Single-crystal X-ray Diffraction Analysis Research Articles

Solvent and additive-controlled supramolecular isomerism in zinc coordination polymers

AbstractA new series of Zn(II) supramolecular isomers containing ditopic 1,3-di(pyridin-4-yl)urea (4bpu) ligand were synthesized and characterized by infrared analysis, elemental analysis and TGA as well as single-crystal X-ray diffraction analysis. Four solvent-induced pseudopolymorphic zinc (II) coordination polymers (CPs), namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1), {[Zn(4bpu)(OAc)2](C2H5OH)}n (2), {[Zn(4bpu)(OAc)2](HOCH2CH2OH)}n (3), and {[Zn(4bpu)(OAc)2](0.5H2O)}n (4), were prepared by the reaction of Zn(OAc)2.2H2O and 4bpu via self-assembly under varying solvent systems. Also, a pair of polymorphic coordination polymers namely, {[Zn(4bpu)(OAc)2](CH3OH)}n (1α) and {[Zn3(4bpu)3(OAc)6](CH3OH)2}n(1β), was prepared in the presence of different organic additives. Single-crystal X-ray diffraction confirmed that 1−4 and 1α display 1D polymeric zig-zag chains and 1β exhibits 1D triple-stranded ladders that were self-assembled through various supramolecular interactions. In addition, a series of dissolution-recrystallization structural transformations (DRST) were performed on these supramolecular isomers.

Synthesis, Crystal Structure, Spectroscopic Characterization, In Vitro and In Silico Molecular Docking Studies of Benzyl Tetrazole-N-Isobutyl Acetamide Hybrid

Background: Tetrazole-based compounds are of significant interest due to their potential pharmacological applications. The current study focuses on the synthesis and analysis of such a compound. Objective: This research aims to synthesize the title compound N-(3-methyl-1-phenyl-2-(1Htetrazol- 1-yl) butyl) acetamide, analyze its crystal structure, perform computational studies, and evaluate its potential pharmacological activities and it’s in silico and in vitro supports, specifically antidiabetic and anti-inflammatory properties. Methods: The title compound, C14H19N5O, was synthesized, and its crystal structure was confirmed using single-crystal X-ray diffraction analysis by default parameters. Density Functional Theory (DFT) calculations were performed using the Gaussian 09W software package with the B3LYP/6-311++G (d,p) method to optimize the compound's structure and calculate its HOMOLUMO energy gap, Molecular Electrostatic Potential (MEP), and Mulliken charge distribution. In vitro, antidiabetic and anti-inflammatory activities were assessed and compared with standard drugs by using reported protocols. Additionally, molecular docking studies were conducted with enzymes related to diabetes and inflammation with default parameters, and Auto-Dock 4.2 software was used. Results: The X-ray diffraction analysis confirmed the crystal structure, and the Density Functional Theory (DFT) calculations provided insights into the molecular properties of the compound. Molecular docking experiments with relevant enzymes further supported the significant antidiabetic and anti-inflammatory activities demonstrated in the in vitro tests. Conclusion: The synthesized tetrazole-based compound exhibits promising antidiabetic and antiinflammatory activities, supported by both experimental and theoretical studies, suggesting its potential for further pharmacological investigation.

Osmaborane Clusters with B4 and B5 Rings Stabilized in the Coordination Sphere of {OsLn} (Ln = η5-C5Me5 or H2(PPh3)2).

New synthetic routes have been developed to synthesize osmaborane clusters featuring B4 and B5 rings in the coordination spheres of osmium. Thermolysis of [Os(PPh3)3Cl2], 1 in the presence of excess of [BH3·THF] led to the formation of [Os(PPh3)2H2(η4-B4H8)], 2 along with [HOs(PPh3)2B5H10], 3. Cluster 2 features a planar tetraborane ring coordinated to an osmium center in an η4 fashion. Cluster 3 can be considered an osmium analogue of hexaborane(10), in which the osmium center is situated at the base of the pentagonal pyramid geometry. In a different synthetic protocol, we have carried out the metathesis reaction of [Cp*OsBr2]2 (Cp* = η5-pentamethylcyclopentadienyl), 5 with [LiBH4·THF] followed by thermolysis in the presence of [BH3·THF] that generated [Cp*Os(η5-B5H10)], 6. Cluster 6 has a planar pentaborane ring that is stabilized in the coordination sphere of osmium, making it a boron analogue of osmocene. Clusters 2 and 6 are the first examples of structurally characterized planar B4 and B5 rings, respectively, that are stabilized in the coordination sphere of osmium. All the synthesized molecules were characterized using multinuclear NMR and IR spectroscopy, mass spectrometry, and single crystal X-ray diffraction analyses. Theoretical calculations were carried out to visualize the electronic structures and bonding scenarios in 2 and 6.

