Reversible modulation of interlayer stacking in 2D copper-organic frameworks for tailoring porosity and photocatalytic activity.

The properties of two-dimensional covalent organic frameworks (2D COFs), including porosity, catalytic activity as well as electronic and optical properties, are greatly affected by their interlayer stacking structures. However, the precise control of their interlayer stacking mode, especially in a reversible fashion, is a long-standing and challenging pursuit. Herein, we prepare three 2D copper-organic frameworks, namely JNM-n (n = 7, 8, and 9). Interestingly, the reversible interlayer sliding between eclipsed AA stacking (i.e., JNM-7-AA and JNM-8-AA) and staggered ABC stacking (i.e., JNM-7-ABC and JNM-8-ABC) can be achieved through environmental stimulation, which endows reversible encapsulation and release of lipase. Importantly, JNM-7-AA and JNM-8-AA exhibit a broader light absorption range, higher charge-separation efficiency, and higher photocatalytic activity for sensitizing O2 to 1O2 and O2•- than their ABC stacking isostructures. Consequently, JNM-8-AA deliver significantly enhanced photocatalytic activities for oxidative cross-coupling reactions compared to JNM-8-ABC and other reported homogeneous and heterogeneous catalysts.

A Photosensitizing Metal-Organic Framework as a Tandem Reaction Catalyst for Primary Alcohols from Terminal Alkenes and Alkynes.

Owing to the wide and growing demand for primary alcohols, the development of efficient catalysts with high regioselectivity remains a worthwhile pursuit. However, according to Markovnikov's rule, it is a challenge to obtain primary alcohols with high yields and regioselectivity from terminal alkenes or alkynes. Herein, we report the synthesis of a photosensitizing two-dimensional (2D) metal-organic framework (MOF) from cyclic trinuclear copper(I) units (Cu-CTUs) and a boron dipyrro-methene (Bodipy) ligand. The MOF features broadband light absorption, excellent photoinduced charge separation efficiency, and photochemical properties. By integrating the copper-catalyzed hydroboration and photocatalyzed aerobic oxidation, it can catalyze terminal alkenes and alkynes to produce primary alcohols via a one-pot tandem reaction with excellent regioselectivity, good overall yields in two-step reactions (up to 85 %), broad substrate compatibility (32 examples) and good reusability under mild conditions.

Effects of gene silencing of indoleamine 2,3-dioxygenase 1 combined with rosmarinic acid on tumor immune microenvironment in H22 tumor-bearing mice.

Rosmarinic acid (RA) is a natural polyphenolic compound with several pharmacological activities, including immunomodulation and anti-tumor effect. Indoleamine 2,3-dioxygenase-1 (IDO1), the rate-limiting enzyme that metabolizes tryptophan into kynurenine, is an important negative immune regulator. This study aimed to explore the effect of combined action of IDO1 gene silencing and RA on tumor immune microenvironment. H22 tumor-bearing mice were treated with combination therapy with RA and IDO1-shRNA. The percentages and apoptosis of T-cells and subsets of splenic regulatory T-cells (Tregs) were detected by flow cytometry. Levels of tumor necrosis factor (TNF-α), Interferon-γ (IFN-γ), interleukin-2 (IL-2) and interleukin-10 (IL-10) were measured by enzyme linked immunosorbent assay (ELISA). Treatment with RA + IDO1-shRNA significantly increased the percentage of CD4+ T cells, ratio of CD4+/CD8+ and the levels of IFN-γ and IL-2, while decreased CD8+ apoptosis, the proportion of splenic Tregs and the levels of TNF-α and IL-10. The present study demonstrated that combination therapy with RA and IDO1-shRNA had anti-tumor effects on HCC. The mechanism might be related to regulating immune response and immunocytokines, as well as alleviating immunosuppression induced by Tregs in the tumor immune microenvironment.

An Atomically Precise Pyrazolate-Protected Copper Nanocluster Exhibiting Exceptional Stability and Catalytic Activity.

