-based WCAs such as [Al(OC(CF₃)₃)₄]^- ([pf]^-) are widely used due to their synthetic accessibility and their high stability. However, small cations are still able to coordinate the oxygen atoms of the [pf]^- anion or even to abstract an alkoxy ligand. The novel WCA [Al(OC₁₀F₁₅)₄]^- ([pfAd]^-; OC₁₀F₁₅ = perfluoro-1-adamantoxy) is characterized by a very rigid core framework, thus indicating a higher stability towards fluoride-ion abstraction (DFT calculations) and providing hope to generate less disordered crystal structures. The [pfAd]^- anion was generated by the reaction of the highly acidic alcohol perfluoro-1-adamantanol C₁₀F₁₅OH with LiAlH₄ in o-DFB. Li[pfAd] could not be synthesized free of impurities (and still contains unreacted alcohol). Yet, starting from contaminated Li[pfAd], the very useful pure salts Ag[pfAd], [Ph₃C][pfAd] and [H(OEt₂)₂][pfAd] could be synthesized. The salts were characterized by NMR spectroscopy, single-crystal X-ray diffraction and IR spectroscopy. Additionally, [NO][pfAd] could be synthesized containing alcohol impurities but nonetheless enabled the synthesis of the salt P₉⁺[pfAd]^-. The synthesis of Tl[pfAd] in a mixture of H₂O/acetone/o-DFB demonstrated the water stability of the [pfAd]^- anion.

Chiral copper-hydride nanoclusters: synthesis, structure, and assembly

An effective strategy is developed to synthesize a novel and stable layered Cu nanocluster using a one-pot reduction method. The cluster, with a molecular formula of [Cu₁₄(^tBuS)₃(PPh₃)₇H₁₀]BF₄ which has been unambiguously characterized by single crystal X-ray diffraction analysis, exhibits different structures from previously reported analogues with core-shell geometries. In the absence of chiral ligands, the cluster displays intrinsic chirality owing to the non-covalent ligand-ligand interactions (e.g., C-H⋯Cu interactions and C-H⋯π interactions) to lock the central copper core. The interlacing of chiral-cluster enantiomers forms a large cavity, which lays the foundation for a series of potential applications such as drug filling and gas adsorption. Moreover, the C-H⋯H-C interactions of phenyl groups between different cluster moieties promote the formation of a dextral helix and realization of the self-assembly of nanostructures.

Anticooperativity and Competition in Some Cocrystals Featuring Iodine-Nitrogen Halogen Bonds

Phenomena such as anticooperativity and competition among non-covalent bond donors and acceptors are key considerations when exploring the polymorphic and stoichiomorphic landscapes of binary and higher-order cocrystalline architectures. We describe the preparation of four cocrystals of 1,3,5-trifluoro-2,4,6-triiodobenzene with N-heterocyclic compounds, namely acridine, 3-aminopyridine, 4-methylaminopyridine, and 1,2-di(4-pyridyl)ethane. The cocrystals, which are characterized by single-crystal and powder X-ray diffraction experiments, all show moderately strong and directional iodine⋅⋅⋅nitrogen halogen bonds with reduced distance parameters ranging from 0.79 to 0.92 and carbon-iodine⋅⋅⋅nitrogen bond angles ranging from 165.4(3) to 175.31(7)°. The cocrystal comprising 1,3,5-trifluoro-2,4,6-triiodobenzene and acridine provides a relatively rare example where all three halogen bond donor sites form halogen bonds with three acceptor molecules, overcoming an anticooperative effect. This effect manifests itself through the lengthening of non-halogen-bonded C-I bonds, weakening their potential to form halogen bonds. The effect is only observed once two halogen bonds have been formed to 1,3,5-trifluoro-2,4,6-triiodobenzene; one such bond does not appear to be adequate. Among the four cocrystals studied, competition between the pyridyl nitrogen atoms and the amine nitrogen atoms suggests that the former are the preferred halogen bond acceptors. Analysis by Hirshfeld fingerprint plots and ¹³ C and ¹⁹ F magic-angle spinning solid-state nuclear magnetic resonance (NMR) spectroscopy provides additional insights into the prevalence of various short contacts in the crystal structures and into the spectral response to halogen-bond-induced cocrystallization.