Bismuth Bound to Transition Metals: Visible-Light-Induced Olefin Coordination, Reductive Elimination, and Oxidative Addition.

A series of dibenzobismepinyl (C14H10Bi) substituted transition metal complexes of the type [(C14H10Bi)M(CO)x(L)] (M = Mn, Co, Fe) was prepared in salt elimination reactions from a halobismepine and sodium metallates. Irradiation of these complexes with visible light has been investigated, aiming at the elimination of one carbonyl ligand and the concomitant coordination of the bismepine's olefin moiety to the transition metal center. The resulting complexes of the type [{κ2C,κ1Bi-(C14H10)Bi}M(CO)x-1(L)] (M = Co, Fe) have been isolated and fully characterized. When two dibenzobismepinyl units are positioned in the coordination sphere of an iron carbonyl complex fragment, reductive elimination / oxidative addition events of the dibismuthane (C14H10Bi)2 have been shown to be relevant. The analytical techniques applied in this work include (heteronuclear) NMR spectroscopy, elemental analysis, single-crystal X-ray diffraction analysis, UV/Vis spectroscopy, IR spectroscopy and (TD)-DFT calculations.

Enzyme (α-Glucosidase, α-Amylase, PTP1B & VEGFR-2) Inhibition and Cytotoxicity of Fluorinated Benzenesulfonic Ester Derivatives of the 5-Substituted 2-Hydroxy-3-nitroacetophenones

The prevalence of small multi-target drugs containing a fluorinated aromatic moiety among approved drugs in the market is due to the unique properties of this halogen atom. With the aim to develop potent antidiabetic agents, a series of phenylsulfonic esters based on the conjugation of the 5-substituted 2-hydroxy-3-nitroacetophenones 1a–d with phenylsulfonyl chloride derivatives substituted with a fluorine atom or fluorine-containing (-CF3 or -OCF3) group were prepared. Their structures were characterized using a combination of spectroscopic techniques complemented with a single-crystal X-ray diffraction (XRD) analysis on a representative example. The compounds were, in turn, assayed for inhibitory effect against α-glucosidase, α-amylase, protein tyrosine phosphatase 1 B (PTP1B) and the vascular endothelial growth factor receptor-2 (VEGFR-2) all of which are associated with the pathogenesis and progression of type 2 diabetes mellitus (T2DM). The antigrowth effect of selected compounds was evaluated on the human breast (MCF-7) and lung (A549) cancer cell lines. The compounds were also evaluated for cytotoxicity against the African Green Monkey kidney (Vero) cell line. The results of an in vitro enzymatic study were augmented by molecular docking (in silico) analysis. Their ADME (absorption, distribution, metabolism and excretion) properties have been evaluated on the most active compounds against α-glucosidase and/or α-amylase to predict their drug likeness.

Impurities in Arylboronic Esters Induce Persistent Afterglow.

Several recent reports suggest that arylboronic esters can exhibit room temperature phosphorescence (RTP), an optical property that is desirable for applications in security printing, oxygen sensing, and bioimaging. These findings challenged the fundamental notion that heavy elements or changes in orbital symmetry were required for intersystem crossing to occur in organic compounds. As we had not observed long afterglow in the many arylboronic esters we had synthesized over many years, we suspected that the RTP observed in these systems had a simpler explanation: the materials reported were impure. Herein, we synthesized 12 arylboronic esters that were previously reported to show RTP, and carefully purified them by column chromatography, recrystallization, and sublimation. We re-examined their photophysical properties alongside single-crystal X-ray diffraction analysis and detailed theoretical studies. While 4 of the 12 compounds showed long afterglows as crude products, none of them showed persistent RTP after careful purification. We also successfully isolated the impurity 4-amino-3,5-bis(pinacolatoboryl)benzonitrile (2), identifying it as the impurity responsible for inducing delayed fluorescence in 3,5-bis(pinacolatoboryl)benzonitrile (1). Doping 1 with 1.0 mol % 2 led to a persistent afterglow with a lifetime of 67 ms, which is mediated by a dimer charge transfer state. Our findings call for a re-examination of previous studies reporting RTP from arylboronic esters, highlight the importance of careful purification in photophysical research, and provide a practical strategy for designing organic materials with a long afterglow.

