Coordinated Solvent Molecules Research Articles

A Mixed Heterobimetallic Y/Eu-MOF for the Cyanosilylation and Hydroboration of Carbonyls

Herein, to the best of our knowledge, the first heterobimetallic Y/Eu porous metal–organic framework (MOF), based on 3-amino-4-hydroxybenzoic acid (H2L) ligand, with the following formulae {[Y3.5Eu1.5L6(OH)3(H2O)3]·12DMF}n (in advance, namely Y/Eu-MOF), is described. The three-dimensional structure has been synthesized by solvothermal routes and thoroughly characterized, by means of single crystal X-ray diffraction, powder X-ray diffraction, electronic microscopy, ICP-AES, electrophoretic mobility, and FTIR spectra. Intriguingly, the porous nature allows for coordinated solvent molecules displacement, yielding unsaturated metal centers, which can act as a Lewis acid catalyst. This novel supramolecular entity has been tested in cyanosilylation and hydroboration reactions on carbonyl substrates of a diverse nature, exhibiting an extraordinary activity.

Constructing [Co6(μ3-OH)6]-based pillar-layered MOF with open metal sites via steric-hindrance effect on ligand for CO2 adsorption and fixation

With excellent structural tunability and well framework stability, pillar-layered metal-organic frameworks (PL-MOFs) are promising candidates as sorbents and catalysts. Yet, the open metal sites (OMSs) in PL-MOFs are usually fully occupied by the pillar ligands, mostly limiting their involvement in CO2 adsorption and fixation. Herein, in consideration of the 12-connected [Co6(μ3-OH)6]-based PL-MOFs (Co6-MOF-3), a strategy based on steric-hindrance effect on pillar linker is proposed to create OMSs on their metal cluster nodes. The 4,4′-(9,10-anthracenediyl)bis-Pyridine (ABPY) that possessed anthracene groups was selected as the pillar linker, and a new [Co6(μ3-OH)6]-based PL-MOF (DZU-6) with accessible open Co(ii) sites was successfully synthesized. Single crystal structure of DZU-6 analysis reveals that ABPY ligands which were firstly linked to the metal clusters prevented the other ABPY ligands from coordinating with the nodes due to the steric-hindrance effect on ligands, resulting that four sites on [Co6(μ3-OH)6] were occupied by the terminal solvent molecules. The coordinated solvent molecules in DZU-6 could be removed easily, meanwhile the porosity was preserved (BET surface 2566 m2 g−1). Importantly, CO2 adsorption and catalytic cycloaddition conversion of DZU-6 were performed that the CO2 uptake improved 40% and the catalytic conversion yield increased over 50% compared with isostructural Co6-MOF-3 without OMSs.

Solvothermal synthesis of a new heterometallic Cd–Ba compound based on terephthalic acid: Catalytic property and therapeutic effect on diabetes

Presented is a new heterometallic compound, namely [Cd2Ba2(pdc)4(H2O)4(DMA)2]}n·n(H2O) (1, H2pdc = terephthalic acid, DMA is N, N′-dimethylacetamide), which was created with the solvothermal reaction. The architectural analysis of X-ray indicated that the 1 reveals a three-dimensional skeleton according to one-dimensional infinite chains. After removal of the free along with coordinated solvent molecules, it contains 49.8% solvent-accessible volume and unsaturated coordination sites. The solvent-free form of 1 exhibits excellent catalytic effect for the addition reaction between diethylzinc and benzaldehyde. Its therapeutic effect and mechanism exploration on diabetes was conducted in this present research. Firstly, the abundance of intestinal flora in the gut was detected with real time RT-PCR assay. Besides, the measurement of the levels of sugar was conducted with blood glucose meter in the T2DM animal after compound treatment. The cytotoxicity of the 1 was evaluated with CCK-8 assay.

Enhancing magnetic relaxation through subcomponent self-assembly from a Dy2 to Dy4 grid.