Coordination and Stabilization of a Lithium Ion with a Silylene

Herein, we report the stabilization of lithium-ion as the source of lithium to use as a trans-metalation reagent [{PhC(N^t Bu)₂ Si(^t Bu)Li}₂ I(^t BuN)₂ CPh] (1). The reaction of 3 equivalents of the LSi^t Bu (L=PhC(N^t Bu)₂ ) and lithium iodide at low temperature leads to a silylene stabilized lithium-ion with an additional coordination of amidinate ligand. Compound 1 shows two four membered and one six membered ring as confirmed by QTAIM calculations. Whereas the reaction of the LSiCl with 1.5 equivalents of carbodiimide (CyN)₂ C at room temperature affords compound [PhC(N^t Bu)₂ Si(Cl)(NCy)₂ NCy] (2) with the CN₂ SiN₂ C skeleton containing silicon as a central atom. Both the compounds were fully characterized by NMR, mass spectrometry, X-ray crystallographic analysis, and quantum mechanical calculations.

A Molybdenum(VI) Complex of 5-(2-pyridyl-1-oxide)tetrazole: Synthesis, Structure, and Transformation into a MoO3-Based Hybrid Catalyst for the Epoxidation of Bio-Olefins

The discovery of heterogeneous catalysts synthesized in easy, sustainable ways for the valorization of olefins derived from renewable biomass is attractive from environmental, sustainability, and economic viewpoints. Here, an organic–inorganic hybrid catalyst formulated as [MoO3(Hpto)]·H2O (2), where Hpto = 5-(2-pyridyl-1-oxide)tetrazole, was prepared by a hydrolysis–condensation reaction of the complex [MoO2Cl2(Hpto)]∙THF (1). The characterization of 1 and 2 by FT-IR and Raman spectroscopies, as well as 13C solid-state NMR, suggests that the bidentate N,O-coordination of Hpto in 1 (forming a six-membered chelate ring, confirmed by X-ray crystallography) is maintained in 2, with the ligand coordinated to a molybdenum oxide substructure. Catalytic studies suggested that 2 is a rare case of a molybdenum oxide/organic hybrid that acts as a stable solid catalyst for olefin epoxidation with tert-butyl hydroperoxide. The catalyst was effective for converting biobased olefins, namely fatty acid methyl esters (methyl oleate, methyl linoleate, methyl linolenate, and methyl ricinoleate) and the terpene limonene, leading predominantly to the corresponding epoxide products with yields in the range of 85–100% after 24 h at 70 °C. The versatility of catalyst 2 was shown by its effectiveness for the oxidation of sulfides into sulfoxides and sulfones, at 35 °C (quantitative yield of sulfoxide plus sulfone, at 24 h; sulfone yields in the range of 77–86%). To the best of our knowledge, 2 is the first molybdenum catalyst reported for methyl linolenate epoxidation, and the first of the family [MoO3(L)x] studied for methyl ricinoleate epoxidation.

Structure and spectroscopic properties of etherates of the beryllium halides

The synthesis of beryllium halide etherates and the solution behavior in benzene, dichloromethane, and chloroform was studied by NMR, IR, and Raman spectroscopy. Mononuclear units of [BeX 2(L)2] (X = Cl, Br, I; L = Et2O, thf) were identified as the favorably formed species in solution. Treatment of the mononuclear diethyl ether beryllium halide adduct with one equivalent beryllium halide formed the dinuclear compounds [BeX 2(OEt2)]2 (X = Cl, Br, I). The solid-state structures of [BeCl2(thf)2] and [BeBr2(thf)2] have been determined by single crystal X-ray diffraction analysis. [BeI2(thf)2] decomposed in all solvents. In CD2Cl2 the salt [Be(thf)4]I2 was formed, whereas in C6D6 and CDCl3, BeI2 precipitated and [BeI(thf)3]+, [Be(thf)4]2+ together with the thf ring-opening product [Be(μ 2-O(CH2)4I)I(thf)]2 were observed in solution.

Tuning the nuclearity of [Mo2O2S2]2+-based assemblies by playing with the degree of flexibility of bis-thiosemicarbazone ligands

[MoV2O₂S₂]²⁺-based thiosemicarbazone complexes appear as very promising molecules for biological applications due to the intrinsic properties of their components. This paper deals with the synthesis and characterization of six coordination complexes obtained by the reaction of [MoV2O₂S₂]²⁺ clusters with bis-thiosemicarbazone ligands that contain flexible or rigid spacers between the two thiosemicarbazone units. Interestingly, structural characterization by single-crystal X-ray diffraction, MALDI-TOF MS technique and NMR spectroscopy revealed that the nuclearity of the complex is controlled by the nature of the spacer between the thiosemicarbazone units. Binuclear complexes, namely [MoV2O₂S₂(L^1-3)], are isolated with flexible spacers while tetranuclear complexes [(MoV2O₂S₂)₂(L^4-6)₂] are formed when the bis-thiosemicarbazone ligands are built on rigid spacers.

