Supramolecular Interactions Induce Dynamics in Metal-Organic Layers to Selectively Separate Acetylene from Carbon Dioxide.

We report the synthesis and structural characterization of a 2D metal-organic framework with AB-packing layers, [Co2(pybz)2(CH3COO)2]·DMF (Co2, pybz= 4-(4-pyridyl)benzoate), containing a stable (4,4)-grid network fabricated by paddle-wheel nodes, ditopic pybz, and acetate ligands. After removal of the guest, the layer structure is retained but reorganized into an ABCD packing mode in the activated phase (Co2a). Consequently, the intralayer square windows (7.2 × 5.0 Å2) close, while the interlayer separation is decreased slightly from 3.69 to 3.45 Å, leaving a narrow gap. Importantly, the dangling methyl group of the acetate with H-bonds to the adjacent layers and also the well-distributed π-π interactions between the aromatic rings of neighboring layers facilitate the structural stability. These weak supramolecular interactions further allow for favorable dynamic exfoliation of the layers, which promotes efficient adsorption of C2H2 (41.6 cm3 g-1) over CO2 with an adsorption ratio of 6.3 (0.5 bar, 298 K). The effective separation performance of equimolar C2H2/CO2 was verified by cycling breakthrough experiments and was even tolerable to moisture (R.H = 52%). DFT calculations, in situ PXRD, and PDF characterization reveal that the favorable retention of C2H2 rather than that of CO2 is due to its H-bond formation with the paddle-wheel oxygen atoms that triggers the increase in interlayer separation during C2H2 adsorption.

An Ultrastable 155-Nuclei Silver Nanocluster Protected by Thiacalix[4]arene and Cyclohexanethiol for Photothermal Conversion.

Thiacalix[4]arenes have emerged as a family of macrocyclic ligands to protect metal nanoparticles, but it remains a great challenge to solve the mystery of their structures at the atomic level, especially for those larger than 2 nm. Here, we report the largest known mixed-valence silver nanocluster [Ag155 (CyS)40 (TC4A)5 Cl2 ] (Ag155) protected by deprotonated cyclohexanethiol (CySH) and macrocyclic ligand p-tert-butylthiacalix[4]arene (H4 TC4A). Its single-crystal structure consists of a metallic core of four concentric shells, Ag13 @Ag42 @Ag30 @Ag70 , lined with a organic skin of 40CyS- and 5TC4A4- and 2Cl- . Ag155 manifests an unusual pseudo-5-fold symmetry dictated by the intrinsic metal atom packing and the regioselective distribution of mixed protective ligands. This work not only reveals a macrocyclic ligand effect on the formation of a large silver nanocluster, but also provides a new structural archetype for comprehensively perceiving their interface and metal kernel structures.

A Domino Fusion of an Organic Ligand Depended on Metal-Induced and Oxygen Insertion, Unraveled by Crystallography, Mass Spectrometry, and DFT Calculations.

Herein, the reaction of (1-methyl-1 H-benzo[d]imidazol-2-yl)methanamine (L1) with Co(H2 O)6 Cl2 , in CH3 CN at 120 °C, leading to the 2,3,5,6-tetrakis(1-methyl-1 H-benzo[d]imidazol-2-yl)pyrazine (3), isolated as a dimeric cluster {[CoII 2 (3)Cl4 ]⋅2 CH3 CN} (2), is reported. When O2 and H2 O are present, (1-methyl-1 H-benzo[d]imidazole-2-carbonyl)amide (HL1') is first formed and crystallized as [CoIII (L1)2 (L1')]Cl2 ⋅2 H2 O (4) before fusion of HL1' with L1, giving 1-methyl-N-(1-methyl-1 H-benzo[d]imidazol-2-carbonyl)-1 H-benzo[d]imidazol-2-carboxamide (HL2'') forming a one-dimensional (1D) chain of [CoII 3 (L2'')2 Cl4 ]n (5). The combination of crystallography and mass spectrometry (ESI-MS) of isolated crystals and the solutions taken from the reaction as a function time reveal seven intermediate steps leading to 2, but six steps for 5, for which a different sequence takes place. Control and isotope labeling experiments confirm the two carbonyl oxygen atoms in 5 originate from both air and water. The dependence on the metals, compared with FeCl3 ⋅6 H2 O leading to a stable triheteroarylmethyl radical, is quite astounding, which could be attributed to the different oxidation states of the metals and coordination modes confirmed by DFT calculations. This metal and valence dependent process is a very useful way for selectively obtaining these large molecules, which are unachievable by common organic synthesis.

Rare-Earth Metal Tetrathiafulvalene Carboxylate Frameworks as Redox-Switchable Single-Molecule Magnets.