The synthesis of atomically precise copper nanoclusters (Cu-NCs) with high chemical stability is a prerequisite for practical applications, yet still remains a long-standing challenge. Herein, we have prepared a pyrazolate-protected Cu-NC (Cu8), which exhibited exceptional chemical stability either in solid-state or in solution. The crystals of Cu8 are still suitable for single crystal X-ray diffraction analysis even after being treated with boiling water, 8 wt % H2 O2 , high concentrated acid (1 M HCl) or saturated base (≈20 M KOH), respectively. More importantly, the structure of Cu8 in solution also remained intact toward oxygen, organic acid (100 eq. HOAc) or base (400 eq. dibutylamine) confirmed by 1 H NMR and UV/Vis analysis. Taking advantage of high alkali-resistant, Cu8 illustrates excellent catalytic activity for the synthesis of indolizines, and it can be reused for at least 10 cycles without losing catalytic performance.

Application Value of Machine Learning Method in Measuring Gray Matter Volume of AIDS Patients.

Background: To investigate the role of gray matter (GM) volume in the identification of HIV-positive patients with HIV-associated neurocognitive impairment (HAND) using a machine learning approach from normal healthy controls. Methods: Twenty-seven HIV-infected patients and 14 healthy controls were enrolled in our study. Each set of BRAVO images was postprocessed using DPARSF3.1 to coregister all brains on the MNI template, and volume extraction of 90 brain regions was performed using custom-designed code. The machine learning method was performed using PRoNTo2.1.1 toolbox. The differences in brain volume between the HAND and non-HAND groups were analyzed. Results: GM volume effectively distinguished HIV-positive patients from healthy subjects with an AUC equals to 0.73. The sensitivity, specificity, and accuracy of the established classification were 85.19%, 42.86%, and 70.73%, respectively. GM volume value of the top ten brain regions was related to digit symbols, trail making test, digit span, vocabulary fluency, stroop C time, stroop CW time, CD4, and neuropsychological group. Conclusions: A machine learning approach facilitates early diagnosis of HAND in HIV patients by MRI-based GM volume measurement.

Characterization of NDM-5-producing Enterobacteriaceae isolates from retail grass carp ( Ctenopharyngodon idella) and evidence of bla NDM-5-bearing IncHI2 plasmid transfer between ducks and fish.

We aimed to characterize NDM-5-producing Enterobacteriaceae from aquatic products in Guangzhou, China. A total of 196 intestinal samples of grass carp collected in 2019 were screened for carbapenemase genes. Characterization of bla NDM-5 positive isolates and plasmids was determined by antimicrobial susceptibility testing, conjugation experiments, Illumina HiSeq, and Nanopore sequencing. One Citrobacter freundii and six Escherichia coli strains recovered from seven intestinal samples were verified as bla NDM-5 carriers (3.57%, 7/196). The bla NDM-5 genes were located on the IncX3 ( n=5), IncHI2 ( n=1), or IncHI2-IncF ( n=1) plasmids. All bla NDM-5-bearing plasmids were transferred by conjugation at frequencies of ~10 -4-10 -6. Based on sequence analysis, the IncHI2 plasmid pHNBYF33-1 was similar to other bla NDM-5-carrying IncHI2 plasmids deposited in GenBank from Guangdong ducks. In all IncHI2 plasmids, bla NDM-5 was embedded in a novel transposon, Tn 7051 (IS 3000-ΔIS Aba125-IS 5-ΔIS Aba125- bla NDM-5- ble MBL- trpF- tat-∆ dct-IS 26-∆ umuD-∆IS Kox3-IS 3000), which was identical to the genetic structure surrounding bla NDM-5 found in some IncX3 plasmids. The IncHI2-IncF hybrid plasmid pHNTH9F11-1 was formed by homologous recombination of the bla NDM-5-carrying IncHI2 plasmid and a heavy-metal-resistant IncF plasmid through ∆Tn 1721. To the best of our knowledge, this is the first report on the characterization of bla NDM-5-bearing plasmids in fish in China. The IncHI2 plasmid pHNBYF33-1 may be transmitted from ducks, considering the common duck-fish freshwater aquaculture system in Guangdong. Tn 7051 is likely responsible for the transfer of bla NDM-5 from IncX3 to IncHI2 plasmids in Enterobacteriaceae, resulting in the expansion of transmission vectors of bla NDM-5.