Synthesis, characterization and magnetic properties of a hexanuclear copper (II) complex with hydroxido, alkoxido and phenoxido bridges

A new CuII6 complex, formulated as [Cu6(L)3(µ3-OH)(H2O)(OH)(NO3)]·2H2O(1) has been prepared using the symmetrical N2O3-donor Schiff-base ligand H3L = N,N′-(2-hydroxypropane-1,3-diyl)bis(2-hydroxyacetophenimine). Compound 1 has been structurally and spectroscopically characterized. Single crystal X-ray diffraction analysis reveals that 1 crystallizes in the triclinic space group P-1 and consists of a CuII6 complex where each deprotonated ligand chelates two CuII centres. Three of the six independent CuII centres are arranged in an almost equilateral triangle with double Cu-O-Cu bridges, formed by a μ3-hydroxido and phenoxido bridges. Each of the three CuII centres in the triangle is further connected to one CuII centre through a single alkoxido bridge. The magnetic properties indicate the presence of moderate and weak antiferromagnetic interactions through the double and single oxido bridges, respectively.

Half-Sandwich Cerium and Lanthanum Dialkyl Complexes: Synthesis, Structure, and Reactivity Studies.

Cerium and lanthanum dialkyl complexes [η5-1,2,4-(Me3C)3C5H2]Ln(CH2C6H4-o-NMe2)2 (Ln = Ce 1 and La 2), supported by a tri-tert-butylcyclopentadienyl ligand, have been successfully synthesized. Studies demonstrate that these complexes possess diverse reactivity toward various small molecules. For example, the reaction of complexes 1 and 2 with diphenyl dichalcogenides PhEEPh (E = S, Se) results in the formation of lanthanide thiolates [(η5-1,2,4-(Me3C)3C5H2)Ln(SPh)(μ-SPh)]2 (Ln = Ce 3 and La 4) and selenolates [(η5-1,2,4-(Me3C)3C5H2)Ln(SePh)(μ-SePh)]2 (Ln = Ce 5 and La 6), concomitantly releasing PhE(CH2C6H4-o-NMe2). Furthermore, complexes 1 and 2, upon reaction with dibenzyl disulfide, yield tetranuclear rare-earth metallomacrocyclic compounds {[(η5-1,2,4-(Me3C)3C5H2)Ln(μ-SCH2C6H5)]2(μ-η3:η3-SCHC6H5)}2 (Ln = Ce 7 and La 8). This reaction may involve a process of σ-bond metathesis and C-H activation. While the reaction of 1 and 2 with dibenzyl diselenide in the presence of LiCH2C6H4-o-NMe2 leads to the formation of lanthanide-lithium selenido clusters [(η5-1,2,4-(Me3C)3C5H2)La(μ-SeCH2C6H5)]3(μ3-Se)[μ3-SeLi(THF)3] (Ln = Ce 9 and La 10). Meanwhile, lanthanide selenido clusters [(η5-1,2,4-(Me3C)3C5H2)La(μ-SeCH2C6H4-o-NMe2)]4(μ3-Se)2 (Ln = Ce 11 and La 12) can be obtained by treating 1 and 2 with elemental selenium in a 1:2 molar ratio. Additionally, the treatment of 1 and 2 with benzoxazole generates ring-opening/C-C coupling/C-N coupling products {(η5-1,2,4-(Me3C)3C5H2)La[μ-OC6H4-o-N═CHN(CH(CH2C6H4-o-NMe2)2C6H4-o-O]}2 (Ln = Ce 13 and La 14). All new compounds were characterized by various spectroscopic methods, and their solid-state structures were confirmed by single-crystal X-ray diffraction analyses.