The subcomponent self-assembly of 4,6-dihydrazinopyrimidine and o-vanillin/salicylaldehyde with different DyIII salts leads to the formation of Dy2 (1-3) and grid-like Dy4 (4) compounds with formulas of [Dy2L(DMF)4(NO3)4]·2DMF (1), [Dy2L2(CH3COO)4(CH3OH)2]·10H2O (2), [Dy2L'2(CH3COO)4(CH3OH)2]·2H2O·2CH3OH (3) and [Dy4Na2L2(μ2-OH)2(PhCOO)8(CH3OH)(H2O)]·CH3CN·2CH3OH·7H2O (4). In all cases, the DyIII ions are nine coordinate but the different features of coordinated solvent molecules and anions result in diverse coordination geometries in their respective structures. Notably, by introducing various axial coordinating anions with different electronegativities (NO3-, CH3COO- and C6H5COO-), the effective energy barriers were progressively enhanced (52-207 K) in this system. Detailed magnetic studies for these complexes revealed obvious magnetic interactions in complex 1 and clear single molecule magnet (SMM) behavior with anisotropy barriers of 52, 56 and 58.4 K for 1-3, respectively. Moreover, we find that the incorporation of benzoates into the axial position of the DyIII ions in complex 4 leads to the occurrence of two clear distinct relaxation processes, with energy barriers of 94.9 and 207.2 K, respectively. This result presents an example of the effects of axial coordinating anions on the SMM behavior, providing a valid route towards enhancing the slow magnetic relaxation of 4f based SMMs via incorporating diverse coordination anions into the subcomponent self-assembly system.

Self-assembling of three rare structurally various homomultinuclear CuII complexes derived from a bis(salamo)-based multioxime ligand

A family of rare structurally different homometal multinuclear CuII bis(salamo)-based complexes, [Cu4(L)2(MeOH)2](ClO4)2·2MeOH (1), [Cu4(L)2(EtOH)2](NO3)2·2EtOH (2) and [Cu2(HL)(EtOH)Br2]·CHCl3 (3), has been successfully synthesized by the reactions of cupric salts with a bis(salamo)-based multidentate chelate ligand (H3 L). The salamo-based ligand [R-CH=N—O—(CH2) n —O—N=CH—R] is a new type of salen-based analog. Complexes (1) and (2) are isostructural structures, and crystallize in monoclinic space group P21/n with centrosymmetric spiral structures, where the main structures contain two fully deprotonated ligand (L)3− units, a charged tetranuclear CuII folding center and two coordinated solvent molecules. Complex (3) crystallizes in monoclinic space group Cc and consists of two CuII cations, one incompletely deprotonated ligand (HL)2− unit and one coordinated ethanol molecule, and forms a novel homo-binuclear CuII complex structure due to Br− counter anions. Complexes (1)–(3) have zero-dimensional cluster-based structures and are further assembled into three-dimensional frameworks via intermolecular interactions. Because of the different solvents and counter anions which have a significant influence on the structures of complexes (1)–(3), the interactions were quantitatively evaluated by Hirshfeld surfaces analyses. Complexes (1)–(3) have been characterized by elemental analyses, IR spectra, UV–vis spectra and X-ray crystallography analyses. In addition, fluorescence properties are evaluated and DFT calculations are performed.

Sifting weakly-coordinated solvents within solvation sheath through an electrolyte filter for high-voltage lithium-metal batteries

The compulsive lithium dendrite growth and inevitable electrolyte decomposition induced by immediate contact between electrodes and free/weakly coordinated solvent molecules within the solvation sheaths of solvated lithium-ions are long-lasting tricky problems that existed in lithium-metal batteries (LMBs). Salt-concentrated strategy can effectively suppress those detrimental issues, the apparently increased production costs, the increased electrolyte viscosities, or even catastrophic battery explosions caused by adding extra salts, however, greatly restrained their successes. Here, by employing a metal-organic framework (MOF) with narrow channel sizes of 4.2 Å (ZIF-71) as a unique electrolyte solvation sheath filter to isolate free or weakly-coordinated solvents from contact with electrodes, we have obtained a special electrolyte composed of merely strongly coordinated solvent molecules. Drawn from the quantitative spectral analysis (FT-IR, Raman), the number of electrolyte solvent molecules in each Li+ solvation sheath was calculated to be 0.54 (the lowest value achieved among carbonate electrolytes), indicated almost completely de-solvation towards the solvated lithium-ions. This ZIF-71 filtered electrolyte displayed remarkably expanded electrochemical stability windows (extended to 5.2 V vs. Li/Li+). When coupled it with two typical high-voltage cathodes (4.4 V-level NCM-811 and 4.9 V-level LNMO), the high-voltage lithium-metal batteries demonstrated remarkably improved electrochemical performances in terms of capacities and lifespans. The cycled high-voltage cathodes and lithium metals demonstrate greatly improved electrode/electrolyte interfaces with negligible cathode electrolyte interface (CEI) and solid electrolyte interface (SEI). This special electrolyte filtering strategy is expected to push the development of high-energy-density LMBs.