Factors Influencing Sodium Valproate Serum Concentrations in Patients with Epilepsy Based on Logistic Regression Analysis.

BACKGROUND We aimed to explore the risk factors that affect the serum concentration of sodium valproate (VPA-Na) in patients with epilepsy and to provide references for the rationale of the use of VPA-Na. MATERIAL AND METHODS The enzyme-multiplied immunoassay technique was used to determine the serum VPA-NA concentrations of 109 patients, and the results were retrospectively analyzed and summarized. A multivariate logistic regression model was used to analyze substandard serum VPA-Na concentrations. RESULTS Fifty-six patients (51.38%) treated with VPA-Na tablets were within the effective treatment range of 50-100 µg/mL, while 53 patients (48.62%) were out of the treatment range. The results indicated that the standard-reaching rate of serum drug concentration in the juvenile group was higher than that in the adult and elderly groups; the standard-reaching rates of serum drug concentrations in the low-dose group and the intermediate-dose group were lower than that in the high-dose group; and the standard-reaching rate of serum drug concentration in the group receiving carbapenems in combination was lower than that in the non-combination group; all differences were statistically significant. The combination with carbapenems and enzyme inducers was an independent risk factor for VPA-Na serum concentration below the target level in hospitalized patients. CONCLUSIONS To improve clinical efficacy and reduce the occurrence of adverse reactions, there is a need for therapeutic drug monitoring of VPA-Na. Moreover, individual administration should be implemented when VPA-Na tablets are used in the treatment of epilepsy because of the significant fluctuation in VPA-Na blood concentration.

Hydrolysis of methylphosphonic anhydride solid to methylphosphonic acid probed by Raman and infrared reflectance spectroscopies.

Much is still unknown about the mechanisms and rates of environmental degradation of organophosphorous pesticides and agents. In this study we focus on the degradation of one organophosphorous compound, namely solid methylphosphonic anhydride [CH3P(O)OHOP(O)OHCH3, MPAN] and its rate of conversion to methylphosphonic acid (MPA) via heterogeneous hydrolysis. Pure MPAN was synthesized and loaded in open sample cups placed inside exposure chambers containing saturated salt solutions to control the relative humidity (RH). The reaction was monitored in the sample cup at various times using both infrared hemispherical reflectance (HRF) spectroscopy and Raman spectroscopy. Calibrated HRF and Raman spectra of both pure reagents as well as gravimetrically prepared mixtures were used to quantify the concentrations of MPAN and MPA throughout the reaction. Results show both HRF and Raman spectroscopies are convenient non-invasive methods for detection of solid chemicals as long as a large area is sampled to average out any spatial inhomogeneities that occur on the sample surface and minimal phase changes occur during the course of the reaction. The samples for the 54 and 75% RH studies showed significant deliquescence, and the liquid water had to be removed prior to measurement; this effect led to differences in the sample form, such that the calibration spectra were no longer valid for quantitative analysis using HRF spectroscopy. Raman spectroscopy, on the other hand, proved to be less sensitive to these effects and provided better estimation of the MPAN and MPA concentrations. The MPAN degradation rate displayed a very strong dependence on relative humidity: at room temperature the reaction showed 50% conversion of the MPAN in 761 ± 54 h at 33% RH, 33 ± 4 h at 43% RH, 17 ± 2 h at 54% RH and just 7 ± 1 h at 75% RH.

Zinc Supplementation Forms Influenced Zinc Absorption and Accumulation in Piglets.