Using the redox-active tetrathiafulvalene tetrabenzoate (TTFTB4- ) as the linker, a series of stable and porous rare-earth metal-organic frameworks (RE-MOFs), [RE9 (µ3 -OH)13 (µ3 -O)(H2 O)9 (TTFTB)3 ] (1-RE, where RE=Y, Sm, Gd, Tb, Dy, Ho, and Er) were constructed. The RE9 (µ3 -OH)13 (µ3 -O) (H2 O)9 ](CO2 )12 clusters within 1-RE act as segregated single-molecule magnets (SMMs) displaying slow relaxation. Interestingly, upon oxidation by I2 , the S=0 TTFTB4- linkers of 1-RE were converted into S= 1 / 2 TTFTB.3- radical linkers which introduced exchange-coupling between SMMs and modulated the relaxation. Furthermore, the SMM property can be restored by reduction in N,N-dimethylformamide. These results highlight the advantage of MOFs in the construction of redox-switchable SMMs.

Retention of a Four-Fold Interpenetrating Cadmium-Organic Framework through a Three-Step Single Crystal Transformation.

Controlled hydration leads to four derivatives of a metal-organic framework consisting of cadmium ions, N1,N1,N4,N4-tetrakis(4-(pyridin-4-yl)phenyl)benzene-1,4-diamine, and coordinated and free nitrates. The balance of water coordination and the multitude of bonding of the weakly coordinated nitrate lead to a progressive change in the coordination number of the Cd2+ ions from eight to seven to six without great perturbation to the 4-fold interpenetration three-dimensional framework.

Silica-Organometallic One-Dimensional Hybrid Employing a Ag-πC═C Bond Connecting Alternating Ag4(NO3)4 and Octavinylsilsesquioxane.

Layering AgNO3 in alcohol onto octavinylsilsesquioxane (OVS) in CHCl3 results in a one-dimensional coordination polymer, {Ag4(NO3)4(OVS)·solvents}n (SD/Ag4a-d), consisting of unprecedented flat weakly bonded Ag4(NO3)4 alternating with the firmly covalent OVS through AgI-πC═C bonds. The preferential assembling medium for SD/Ag4a is proven to be alcohols, where a 4:1 silver-OVS adduct is detected by electrospray ionization mass spectrometry. The present outcomes may assist our knowledge of particular interactions for supramolecular architectures of a polynuclear silver system built from OVS containing eight pendent olefin tails.

Discrete Heteropolynuclear Yb/Er Assemblies: Switching on Molecular Upconversion Under Mild Conditions.

The salts {[Ln2 Ln*(Hhmq)3 (OAc)3 (hfac)2 ]+ [Ln*(hfac)3 (OAc)(MeOH)]- } (Hhmq=2-methanolquinolin-8-oxide, hfac=hexafluoroacetylacetonate; Ln, Ln*=Er, Gd, Yb) feature a discrete heteronuclear cation consisting of two types of lanthanide atoms. The quinolinoxy O-atom serves as a µ2 -bridge to two Ln atoms and as a µ3 -bridge to all three atoms, with metal⋅⋅⋅metal distances being around 3.7 Å. For 1 ([Yb2 Er]+ ), near-infrared downshifted luminescence is switched to competitive upconversion luminescence upon irradiation by a 980 nm laser under an extremely low excitation power (0.288 W cm-2 ) through introduction of fluoride ions. The stability of 1 after addition of fluoride was confirmed by powder X-ray diffraction and multistage mass spectrometry, associated with the 1 H NMR of 6 ([La2 Eu]+ ). More importantly, the at least 20-fold enhancement of the quantum yield in non-deuterated solvents at room temperature under low power densities (2 W cm-2 ) is the highest among the few molecular examples reported.

A Metal-Organic Framework Based on a Nickel Bis(dithiolene) Connector: Synthesis, Crystal Structure, and Application as an Electrochemical Glucose Sensor.