Characterization of Americium and Curium Complexes with the Protein Lanmodulin: A Potential Macromolecular Mechanism for Actinide Mobility in the Environment.

Anthropogenic radionuclides, including long-lived heavy actinides such as americium and curium, represent the primary long-term challenge for management of nuclear waste. The potential release of these wastes into the environment necessitates understanding their interactions with biogeochemical compounds present in nature. Here, we characterize the interactions between the heavy actinides, Am3+ and Cm3+, and the natural lanthanide-binding protein, lanmodulin (LanM). LanM is produced abundantly by methylotrophic bacteria, including Methylorubrum extorquens, that are widespread in the environment. We determine the first stability constant for an Am3+-protein complex (Am3LanM) and confirm the results with Cm3LanM, indicating a ∼5-fold higher affinity than that for lanthanides with most similar ionic radius, Nd3+ and Sm3+, and making LanM the strongest known heavy actinide-binding protein. The protein's high selectivity over 243Am's daughter nuclide 239Np enables lab-scale actinide-actinide separations as well as provides insight into potential protein-driven mobilization for these actinides in the environment. The luminescence properties of the Cm3+-LanM complex, and NMR studies of Gd3+-LanM, reveal that lanmodulin-bound f-elements possess two coordinated solvent molecules across a range of metal ionic radii. Finally, we show under a wide range of environmentally relevant conditions that lanmodulin effectively outcompetes desferrioxamine B, a hydroxamate siderophore previously proposed to be important in trivalent actinide mobility. These results suggest that natural lanthanide-binding proteins such as lanmodulin may play important roles in speciation and mobility of actinides in the environment; it also suggests that protein-based biotechnologies may provide a new frontier in actinide remediation, detection, and separations.

Assessment of the thermal stability, catalytic behavior, and laser ignitability of energetic coordination polymer [Cu(HBTT)(H2O)

Solvent molecules, especially coordinated solvent molecules, vastly affect the energetic properties of energetic coordination polymers (ECPs). Therefore, an effective strategy to maintain energetic properties is to reduce solvent molecules. In this paper, a nitrogen-rich energetic coordination polymer [Cu(HBTT)(H2O)]n (ECP 1) was synthesized and prepared by integrating the coordination mode. Its properties were adequately investigated, including crystal structure, thermal stability, energetic properties, and sensitivity. In terms of application, it was researched as catalysts for the thermal decomposition of AP and as a primary explosive for laser initiation. As revealed by single-crystal X-ray diffraction results, it crystallizes in and belongs to monoclinic space group P21/n with a 2D layer-like structure. Meanwhile, it has outstanding thermal stability (Tp = 357.2 °C, Ek = 201.78 kJ mol-1) according to differential scanning calorimetry (DSC) curves and thermogravimetric curves (TG). The detonation velocity and detonation pressure of ECP 1 (8.63 km s-1, 36.73 GPa) can bear comparison with RDX and HMX. The catalytic pyrolysis experiment indicates that AP/ECP 1 (10 wt%) can accelerate the thermal decomposition of AP, with the high temperature for decomposition decreasing to nearly 80 °C. The activation energy (Ek) of AP decreased from 217.36 kJ mol-1 to 185.96 kJ mol-1 by adding ECP 1. Meanwhile, ECP 1 has a preliminary response to laser initiation. These results are conducive to the quick development of ECPs.

Redox property switching in MOFs with open metal sites for improved catalytic hydrogenation performance

In this study, a decompression-thermalization strategy was utilized for a Cu-containing metal-organic framework (MOF) to tune its redox and catalytic hydrogenation properties. Remarkably, at just 120 °C, open metal sites (OMSs) were successfully constructed by removing coordinated solvent molecules to generate the daughter MOF-120. The tailored redox property of MOF-120 is correlated with the presence of OMSs. Compared with the pristine MOF where copper cations were capped by DMF, MOF-120 exhibited improved kinetics, showed a reduction of activation energy and outstanding recyclability in the hydrogenation of 4-nitrophenol under mild conditions (25 °C, 1 atm). Both experimental studies and theoretical calculation results reveal that the generation of OMSs endows the Cu species with unique electronic properties, which assist the adsorption and electron transfer between substrate molecules and is responsible for the enhanced performance in the hydrogenation process.