The study aimed at determining the effect of different zinc (Zn) supplementation forms on Zn accumulation, activities of Zn-containing enzymes, gene expression of metallothionein (MT), and Zn transporters in piglets. Eighteen piglets were randomly divided into three groups: (a) a basal diet supplemented with 150 mg/kg Zn from Zn methionine (Zn-Met) in the feed (Zn-Met group), (b) a basal diet supplemented with 150 mg/kg Zn from Zn sulfate (ZnSO4) in the feed (ZnSO4, feed group), and (c) a basal diet supplemented with the same dose of Zn as in ZnSO4,feed group but in water (ZnSO4, water group). The results showed that Zn-Met added in feed and ZnSO4 dissolved in drinking water significantly improved (p < 0.05) the Zn concentration in liver and jejunum and the apparent digestibility of Zn in comparison with the ZnSO4 added in feed. In addition, dietary Zn supplementation as Zn-Met significantly increased (p < 0.05) the activity of alkaline phosphatase (AKP) in the jejunum of piglets in comparison with the ZnSO4, feed group. Furthermore, the Zn-Met and ZnSO4, water groups showed an improved total superoxide dismutase activity (T-SOD) in the ileum as compared to the ZnSO4, feed group. Meanwhile, the qPCR and western blot results showed that Zn-Met and ZnSO4 dissolved in drinking water increased the expression of MT in the jejunum in comparison with the ZnSO4 added in the piglets' feed. However, different Zn supplementation forms had no effect on the mRNA expressions of Zip4 and ZnT1 transporters. In conclusion, Zn-Met added in feed and ZnSO4 dissolved in drinking water had higher bioavailability in piglets.

Corrigendum: Role of MicroRNA-143 in Nerve Injury-Induced Upregulation of Dnmt3a Expression in Primary Sensory Neurons.

[This corrects the article DOI: 10.3389/fnmol.2017.00350.].

Author Correction: DNA methyltransferase DNMT3a contributes to neuropathic pain by repressing Kcna2 in primary afferent neurons.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Ultrafast Semi-Solid Processing of Highly Durable ZIF-8 Membranes for Propylene/Propane Separation.

ZIF-8 membranes have emerged as the most promising candidate for propylene/propane (C3 H6 /C3 H8 ) separation through its precise molecular sieving characteristics. The poor reproducibility and durability, and high cost, thus far hinder the scalable synthesis and industrial application of ZIF-8 membranes. Herein, we report a semi-solid process featuring ultrafast and high-yield synthesis, and outstanding scalability for reproducible fabrication of ZIF-8 membranes. The membranes show excellent C3 H6 /C3 H8 separation performance in a wide temperature and pressure range, and remarkable stability over 6 months. The ZIF-8 membrane features dimethylacetamide entrapped ZIF-8 crystals retaining the same diffusion characteristics but offering enhanced adsorptive selectivity for C3 H6 /C3 H8 . The ZIF-8 membrane was prepared on a commercial flat-sheet ceramic substrate. A prototypical plate-and-frame membrane module with an effective membrane area of about 300 cm2 was used for efficient C3 H6 /C3 H8 separation.

N6-Methyladenosine Demethylase FTO Contributes to Neuropathic Pain by Stabilizing G9a Expression in Primary Sensory Neurons.

Nerve injury-induced change in gene expression in primary sensory neurons of dorsal root ganglion (DRG) is critical for neuropathic pain genesis. N6-methyladenosine (m6A) modification of RNA represents an additional layer of gene regulation. Here, it is reported that peripheral nerve injury increases the expression of the m6A demethylase fat-mass and obesity-associated proteins (FTO) in the injured DRG via the activation of Runx1, a transcription factor that binds to the Fto gene promoter. Mimicking this increase erases m6A in euchromatic histone lysine methyltransferase 2 (Ehmt2) mRNA (encoding the histone methyltransferase G9a) and elevates the level of G9a in DRG and leads to neuropathic pain symptoms. Conversely, blocking this increase reverses a loss of m6A sites in Ehmt2 mRNA and destabilizes the nerve injury-induced G9a upregulation in the injured DRG and alleviates nerve injury-associated pain hypersensitivities. FTO contributes to neuropathic pain likely through stabilizing nerve injury-induced upregulation of G9a, a neuropathic pain initiator, in primary sensory neurons.