Bridge-Dependent Donor-Metal-Acceptor-Metal-Donor (D-M-A-M-D) Systems: From Charge Transfer to Electron Transfer in Dioxolene-Ge-Diimine Complexes.

Synthesis and structural characterization of a family of germanium-dioxolene complexes with ditopic N-donor ligands (L1-L5) (L1=1,2-bis(pyridin-2-ylmethylene)hydrazine L2=1,6-bis-(pyridin-2-yl)-2,5-diaza-1,5-hexadiene, L3=N,N-bis(pyridin-2-ylmethylene)-1,4-benzenediamine, L4=N,N-bis(pyridin-2-ylmethylene)-(biphenyl)-4,4-diamine, L5=2,2'-azopyridine) is reported. The reaction of germanium bis-catecholate with bridging ligands L1 - L4, differing by the nature of the linker between pyridine sites gives rise to dinuclear digermanium complexes (36Cat2Ge)2L1-4 (36Cat=dianion of 3,6-di-tert-butylcatechol) 1-4 of DMAMD type (donor-metal-acceptor-metal-donor) with a charge transfer in the UV-Vis region. In opposite, the interaction of the 36Cat2Ge with 2,2'-azopyridine (L5) results in the two-electron transfer from the donor 36Cat2- ligands to the azopyridine bridge forming stable open-shell complex 5 [(36SQ)(36CatGe)]2(L5)2- (36SQ=radical-anionic semiquinonate ligand). Molecular structures of compounds 3 and 5 were determined by single crystal X-ray diffraction analysis. Electronic structures of complexes 1-5 were studied by means of DFT calculations.

Bowl-Shaped Anthracene-Fused Antiaromatic Ni(II) Norcorrole: Synthesis, Structure, Assembly with C60, and Photothermal Conversion.

The synthesis of bowl-shaped antiaromatic molecules represents a formidable challenge, because the molecular distortion further destabilizes these already inherently reactive molecules. Here, we report the synthesis and properties of bowl-shaped fused anthrylnorcorroles that exhibit near-infrared (NIR) absorption reaching 1900 nm. The oxidation of meso-anthryldibromodipyrrin provides fused anthryldibromodipyrrin, which was converted to the fused mono- and bisanthrylnorcorroles through Ni(0)-mediated intramolecular coupling with a bis(dibromodipyrrin) Ni(II) complex. Single-crystal X-ray diffraction analyses revealed bowl-shaped structures for the fused mono- and bisanthrylnorcorroles, which enables them to act as suitable receptors for C60 with bonding constants of 2.89 × 103 M-1 and 1.59 × 103 M-1, respectively. The formation of a 1:1 complex between the fused monoanthrylnorcorrole and C60 was confirmed by single-crystal X-ray diffraction analysis. The effective expansion of the π-conjugation through the triple fusion of the norcorrole with the anthracene units substantially enhances the near-infrared absorption bands, which endows these anthrylnorcorroles with effective photothermal conversion.

Encasing Triaryltriazine with a Bulky Chiral Cap: Luminescent Chiral Crystalline Molecular Rotors with Modulation of Solid-State Chiroptical Properties Mediated by Molecular Rotation.

A novel structural motif for luminescent chiral crystalline molecular rotors with chiroptical properties correlated with the rotational motion in crystalline media is presented. This scaffold incorporates bulky chiral caps consisting of a homochiral binaphthyl moiety with a triisopropylsilyl (TIPS) group into triaryltriazine, as confirmed by single-crystal X-ray diffraction (XRD) analysis. Variable-temperature solid-state 2H NMR studies revealed a 4-fold rotation of the phenylenes occurred in the rotor crystal between 263 and 333 K, while a steric rotor analogue shows no rotational motion. Notably, a reduction in the dihedral angle of the binaphthyl moiety upon heating was observed in the chiral rotors, and a corresponding alteration of the circular dichroism (CD) signal was detected in the solid-state, while those of the steric rotors showed no alteration by the temperature change. We propose that the fast rotation of the phenyl rings affects the motion of neighboring isopropyl groups, leading to steric repulsion with the binaphthyl moieties and thereby inducing its conformational change. Furthermore, the chiral rotors exhibited circularly polarized phosphorescence in the solid-state at low temperature, originating from rotational displacement of the phenylene on triphenyltriazine during structural relaxation in the excited state. Meanwhile, the steric rotors showed significant circularly polarized fluorescence induced by the suppressed molecular motion via a sterically hindered lattice environment in the excited state. These results indicate that the bulky chiral cap introduced into the triaryltriazines, acting as a luminescent chiral crystalline molecular rotor, can be a useful scaffold for the modulation of solid-state chiroptical properties via molecular rotational motions.