Axial Heme Coordination by the Tyr-His Motif in the Extracellular Hemophore HasAp Is Critical for the Release of Heme to the HasR Receptor of Pseudomonas aeruginosa.

Pseudomonas aeruginosa senses extracellular heme via an extra cytoplasmic function σ factor that is activated upon interaction of the hemophore holo-HasAp with the HasR receptor. Herein, we show Y75H holo-HasAp interacts with HasR but is unable to release heme for signaling and uptake. To understand this inhibition, we undertook a spectroscopic characterization of Y75H holo-HasAp by resonance Raman (RR), electron paramagnetic resonance (EPR), and X-ray crystallography. The RR spectra are consistent with a mixed six-coordinate high-spin (6cHS), six-coordinate low-spin (6cLS) heme configuration and an H218O exchangeable FeIII-O stretching frequency with 16O/18O and H/D isotope shifts that support a two-body Fe-OH2 oscillator with (iron-hydroxy)-like character as both hydrogen atoms are engaged in short hydrogen bond interactions with protein side chains. Further support comes from the EPR spectrum of Y75H holo-HasAp that shows a LS rhombic signal with ligand-field splitting values intermediate between those of His-hydroxy and bis-His ferric hemes. The crystal structure of Y75H holo-HasAp confirmed the coordinated solvent molecule hydrogen bonded through H75 and H83. The long-range conformational rearrangement of HasAp upon heme binding can still take place in Y75H holo-HasAp, because the intercalation of a hydroxy ligand between the heme iron and H75 allows the variant to reproduce the heme binding pocket observed in wild-type holo-HasAp. However, in the absence of a covalent linkage to the Y75 loop combined with the malleability provided by the bracketing H75 and H83 hydrogen bonds, either the hydroxy sixth ligand remains bound after complexation of Y75H holo-HasAp with HasR or rearrangement and coordination of H85 prevent heme transfer.

Continuous Breathing Rare-Earth MOFs Based on Hexanuclear Clusters with Gas Trapping Properties

Guest responsive porous materials represent an important and fascinating class of multifunctional solids that have attracted considerable attention in recent years. An understanding of how these structures form is essential toward their rational design, which is a prerequisite for the development of tailor-made materials for advanced applications. We herein report a novel series of stable rare-earth (RE) MOFs that show a rare continuous breathing behavior and an unprecedented gas-trapping property. We used an asymmetric 4-c tetratopic carboxylate-based organic ligand that is capable of affording highly crystalline materials upon controlled reaction with RE cations. These MOFs, denoted as RE-thc-MOF-1 (RE: Y3+, Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, and Er3+), feature hexanuclear RE6 clusters that display a highly unusual connectivity and serve as unique 8-c hemi-cuboctahedral secondary building block, resulting in a new (3,3,8)-c thc topology. Extensive single-crystal to single-crystal structural analyses coupled with detailed gas (N2, Ar, Kr, CO2, CH4, and Xe) and vapor (EtOH, CH3CN, C6H6, and C6H14) sorption studies, supported by accurate theoretical calculations, shed light onto the unique swelling behavior. The results reveal a synergistic action involving steric effects, associated with coordinated solvent molecules and 2-fluorobenzoate (2-FBA) nonbridging ligands, as well as cation-framework electrostatic interactions. We were able to probe the individual role of the coordinated solvent molecules and 2-FBA ligands and found that both cooperatively control the gas-breathing and -trapping properties, while 2-FBA controls the vapor adsorption selectivity. These findings provide unique opportunities toward the design and development of tunable RE-based flexible MOFs with tailor-made properties.