Flexible Aliphatic Diammonioacetates as Zwitterionic Ligands in UO22+ Complexes: Diverse Topologies and Interpenetrated Structures

N,N,N',N'-Tetramethylethane-1,2-diammonioacetate (L1) and N,N,N',N'-tetramethylpropane-1,3-diammonioacetate (L2) are two flexible zwitterionic dicarboxylates which have been used as ligands for the uranyl ion, 12 complexes having been obtained from their coupling to diverse anions, mostly anionic polycarboxylates, or oxo, hydroxo and chlorido donors. The protonated zwitterion is a simple counterion in [H₂L1][UO₂(2,6-pydc)₂] (1), where 2,6-pydc^2- is 2,6-pyridinedicarboxylate, but it is deprotonated and coordinated in all the other complexes. [(UO₂)₂(L2)(2,4-pydcH)₄] (2), where 2,4-pydc^2- is 2,4-pyridinedicarboxylate, is a discrete, binuclear complex due to the terminal nature of the partially deprotonated anionic ligands. [(UO₂)₂(L1)(ipht)₂]·4H₂O (3) and [(UO₂)₂(L1)(pda)₂] (4), where ipht^2- and pda^2- are isophthalate and 1,4-phenylenediacetate, are monoperiodic coordination polymers in which central L1 bridges connect two lateral strands. Oxalate anions (ox^2-) generated in situ give [(UO₂)₂(L1)(ox)₂] (5) a diperiodic network with the hcb topology. [(UO₂)₂(L2)(ipht)₂]·H₂O (6) differs from 3 in being a diperiodic network with the V₂O₅ topological type. [(UO₂)₂(L1)(2,5-pydc)₂]·4H₂O (7), where 2,5-pydc^2- is 2,5-pyridinedicarboxylate, is a hcb network with a square-wave profile, while [(UO₂)₂(L1)(dnhpa)₂] (8), where dnhpa^2- is 3,5-dinitro-2-hydroxyphenoxyacetate, formed in situ from 1,2-phenylenedioxydiacetic acid, has the same topology but a strongly corrugated shape leading to interdigitation of layers. (2R,3R,4S,5S)-Tetrahydrofurantetracarboxylic acid (thftcH₄) is only partially deprotonated in [(UO₂)₃(L1)(thftcH)₂(H₂O)] (9), which crystallizes as a diperiodic polymer with the fes topology. [(UO₂)₂Cl₂(L1)₃][(UO₂Cl₃)₂(L1)] (10) is an ionic compound in which discrete, binuclear anions cross the cells of the cationic hcb network. 2,5-Thiophenediacetate (tdc^2-) is peculiar in promoting self-sorting of the ligands in the ionic complex [(UO₂)₅(L1)₇(tdc)(H₂O)][(UO₂)₂(tdc)₃]₄·CH₃CN·12H₂O (11), which is the first example of heterointerpenetration in uranyl chemistry, involving a triperiodic, cationic framework and diperiodic, anionic hcb networks. Finally, [(UO₂)₇(O)₃(OH)_4.3Cl_2.7(L2)₂]Cl·7H₂O (12) crystallizes as a 2-fold interpenetrated, triperiodic framework in which chlorouranate undulating monoperiodic subunits are bridged by the L2 ligands. Complexes 1, 2, 3, and 7 are emissive with photoluminescence quantum yields in the range of 8-24%, and their solid-state emission spectra show the usual dependence on number and nature of donor atoms.

The Radical Anion and Dianion of Benzo[3,4]cyclobuta[1,2-b]phenazine

We present the reduction of two azaacenes (a benzo-[3,4]cyclobuta[1,2-b]phenazine and a benzo[3,4]cyclobuta[1,2-b]naphtho[2,3-i]phenazine derivative), featuring a single cyclobutadiene unit, to their radical anions and dianions. The reduced species were produced using potassium naphthalenide in the presence of 18-crown-6 in THF. Crystal structures of the reduced representatives were obtained and their optoelectronic properties evaluated. Charging these 4n Hückel systems gives dianionic 4n + 2 π-electron systems with increased antiaromaticity, according to NICS(1.7)_zz calculations, featuring unusually red-shifted absorption spectra.