Functionalizing the redox-active tetrathiafulvalene (TTF) core with groups capable of coordination to metals provides new perspectives on the modulation of architectures and electronic properties of organic-inorganic hybrid materials. With a view to extending this concept, we have now synthesized nickel bis(dithiolene-dibenzoic acid), [Ni(C2S2(C6H4COOH)2)2], which can be considered as the inorganic analogue of the organic tetrathiafulvalene-tetrabenzoic acid (H4TTFTB). Likewise, [Ni(C2S2(C6H4COOH)2)2] is a redox-active linker for new functional metal-organic frameworks, as demonstrated here with the synthesis of [Mn2{Ni(C2S2(C6H4COO)2)2}(H2O)2]·2DMF, (1, DMF = N,N-dimethylformamide). 1 is isomorphic to the reported [Mn2(TTFTB)(H2O)2] (2) but is a better electrochemical glucose sensor due to the multiple oxidation-reduction states of the [NiS4] core, which allow glucose to be oxidized to glucolactone by the high oxidation state [NiS4] center. As a non-enzymatic glucose sensor, 1 on Cu foam (CF), 1-CF, was synthesized by a one-step hydrothermal method and exhibited an excellent electrochemical performance. The fabricated 1-CF electrode offers a high sensitivity of 27.9 A M-1 cm-2, with a wide linear detection range from 2.0 × 10-6 to 2.0 × 10-3 M, a low detection limit of 1.0 × 10-7 M (signal/noise = 3), and satisfactory stability and reproducibility.

In Situ Metal-Assisted Ligand Modification Induces Mn4 Cluster-to-Cluster Transformation: A Crystallography, Mass Spectrometry, and DFT Study.

Dehydration of (S,S)-1,2-bis(1H-benzo[d]imidazol-2-yl)ethane-1,2-diol (H4 L) to (Z)-1,2-bis(1H-benzo[d]imidazol-2-yl)ethenol) (H3 L') was found to be metal-assisted, occurs under solvothermal conditions (H2 O/CH3 OH), and leads to [MnII 4 (H3 L)4 Cl2 ]Cl2 ⋅5 H2 O⋅5 CH3 OH (Mn4 L4 ) and [MnII 4 (H2 L')6 (µ3 -OH)]Cl⋅4 CH3 OH⋅H2 O (Mn4 L'6 ), respectively. Their structures were determined by single-crystal XRD. Extensive ESI-MS studies on solutions and solids of the reaction led to the proposal consisting of an initial stepwise assembly of Mn4 L4 from the reactants via [MnL] and [Mn2 L2 ] below 80 °C, and then disassembly to [MnL] and [MnL2 ] followed by ligand modification before reassembly to Mn4 L'6 via [MnL'], [MnL'2 ], and [Mn2 L'3 ] with increasing solvothermal temperature up to 140 °C. Identification of intermediates [Mn4 Lx L'6-x ] (x=5, 4, 3, 2, 1) in the process further suggested an assembly/disassembly/in situ reaction/reassembly transformation mechanism. These results not only reveal that multiple phase transformations are possible even though they were not realized in the crystalline state, but also help to better understand the complex transformation process between coordination clusters during "black-box" reactions.

Copper(II)-Assisted Ligand Fragmentation Leading to Three Families of Metallamacrocycle.

We present an unprecedented copper(II)-assisted organic ligand fragmentation process under basic conditions leading to several ligands within three families of metallamacrocycle, Cu6, Cu8, and Cu16. The sequential multistep reaction include (i) the deprotonation of the starting alcohol, 1,2-bis(3,5-dimethyl-pyrazol-1-yl)ethane-1,2-diol (H2bdped) to its diolate bdped followed by complexation through six bonds (µ6) to three copper atoms in a ring, (ii) the breaking of the ethane-pyrazole C-N bonds by the different solvent alcohols to form 1-(3,5-dimethyl-pyrazol-1-yl)-2-methoxyethane-1,2-diolate (dpmed) or 2-(3,5-dimethyl-pyrazol-1-yl)-2-hydroxyacetate (dpet), while retaining coordination to the copper centers and (iii) the final step to ethane-1,1,2,2-tetraolate, C2H2O44- (et). Importantly, the latter product, only observed on two previous occasions, occupies the core of Cu6 and Cu16 through exceptionally eight coordination bonds (µ8). Its alkyl esters, 2-alkoxyethane-1,1,2-triolate (met, eet, and pet), also occupy the central parts of Cu8 but forming six bonds (µ6) instead. The other product, 3,5-dimethylpyrazolate (dp), acts as peripheral bridges (µ2) but it is not involved in coordination if the starting salt is copper acetate, this may be a consequence of acetate being a better µ2-chelating ligand. In the presence of an oxidizing agent, K2Cr2O7, C2H2O44- (et) is oxidized to oxalate, C2O42- (ox). Thus, an additional µ3-hydroxide and µ4-oxalate in Cu16 widen the complexity of the structures, not to mention the range of coordination geometries of the copper centers, though in the present cases they can be classed in only two types: distorted square-planar and square-pyramid. In addition to single-crystal crystallography, the results from different techniques such as IR, ESI-MS, optical UV-vis, and SQUID magnetometry help in the characterization of these rare metallamacrocycles made from unexpected and in situ generated ligands. We believe the results of the organic transformations are highly relevant to von Liebig's benzil-benzilic acid rearrangement.