Quenching Mechanism of Uranyl(VI) by Chloride and Bromide in Aqueous and Non-Aqueous Solutions

A major hindrance in utilizing uranyl(VI) luminescence as a standard analytical tool, for example, in environmental monitoring or nuclear industries, is quenching by other ions such as halide ions, which are present in many relevant matrices of uranyl(VI) speciation. Here, we demonstrate through a combination of time-resolved laser-induced fluorescence spectroscopy, transient absorption spectroscopy, and quantum chemistry that coordinating solvent molecules play a crucial role in U(VI) halide luminescence quenching. We show that our previously suggested quenching mechanism based on an internal redox reaction of the 1:2-uranyl-halide-complex holds also true for bromide-induced quenching of uranyl(VI). By adopting specific organic solvents, we were able to suppress the separation of the oxidized halide ligand X2·- and the formed uranyl(V) into fully solvated ions, thereby "reigniting" U(VI) luminescence. Time-dependent density functional theory calculations show that quenching occurs through the outer-sphere complex of U(VI) and halide in water, while the ligand-to-metal charge transfer is strongly reduced in acetonitrile.

Self-Assembled Nickel-4 Supramolecular Squares and Assays for HER Electrocatalysts Derived Therefrom.

Solid-state structures find a self-assembled tetrameric nickel cage with carboxylate linkages, [Ni(N2S'O)I(CH3CN)]4 ([Ni-I]40), resulting from sulfur acetylation by sodium iodoacetate of an [NiN2S]22+ dimer in acetonitrile. Various synthetic routes to the tetramer, best described from XRD as a molecular square, were discovered to generate the hexacoordinate nickel units ligated by N2Sthioether, iodide, and two carboxylate oxygens, one of which is the bridge from the adjacent nickel unit in [Ni-I]40. Removal of the four iodides by silver ion precipitation yields an analogous species but with an additional vacant coordination site, [Ni-Solv]+, a cation but with coordinated solvent molecules. This also recrystallizes as the tetramer [Ni-Solv]44+. In solution, dissociation into the (presumed) monomer occurs, with coordinating solvents occupying the vacant site [Ni(N2S'O)I(solv)]0, ([Ni-I]0). Hydrodynamic radii determined from 1H DOSY NMR data suggest that monomeric units are present as well in CD2Cl2. Evans method magnetism values are consistent with triplet spin states in polar solvents; however, in CD2Cl2 solutions no paramagnetism is evident. The abilities of [Ni-I]40 and [Ni-Solv]44+ to serve as sources of electrocatalysts, or precatalysts, for the hydrogen evolution reaction (HER) were explored. Cyclic voltammetry responses and bulk coulometry with gas chromatographic analysis demonstrated that a stronger acid, trifluoroacetic acid, as a proton source resulted in H2 production from both electroprecatalysts; however, electrocatalysis developed primarily from uncharacterized deposits on the electrode. With acetic acid as a proton source, the major contribution to the HER is from homogeneous electrocatalysis. Overpotentials of 490 mV were obtained for both the solution-phase [Ni-I]0 and [Ni-Solv]+. While the electrocatalyst derived from [Ni-Solv]+ has a substantially higher TOF (102 s-1) than [Ni-I]0 (19 s-1), it has a shorter catalytically active lifespan (4 h) in comparison to [Ni-I]0 (>18 h).

The synthesis, structure, and magnetic properties of nickel (II) 6-coordinate species with several substituted aniline ligands

A family of Ni(II) halide complexes of substituted aniline derivatives were prepared and studied via single-crystal X-ray diffraction and variable temperature magnetic measurements: [Ni(4-Mean)4Cl2] 1, [Ni(4-Clan)2Cl2(MeOH)2] 2, [Ni(4-Clan)2Br2(EtOH)2] 3, [Ni(4-Clan)4Br2] (4-Clan) 4, [Ni(4-Clan)2Br2(H2O)2] 5, [Ni(4-MeOan)2Br2(H2O)2] 6, [Ni(3-MeOan)4Cl2] 7, [Ni(3-MeOan)4Br2] 8, [Ni(4-MeOan)4Cl2] 9, [Ni(4-MeOan)4(H2O)2](Br)210, and [(4-MeOan)2(DMSO)4Ni](Br)211 (4-Mean = 4-methylaniline, 4-Clan = 4-chloroaniline, 3-MeOan = 3-methoxyaniline, 4-MeOan = 4-methoxyaniline). All complexes are six-coordinate, filling the coordination sphere with a combination of halide ions, aniline-based ligands and/or solvent molecules. The complexes demonstrate variable stability once removed from the mother liquor with loss of coordinated solvent molecules being common. Analysis of the magnetic properties of the compounds shows the presence of single-ion anisotropy, weak interactions, or a combination thereof.