Discovery of ent-kaurane diterpenoid glucosides as potent analgesics from the leaves of Pieris formosa

To search for structurally novel analgesics from Ericaceae plants, the leaves of Pieris formosa collected at Yichang, Hubei, China, were phytochemically investigated for the first time. A total of fifteen ent-kaurane diterpene glucosides (1–15) including twelve new ones, named forminosides A–L (1–12), were isolated. Their structures were elucidated by comprehensive spectroscopic data analyses, quantum chemical calculations (13C NMR and ECD calculations and DP4+ analysis), and chemical methods. The absolute configures of 1–3, 5–8, 11, and 13 were further determined by single-crystal X-ray diffraction analysis. Forminoside A (1) represents the first 3α-(β-d-glucopyranosyloxy)-11,16-epoxy-ent-kaurane diterpenoid bearing a unique 12-oxa-pentacyclo[9.3.3.01,10.04,9.013,16]heptadecane core. Forminoside J (10) is the first 17-nor-ent-kaurane type diterpenoid from Ericaceae family, while forminoside L (12) represents the first example of 4,5-seco-ent-kaurane diterpenoid glycoside bearing an unusual α-hydroxyl-α,β-unsaturated ketone block. Notably, the structure of mollisside A was revised to 3β-(β-d-glucopyranosyloxy)-16β,17-dihydroxy-ent-kaurane based on the NMR and single-crystal X-ray diffraction data analysis of forminoside C (3). All the isolates 1–15 showed potent analgesic activity in the HOAc-induced writhing test in mice. Among them, compounds 1–3, 5–12, and 15 exhibited significant analgesic effects at a dose of 5.0 mg/kg with the inhibition rates over 50%. Compounds 1, 5, 7, and 9–12 still displayed significant analgesic effects with the inhibition rates exceeding 50% at a lower dose of 1.0 mg/kg. Forminosides J (10) and L (12) still showed significant analgesic potency even at a lower dose of 0.2 mg/kg, comparable to that of the positive control, morphine. This is first report of the analgesic activity of 11,16-epoxy-ent-kaurane diterpenoid. A preliminary structure–activity relationship was explored, providing new clues to design novel analgesics based on the ent-kaurane and related diterpenoids.

Four Tremulanes and Two Pyroglutamate-Containing Dipeptides from the Mangrove Endophytic Fungus Phaeosphaeriopsis sp. P11.

Four new tremulane sesquiterpenes, named phaeosphaerienols A-D (1-4), and two new pyroglutamate-containing dipeptides, named phaeosphaeratides A-B (5-6), were isolated from the mangrove endophytic fungus Phaeosphaeriopsis sp. P11, together with a new 2-furancarboxylic acid derivative (7). Structurally, pheaosphaerienols A-C (1-3) are rare tremulanes containing a 1,10-epoxide moiety. The structures of these compounds were established by extensive NMR spectroscopic data, single-crystal X-ray diffraction analysis, and Marfey's derivatization method. All the isolates were evaluated for their cytotoxic, antibacterial, and DPPH free radical scavenging effects. However, none of the compounds exhibited obvious activities.

Exceptionally Short Tetracoordinated Carbon-Halogen Bonds in Hexafluorodihalocubanes.