Metal-Metalloligand Coordination Polymer Embedding Triangular Cobalt-Oxo Clusters: Solvent- and Temperature-Induced Crystal to Crystal Transformations and Associated Magnetism.

Reaction of the metalloligand IrIII(ppy-COOH)3 and the anisotropic paramagnetic CoII ion under solvothermal conditions resulted in a metal-metalloligand coordination polymer, [CoII3(µ3-O)(µ-OH2){IrIII(ppy-COO)2(ppy-COOH)}2(H2O)4]·2DMF·xH2O (I). It consists of trimeric Co3O secondary building units (SBUs) bridged by pairs of Ir to form chains of alternate orthogonal squares. The compound undergoes two single-crystal to single-crystal transformations while retaining its general structural features. A chemical transformation occurs to give [CoII3(µ3-O){IrIII(ppy-COO)2(ppy-COOH)}2(H2O)4(DMF)]·DMF·H2O (II) by soaking in acetone, where a bridging water molecule departs and the solvent DMF bonds to the vacant site of the Co center. Both I and II undergo a temperature-induced transformation to [CoII3(µ3-O){IrIII(ppy-COO)2(ppy-COOH)}2(H2O)3(DMF)]·DMF (III), where one more coordinated water molecule is lost. The major difference in the three phases is in the Co coordination spheres, which have considerable consequences on the magnetism. Compound I displays paramagnetism down to 2 K, whereas II and III show weak ferromagnetism with TC values of 14 and 17 K, respectively.

Tuning Electrical- and Photo-Conductivity by Cation Exchange within a Redox-Active Tetrathiafulvalene-Based Metal-Organic Framework.

To activate electronic and optical functions of the redox-active metal-organic framework, (Me2 NH2 )[InIII (TTFTB)]⋅0.7 C2 H5 OH⋅DMF (Me2 NH2 @1, TTFTB=tetrathiafulvalene-tetrabenzoate, DMF=N,N-dimethylformamide), has been exchanged by tetrathiafulvalenium (TTF.+ ) and N,N'-dimethyl-4,4'-bipyridinium (MV2+ ). These cations provide electron carriers and photosensitivity. The exchange retains the crystallinity allowing single-crystal to single-crystal post-synthetic transformation to TTF@1 and MV@1. Both TTF.+ and MV2+ enhance the electrical conductivity by a factor of 102 and the visible light induced photocurrent by 4 and 28 times, respectively. EPR evidences synergetic effect involving charge transfer between the framework redox-active TTFTB bridges and MV2+ . The results demonstrate that functionalization of MOF by cation exchange without perturbing the crystallinity extends possibilities to achieve switchable materials.

In Situ Pyrolysis Tracking and Real-Time Phase Evolution: From a Binary Zinc Cluster to Supercapacitive Porous Carbon.

The in situ tracking of the pyrolysis of a binary molecular cluster [Zn7 (µ3 -CH3 O)6 (L)6 ][ZnLCl2 ]2 is presented with one brucite disk and two mononuclear fragments (L=mmimp: 2-methoxy-6-((methylimino)-methyl)phenolate) to porous carbon using TG-MS from 30 to 900 °C. Following up the spilled gas product during the decomposed reaction of zinc cluster along the temperature rising, and in conjunction with XRD, SEM, BET and other materials characterization, where three key steps were observed: 1) cleavage of the bulky external ligand; 2) reduction of ZnO and 3) volatilization of Zn. The real-time-dependent phase-sequential evolution of the remaining products and the processing of pore forming template transformation are proposed simultaneously. The porous carbon structure featuring a uniform nano-sized pore distribution synthesized at 900 °C with the highest surface area of 1644 m2 g-1 and pore volume of 0.926 cm3 g-1 exhibits the best known capacitance of 662 F g-1 at 0.5 A g-1 .

Chalcogens-Induced Ag6Z4@Ag36 (Z = S or Se) Core-Shell Nanoclusters: Enlarged Tetrahedral Core and Homochiral Crystallization.