Phototriggered cytotoxic properties of tricarbonyl manganese(I) complexes bearing α-diimine ligands towards HepG2.

Reaction between bromo tricarbonyl manganese(I) and N,N'-bis(phenyl)-1,4-diaza-1,3-butadiene ligands, bearing different electron-donating and electron-withdrawing groups R=OCH3, Cl, and NO2 in the ortho- and para-positions on the phenyl substituent, afforded [MnBr(CO)3(N-N)] complexes. The influence of the character and position of the substituent on the dark stability and carbon monoxide releasing kinetics was systematically investigated and correlated with the data of the time-dependent density functional theory calculations. The combined UV/Vis and IR data clearly revealed that the aerated solutions of [MnBr(CO)3(N-N)] in either coordinating or noncoordinating solvents are dark stable and the fluctuations observed during the incubation period especially in the case of the nitro derivatives may be attributed to the exchange of the axial bromo ligand with the coordinating solvent molecules. The free ligands and nitro complexes were non-cytotoxic to HepG2 cells under both the dark and illumination conditions. In the dark, Mn(I) compounds, incorporating o-OCH3 and o-Cl, exhibited excellent cytotoxicity with IC50 values of 18.1 and 11.8μM, while their para-substituted analogues were inactive in the dark and active upon the irradiation at 365nm with IC50 values of 5.7 and 6.7μM, respectively.

Solvent-Dependent Assembly and Magnetic Relaxation Behaviors of [Cu4I3] Cluster-Based Lanthanide MOFs: Acting as Efficient Catalysts for Carbon Dioxide Conversion with Propargylic Alcohols.

Two structurally similar metal-organic frameworks (MOFs) [Dy2Cu4I3(IN)7(DMF)2]·DMF (1) and [Dy2Cu4I3(IN)7(DMA)2]·DMA (2) (HIN = isonicotinic acid) feathering different coordinated solvent molecules were successfully isolated by tuning the types of solvents in the reaction system. Structural tests indicate that 1 and 2 are both built from 1D Dy(III) chains and copper iodide clusters [Cu4I3], generating into three-dimensional frameworks with an open 1D channel along the a axis. 1 and 2 display extensive and excellent solvent stability. Magnetic studies of 1 and 2 indicate that they exhibit interesting solvent-dependent magnetization dynamics. Importantly, 1 and 2 can act as highly effective catalysts for the carboxylic cyclization of propargyl alcohols with carbon dioxide (CO2) under ambient operating conditions. Additionally, the substrate scope was further explored over compound 1 based on the optimal conditions, and it exhibits efficient cyclic carboxylation of various terminal propargylic alcohols with CO2. This research offers an effective approach for the solvent-guided synthesis of MOFs materials and also presents the great application value of MOFs in CO2 chemical conversion.

Synthesis, structural characterization, and properties of triorganotin complexes of Schiff base derived from 3‐aminobenzoic acid and salicylaldehyde or 2,4‐pentanedione

Six new triorganotin 3‐(salicylideneamino)benzoates (1a–1c) and 3‐(4‐oxo‐2‐penten‐2‐ylamino)benzoates (2a–2c), 3‐(2‐HOC6H4CH=N)C6H4COOSnR3, and 3‐(CH3COCH=C(CH3)NH)C6H4COOSnR3 (R = Ph, a; Cy, b; Bu, c) have been synthesized by one‐pot reaction of 3‐aminobenzoic acid, salicylaldehyde (or 2,4‐pentanedione), and triorganotin hydroxide and characterized by elemental analysis, infrared, and nuclear magnetic resonance (1H, 13C, and 119Sn) spectra. The crystal structures of 1a, 1b, and 2a–2c have been determined by the single crystal X‐ray diffraction. Complexes 1a and 2a exhibit a 44‐membered macrocyclic tetramer and a polymeric zigzag chain, respectively, in which tin atoms show trans‐[C3SnO2] trigonal bipyramidal geometry with the axial positions being occupied by the carboxylate oxygen atom and the phenolic (or ketone) oxygen atom from another ligand. Complex 1b adopts a distorted tetrahedral geometry at tin, and there are two molecules differing in the relative orientation of the carboxylate toward the imino group. Compounds 2a⋅CH3OH, 2b⋅H2O, and 2c⋅H2O are five‐coordinated mononuclear adducts with one coordinated solvent molecule and display different supramolecular organizations in which there are the centrosymmetric R22(16), R42(22), and R64(34) macrocycle motifs formed by the O–H⋅⋅⋅O, N–H⋅⋅⋅O, and C–H⋅⋅⋅O hydrogen bonds. The fluorescence spectrum indicates that the complexes may be explored for potential blue luminescent materials. Compared to cisplatin, these compounds exhibit enhanced cytotoxic efficacy and can be considered as anticancer agents for further study.