Molecules that contain bonds whose length significantly deviates from the average are of interest in the context of understanding the nature and limits of the chemical bonds. However, it is difficult to disentangle the individual contributions of the multiple factors that give rise to such bond-length deviations as reports on such molecules remain scarce. In the present study, we have succeeded in synthesizing hexafluorodihalocubanes of the type C8F6X2 (2) (X = Cl (2Cl), Br (2Br), I (2I)), which represent a new series of molecules with unusual C(sp3)-halogen bonds. The C(sp3)-halogen bonds of 2Cl, 2Br, and 2I, determined via single-crystal X-ray diffraction analysis, are approximately 0.07-0.09 Å shorter than typical C(sp3)-halogen bonds. In particular, the carbon-iodine bonds of 2I are the shortest C(sp3)-I bonds reported to date. The solution-state structures and electronic states of the C(sp3)-halogen bonds in these hexafluorodihalocubanes were analyzed by X-ray absorption spectroscopy, which revealed detailed information on the length of these C(sp3)-halogen bonds in solution and the solid state as well as on the electron-deficient nature of 2. Detailed theoretical calculations and a comparison with halotrinitromethanes (1), which represent another series of molecules with shortened C(sp3)-halogen bonds, revealed that the factors responsible for the shortening of the C(sp3)-halogen bond vary among the different C(sp3)-halogen bonds, i.e., for C(sp3)-Cl and C(sp3)-Br, the s-character and hyperconjugation effects predominate, whereas for C(sp3)-I, the interatomic Coulombic interaction effect prevails.

New Chlorine-Containing Sesquiterpenoid from Artemisia Blepharolepis.

One new chlorinated sesquiterpenoid (compound 1, ablepharolide) and twenty-one known compounds were obtained from the aerial parts of Artemisia blepharolepis. Their structures were established by spectroscopic methods and the absolute configuration was further determined by single-crystal X-ray diffraction analysis for ablepharolide. Ablepharolide is a rare sesquiterpenoid with a 4-methyl-7-isopropyl-9-ethyl-perhydroindene skeleton that incorporates a chlorine atom. It significantly inhibited the growth of MCF-7 cells with IC50 value of 8.34±0.77 μM. Further investigations demonstrated that ablepharolide induced morphological changes in MCF-7 cells, inhibited proliferation in a time- and dose-dependent manner. Furthermore, western blot analysis revealed that ablepharolide induced a significant increase in cleaved caspase-8, cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase (PARP) in MCF-7 cells. All of these results supported that ablepharolide induced exogenous apoptosis in MCF-7 cells.

Dibenzo-peri-Heptacene: A Stable Open-Shell Graphene Fragment With a Balanced Combination of Armchair and Zigzag Edge Structures.

Atomically precise open-shell graphene fragments, such as extended peri-acenes, hold significant interest for electronics and spintronics. However, their inherent high reactivity poses challenges for synthesis and application. In this study, a novel approach is introduced: the fusion of a zigzag-edged peri-tetracene with an all-armchair-edged hexa-peri-hexabenzocoronene (HBC) via two shared benzene rings to produce a stable open-shell hydrocarbon, named dibenzo-peri-heptacene (DBPH). The DBPH derivative 1 exhibits considerably enhanced stability, with a half-life (t1/2) of 46 days in toluene solution under ambient conditions. This improved stability is attributed to peri-benzannulation, enhanced aromatic stabilization, and kinetic protection of the reactive sites along the zigzag edges. The structure of 1 is unequivocally verified through single-crystal X-ray diffraction analysis. With a balanced combination of armchair and zigzag edge structures, derivative 1 displays a diradical character of 39.2% and a singlet-triplet gap of ≈-3.16 kcalmol-1. It features a narrow electrochemical energy gap (0.87 eV) and exhibits amphoteric redox behavior. Notably, its dication and dianion states manifest a closed-shell singlet ground state, representing doubly charged structures where a HBC unit is fused with a benzo[f]tetraphene moiety. This research paves the way for synthesizing novel open-shell graphene fragments with adjustable electronic properties and exceptional stability.