A MOF Glass Membrane for Gas Separation.

Metal-organic framework (MOF) glasses are promising candidates for membrane fabrication due to their significant porosity, the ease of processing, and most notably, the potential to eliminate the grain boundary that is unavoidable for polycrystalline MOF membranes. Herein, we developed a ZIF-62 MOF glass membrane and exploited its intrinsic gas-separation properties. The MOF glass membrane was fabricated by melt-quenching treatment of an in situ solvothermally synthesized polycrystalline ZIF-62 MOF membrane on a porous ceramic alumina support. The molten ZIF-62 phase penetrated into the nanopores of the support and eliminated the formation of intercrystalline defects in the resultant glass membrane. The molecular sieving ability of the MOF membrane is remarkably enhanced via vitrification. The separation factors of the MOF glass membrane for H2 /CH4 , CO2 /N2 and CO2 /CH4 mixtures are 50.7, 34.5, and 36.6, respectively, far exceeding the Robeson upper bounds.

Effects of rosmarinic acid on immunoregulatory activity and hepatocellular carcinoma cell apoptosis in H22 tumor-bearing mice.

Rosmarinic acid (RA) is a natural polyphenolic compound that exists in many medicinal species of Boraginaceae and Lamiaceae. The previous studies have revealed that RA had therapeutic effects on hepatocellular carcinoma (HCC) in the H22-xenograft models by inhibiting the inflammatory cytokines and NF-κB p65 pathway in the tumor microenvironment. However, its molecular mechanisms of immunoregulation and pro-apoptotic effect in HCC have not been fully explored. In the present study, RA at 75, 150, and 300 mg/kg was given to H22 tumor-bearing mice via gavage once a day for 10 days. The results showed that RA can effectively inhibit the tumor growth through regulating the ratio of CD4+/CD8+ and the secretion of interleukin (IL)-2 and interferon-γ, inhibiting the expressions of IL-6, IL-10 and signal transducer and activator of transcription 3, thereby up-regulating Bax and Caspase-3 and down-regulating Bcl-2. The underlying mechanisms involved regulation of immune response and induction of HCC cell apoptosis. These results may provide a more comprehensive perspective to clarify the anti-tumor mechanism of RA in HCC.

Substituents lead to differences in the formation of two different butterfly-shaped NiDy clusters: structures and multistep assembly mechanisms.