Interactions between Ultrastable Na4Ag44(SR)30 Nanoclusters and Coordinating Solvents: Uncovering the Atomic-Scale Mechanism.

Recently, silver nanoclusters have garnered considerable attention after the high-yield synthesis and crystallization of a thiolate-protected silver nanocluster, Na4Ag44(SR)30 (SR, protecting thiolate ligand). One intriguing feature of Na4Ag44(SR)30 is its outstanding stability and resistance to chemical reactions, in striking difference from other silver nanostructures whose susceptibility to oxidation (tarnishing) has been commonly observed and thus limits their applications in nanotechnology. Herein, we report the mechanism on the ultrahigh stability of Na4Ag44(SR)30 by uncovering how coordinating solvents interact with the Na4Ag44(SR)30 nanocluster at the atomic scale. Through synchrotron X-ray experiments and theoretical calculations, it was found that strongly coordinating aprotic solvents interact with surface Ag atoms, particularly between ligand bundles, which compresses the Ag core and relaxes surface metal-ligand interactions. Furthermore, water was used as a cosolvent to demonstrate that semiaqueous conditions play an important role in protecting exposed surface regions and can further influence the local structure of the silver nanocluster itself. Notably, under semiaqueous conditions, aprotic coordinating solvent molecules preferentially remain on the metal surface while water molecules interact with ligands, and ligand bundling persisted across the varied solvation conditions. This work offers an atomic level mechanism on the ultrahigh stability of the Na4Ag44(SR)30 nanoclusters from the nanocluster-coordinating solvent interaction perspective, and implies that nanocluster-solvent interactions should be carefully considered moving forward for silver nanoclusters, as they can influence the electronic/chemical properties of the nanocluster as well as the surface accessibility of small molecules for potential catalytic and biomedical applications.

Creating uniform pores for xenon/ krypton and acetylene/ethylene separation on a strontium-based metal-organic framework

Industrial separations of xenon/krypton and acetylene/ethylene systems are challenging and energy-intensive processes. Exploring new porous material for their separation is of great significance. We reported here a strontium based thermostable metal-organic framework [Sr4(TCPE4−)2(DMF)4(H2O)4]n·solvent (1) (TCPE ​= ​tetrakis(4-carboxyphenyl)ethylene) with quadrangular pores possess diameter of 3.60 ​Å (type-1 pore). Heating the MOF 1 in vacuum can drive the coordinated solvent molecules away and open the type-2 pores with diameter of 4.40 ​Å. This contributes to xenon and acetylene absorption with Xe/Kr selectivity of 6.93 (Xe/Kr ​= ​20:80) and acetylene/ethylene selectivity of 1.75 (acetylene/ethylene ​= ​1:99). The density functional theory (DFT) calculations revealed the interactions between the MOF skeleton and the absorbed Xe atom.

Deciphering the Solvent Effect for the Solvation Structure of Ca2+ in Polar Molecular Liquids

Although the crystal structures for many inorganic compounds are readily available, researchers are still working hard to understand the relations between the structures and chemical properties of solutions because most of the chemical reactions take place in solutions. A huge amount of effort has been put toward modeling the ion solvation structure from the perspectives of both experiments and theories. In this study, the solvation structures of Ca2+ ions in aqueous and alcoholic solutions at different concentrations were carefully evaluated by Ca K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analyses. Density functional theory (DFT) calculations were also performed to correlate the results with the experimental data and then further extended to other similar systems. It was found that the number of coordinating solvent molecules decreases with increasing Ca2+ concentration and increasing solvent molecule sizes. From the EXAFS data, it was observed that the first solvation shell of Ca2+ splits into two Ca-O distances in a methanol solution and the counter ion Cl- might also be within the first shell at high concentrations. For the first time, the effects of solvents with different polarities and sizes on the ion solvation environment were systematically evaluated.