Synthesis, crystal structure, hirshfeld surface analysis, and computational studies of dimeric and polymeric cadmium complexes

In the current investigation, a new dimeric [Cd(DNBA)2(py)2]2 and a polymeric [Cd(DNBA)2(pyz)2]n cadmium complexes have been prepared by the reaction of 3,5-dinitrobenzoic acid (main ligand), nitrogen donor auxiliary ligands (pyridine and pyrazine), and Cd(II) sulphate in aqueous media. The crystal structures of the synthesized compounds were determined by single-crystal X-ray diffraction analysis. The crystal structures were investigated in terms of the coordination geometry, dihedral angles between various rings, and intermolecular interactions. The solid-state assembly was stabilized by various interatomic contacts, explored by Hirshfeld surface analysis. Void analysis was performed to predict the response of crystals to the applied stress. The optimized molecular geometries of the compounds were achieved utilizing the DFT approach along with the B3LYP functional/6–311G(d,p)/LANL2DZ basic set. MEP maps, molecular orbital theory, and quantum chemical parameters for the synthesized compounds were generated using the same level of theory.

A Syndiotactic Polymer via Spontaneous Exoselective Single-Crystal-To-Single-Crystal Topochemical Diels-Alder Cycloaddition Reaction.

We designed and synthesized an amide-based monomer decorated with furan as the diene unit and maleimide as the dienophile unit at its termini. Single-crystal X-ray diffraction (SCXRD) analysis of its crystal revealed a head-to-tail arrangement of molecules with furan and maleimide groups of neighboring molecules proximally placed in an arrangement suitable for their topochemical Diels-Alder cycloaddition (TDAC) to form a linear polymer. The monomer underwent a spontaneous single-crystal-to-single-crystal (SCSC) polymerization at room temperature, yielding a linear polymer with oxa-bicyclic linkage. SCXRD analysis revealed that the cycloaddition occurred in an exoselective manner, and the absolute stereochemistry of the oxa-bicyclic linkage alternated in successive repeat units, leading to a syndiotactic linear polymer. The polymerization can be accelerated by heating the powder at 120 °C; the topochemical nature of the high-temperature reaction was established by time dependent differential scanning calorimetry (DSC), time-dependent powder X-ray diffraction (PXRD), and UV-visible spectroscopic analysis; the polymer was characterized using solid-state NMR spectroscopy and MALDI-TOF mass spectrometry.

Insight into γ-Irradiation-Induced Structure Evolution of Uranium(IV) Germanates as Crystalline Nuclear Waste Forms.

New kinds of crystalline waste forms with improved structural stability are desirable for actinide immobilization. In this work, using a molten salt method, two uranium(IV) germanate compounds, namely, K2UGe3O9 (1) and K2UGe2O7 (2), were synthesized, whose compositions consisted of trimeric and dimeric units of germanate, as well as tetravalent uranium, as proved by bond valence calculation and X-ray absorption spectra. Radiation stability assessment is further performed by γ-irradiation to assess the potential of as-synthesized uranium germanate compounds as nuclear waste forms. Powder X-ray diffraction and single-crystal diffraction analyses reveal that 1 remains stable within 1 MGy dosage and undergoes a significant structural change with increasing dosage at 2 MGy, leading to a transformation of 1 to 1-ir analogous to 2 in chemical structure. The underlying mechanism was further studied through a combination of different characterization techniques, including Raman, UV-vis, and electron paramagnetic resonance spectroscopies. Density functional theory calculations of 1 and 2 were also conducted to probe the coordination interaction of germanium and uranium with oxygen atoms. This work reports new crystalline uranium germanates by flux growth and, most importantly, provides insights into the irradiation stability of these materials, which will be beneficial to developing waste forms for long-term immobilization of radionuclides.

Ent-Abietane-type lactones with anti-inflammatory activity from Euphorbia helioscopia

Euphohelinodes D–I (1–6), six previously unreported ent-abietane lactones, along with two known analogues (7 and 8), were isolated from the anti-inflammatory fraction extracted from E. helioscopia by a bioactivity-guided isolation. Their structures were characterized using a combination of spectroscopic data interpretation, single-crystal X-ray diffraction and ECD analysis. The anti-inflammatory activity of these compounds was evaluated by measuring their inhibitory effects on NO production in LPS-stimulated RAW264.7 macrophages. The most active candidate, euphohelinode H (5), had better inhibitory activity against NO production with an IC50 value of 30.23 ± 2.33 μM. Further study revealed that 5 significantly suppressed the expressions of iNOS and COX-2 through the NF-κB signaling pathway.