The most effective way to understand reaction mechanisms and kinetics is to identify the reaction intermediates and determine the possible reaction patterns. The influencing factors that must be considered in the self-assembly of clusters are the type of ligand, metal ion, coordination anion and the pH of the solution. However, changes in ligand substituents resulting in different self-assembly processes to obtain different types of structures are still very rare, especially with -H and -CH3 substituents, which do not exert significant steric hindrance effects. In this study, planar mononuclear Ni(L1)2 (L1 = 2-ethoxy-6-(iminomethyl)phenol) was dissolved in methanol and combined with Dy(NO3)3·6H2O for 48 h at room temperature to obtain a butterfly-like Ni2Dy2 cluster ([Dy2Ni2(L1)4(CH3O)2(NO3)4], 1). The Dy(iii) ions in cluster 1 are in an O8N coordination environment, and the Ni(ii) ions are in an O5N coordination environment. High-resolution electrospray ionization mass spectrometry (HRESI-MS) was used to track species changes during the formation of cluster 1. Six key intermediate fragments were screened, and the self-assembly mechanism was proposed as Ni(L1)2→ HL1 + NiL1→ DyL1/Ni(L1)2'→ DyNi(L1)2→ Dy2Ni2(L1)4. Through this assembly mechanism, we found that Ni(L1)2 was first cleaved into HL1 + NiL1 and then further assembled to obtain 1. Another butterfly-like tetranuclear heterometallic cluster ([Dy2Ni2(L2)4(CH3O)2(NO3)4], 2) was obtained using planar mononuclear Ni(L2)2 (L2 = (E)-2-ethoxy-6-((methylimino)methyl)phenol) with -CH3 substitution on the nitrogen atom under the same reaction conditions. The structural analysis of cluster 2 showed that the Dy(iii) ions are in an O9 coordination environment, and the Ni(ii) ions are in an O4N2 coordination environment. HRESI-MS was used to trace species changes during the formation of 2, and the assembly mechanism was proposed as Ni(L2)2→ DyNi(L2)2→ Dy2Ni(L2)2→ Dy2Ni2(L2)4. Analysis of the assembly mechanism of 2 showed that Ni(L2)2 was twisted during the reaction, and its coordination point was exposed to capture the Dy(iii) ions. Finally, Dy(NO3)3·6H2O was replaced with NaN3 to obtain a [Ni2Na2(L2)4(N3)4] cluster (3) under the same reaction conditions and verify the above-mentioned torsion step. HRESI-MS was also used to trace the assembly process, and the assembly mechanism was proposed as Ni(L2)2→ NiNa(L2)2→ NiNa2(L2)2→ Ni2Na2(L2)4. Herein, the effect of interference from substitution and the regulation self-assembly process were discovered in the formation of 3d-4f heterometallic clusters, and different types of coordination clusters were obtained.

[Role of ZHX2 in regulating dorsal root ganglion µ-opioid receptor expression in mice with peripheral nerve injuryinduced pain hypersensitivity].

OBJECTIVE: To investigate the role of zinc-fingers and homeoboxes 2 (ZHX2) in regulating µ-opioid receptor expression in the dorsal root ganglion (DRG) in mice with peripheral nerve injury-induced pain hypersensitivity. METHODS: Forty-eight male adult C57BL6J mice were randomized into 4 groups and subjected to chronic constriction injury (CCI) of the sciatic nerve or sham operation followed by microinjection of a specific small interfering RNA (siRNA) of ZHX2 or a negative control siRNA sequence (siNC) into the DRG. Seven days later, the mice were examined for changes in the hind paw withdrawal frequency (PWF), after which the DRG tissue was collected for detecting the expressions of µ-opioid receptor at the mRNA and protein levels using RT-qPCR and Western blotting. In another experiment, the DRG tissues were collected from 6 mice (21-day-old) for primary culture of the DRG neurons, which were transfected with ZHX2 siRNA or the siNC to observe the changes in the expressions of ZHX2 and µ-pioid receptor. RESULTS: Microinjection of ZHX2 siRNA into the ipsilateral L3 and L4 DRGs significantly reversed CCI-induced µ-pioid receptor downregulation in the injured DRG and alleviated CCI-induced mechanical allodynia in the mice. In the cell experiment, ZHX2 knockdown obviously upregulated the mRNA and protein expressions of opioid receptor in the primary cultured DRG neurons. CONCLUSIONS: ZHX2 knockdown in the DRG reverses CCI-induced down-regulation of µ opioid receptor to alleviate periphery nerve injury-induced pain hypersensitivity in mice.

Tracking the Multistep Formation of Ln(III) Complexes with in situ Schiff Base Exchange Reaction and its Highly Selective Sensing of Dichloromethane.

Four complexes, namely, [Ln2(L2)2(NO3)4]. 2CH3OH (Ln = Tb (1), Dy (2), Ho (3), Er (4), and L2 = (E)-2-methoxy-6-(((pyridin-2-ylmethyl)imino)methyl)phenol), were obtained by reacting (E)-2-((3-methoxy-2-oxidobenzylidene)amino)ethanesulfonate (L1), Ln(NO3)3·6H2O, and 2-aminomethylpyridine at room temperature under solvothermal conditions in methanol for 12 h. The new Schiff base L2 was generated in situ based on the organic ligand L1 and 2-aminomethylpyridine through Schiff base exchange reaction by using lanthanide salts as inductor. A combination of crystallography and mass spectrometry was performed to track the exchange reaction, and the underlying mechanism accompanied by the complex assembly process was clearly presented. The multistep formation mechanism of the above dinuclear complex was also proposed, i.e., [L1] → Dy[L1]/[L2] → Dy[L2] → Dy[L2]2 → Dy2[L2]2. Luminescence test of 1 showed that it had extremely high selectivity to dichloromethane (CH2Cl2). Therefore, we established a quick, simple, and efficient method of detecting CH2Cl2 that enabled strong-luminescence observation with the naked eye. Tests for small amounts of CH2Cl2 in water further indicated the potential of 1 as a test strip for CH2Cl2 fluorescence detection in water samples. Alternating-current magnetic susceptibility studies indicated the field-induced single-molecule magnet behavior of 2.

Pathogenicity of an FAdV-4 isolate to chickens and its genomic analysis.

Fowl adenovirus serotype 4 (FAdV-4) strain SD1511 was isolated from chickens with severe inclusion body hepatitis and hydropericardium syndrome in Shandong Province, China. The isolate was cultured in primary chicken embryo kidney cells. A study of pathogenicity indicated that SD1511 readily infected 7-35-d-old chickens by intramuscular injection and intranasal and oral routes, causing 50%-100% mortality. The 35-d-old chickens suffered more severe infection than 7- and 21-d-old chickens with mortality highest in the intramuscular injection group. The serum from surviving chickens showed potent viral neutralizing capability. The complete genome of SD1511 was sequenced and analyzed. The strain was found to belong to the FAdV-4 cluster with more than 99% identity with the virulent FAdV-4 strains isolated in China in recent years except for some distinct variations, including deletions of open reading frame 27 (ORF27), ORF48, and part of ORF19. Our findings suggest that SD1511 might be used as a prototype strain for the study of pathogenesis and vaccine development.

Formation of nanocluster {Dy12} containing Dy-exclusive vertex-sharing [Dy4(µ3-OH)4] cubanes via simultaneous multitemplate guided and step-by-step assembly.

The formation of high-nuclearity clusters of lanthanide usually involves many complicated self-assembly processes. Thus, tracking the formation process is extremely difficult and research on the assembly mechanism is very rare. In this study, a Dy-exclusive nanocluster containing vertex-sharing [Dy4(µ3-OH)4] cubanes, denoted as [Dy12(L)8(OH)16(CH3O)8(H2O)8]·(CH3O)4 (Dy12, L = quinoline-2-carboxylate), was designed and synthesized from L and DyCl3·6H2O. Eight quinoline-2-carboxylate ligands were encapsulated on the periphery of the Dy12 cluster, which served to stabilize the core. The high stability of the Dy12 cluster core was further confirmed by high-resolution electrospray-ionization mass spectrometry (HRESI-MS). With increased ion-source energy, only CH3O- and OH- bridging ligands were replaced inside the Dy12 cluster. Notably, eight intermediate fragments were successfully observed from the Dy12 cluster formation by time-dependent HRESI-MS. First, ligand L captured Dy3+ to give Dy1, which further formed Dy2 through µ2-O bridging. The Dy12 cluster was constructed in one step with four Dy2 and four Dy3+ as templates: L → Dy1→ Dy2→ Dy12. Moreover, a series of Dy3-Dy6 fragment peaks with relatively weak intensities were observed, and an alternative stepwise-assembly route was proposed: L → Dy1→ Dy2→ Dy3→ Dy4→ Dy5→ Dy6→ Dy12. On comparing the two different assembly methods, the multitemplate guided assembly formed Dy12 was found to be dominant. To the best of our knowledge, this study was the first to propose the involvement of two self-assembly mechanisms in the construction of lanthanide clusters, as further confirmed by HRESI-MS. Magnetic studies further showed that Dy12 clusters exhibited field-induced single-molecule magnet behavior.