Control over core structure is much more challenging than that over shell structure in core-shell silver nanoclusters. Herein, two isostructural chalcogen-mediated [Ag6Z4@Ag36] (Z = S or Se) nanoclusters (SD/Ag42a and SD/Ag42b) caging tetrahedral [Ag6Z4] as cores were synthesized by introducing Ph3CSH or Ph3PSe as slow-release source of S2- or Se2-, respectively, and characterized by single-crystal X-ray diffraction (SCXRD). As compared to the previously reported [AgS4@Ag36] cluster (Ag37), we found that introducing additional S2- or Se2- ions can effectively enlarge the inner core from tetrahedral AgS4 to Ag6Z4, which is a regular octahedron of silver with four Z2- capping on one tetrahedral set of four faces. More interestingly, the molecular enantiomers of SD/Ag42a and SD/Ag42b segregate into different crystals (P212121), while those of Ag37 form racemic crystals (I41/acd). The larger Ag6Z4 core in Ag42 clusters also extends their emission to the near-infrared region (∼760 nm). The study confirms that chalcogenide can enlarge the nuclearity of nanoclusters by altering the inner core structure and affords a new strategy to synthesize chiral core-shell silver nanoclusters of higher-order in controlled fashion.

Thermally Induced trans-to-cis Isomerization and Its Photoinduced Reversal Monitored using Absorption and Luminescence: Cooperative Effect of Metal Coordination and Steric Substituent.

For ethene derivatives with large groups the cis-isomer is often quite unstable and unavailable. Herein, we report an exception of two stable coordination complexes, (cis-L)ZnCl2 , starting from trans-1,2-bis(1-R-benzo[d]imidazol-2-yl)ethene (R=H, L1; R=CH3 , L2) ligands under solvothermal condition (T ≥140 °C). Using the intensity of the absorption and luminescence spectra as probes we proposed its progressive cis-to-trans reversal upon irradiation with UV light, which was confirmed by powder X-ray diffraction (PXRD). Similar results observed in the series of (cis-L2)MII Cl2 [M=Fe (4), Co (5), Ni (6)] demonstrate the universal strategy. The results of PXRD, NMR spectroscopy, ESI-MS and DFT calculations support the above conclusion. NMR spectroscopy indicates that irradiation of 1 converts an optimized 71 % of the cis-isomer to trans, whereas the free trans-L1 ligand transforms to only 15 % cis-isomer under similar conditions.

A Chiral and Polar Single-Molecule Magnet: Synthesis, Structure, and Tracking of Its Formation Using Mass Spectrometry.

The solvothermal reaction of cobalt(II) sulfate with S, S-1,2- bis(1-methyl-1 H-benzo[ d]imidazol-2-yl)ethane-1,2-diol, (H2L), neutralized with triethylamine (Et3N) in a mixture of methanol and water (2:1), resulted in triangular red crystals of [CoII7(L)3(SO4)3(OH)2(H2O)9]·4H2O·3CH3OH (Co7). It is formed of chiral and polar clusters crystallizing in the R3 space group. Co7 consists of apex-shared asymmetric dicubane units where all of the metals adopt an octahedral coordination and the three ligands wrap diagonally around the unit. One end of the cluster is bonded by six water molecules and the other end by three monodentate sulfates. The head-to-tail packing through extended H-bonds leads to polar chains. The ligand has lost two protons, adopts a cis-conformation, and is coordinated to five metals around the waist of the dicubane. Electrospray ionization mass spectrometry (ESI-MS) of solutions of the reaction as a function of time reveals the possible step-by-step assembly process of the cluster: the initial product [CoII(HL)(SO4)]2- combines with CoSO4, forming [CoII2(HL)(SO4)2]2-, and then, upon addition of Et3N, dimerizes through a [OH]- bridge to [CoII4(HL)2(OH)(CH3OH)2(SO4)3]- followed by capture of one Co2+ and one CoSO4 to form [CoII6(L)2(OH)(CH3O)(SO4)4]2- before eventually binding to CoL to form [CoII7(L)3(OH)2(SO4)4]2-. These results allow us to propose a possible process for the formation of Co7, which is a good example for chiral multidentate chelating ligand-controlled assembly of clusters. Magnetization measurements as a function of the temperature, field, and ac-frequency reveal ferromagnetic coupled moments and single-molecule magnetism (SMM).

Difference in the Formation of Two Structural Types of V-Shaped MII3 Clusters: Diffraction, Mass Spectrometry, and Magnetism.

A way to understand kinetics and explore mechanism of reactions is to identify the intermediates and their relative energetics. In this respect, low-energy electrospray ionization mass spectrometry is providing information on possible intermediates that can be tandemly verified using crystallography of the products. This has been extended to the study of the formation of functional clusters of transition metals under varying conditions. The reaction of NiL2 (L = 2-ethoxy-6-( N-methyliminomethyl)phenolate) with MII(H2O)6(ClO4)2 in the presence of Et3N base leads to [Ni xM7- x(µ3-OH)6L6]2+ according to NiL2 → [M2L3]+ → [M4(OH)2L4]2+ → [M7(OH)6L6]2+. In contrast, its reaction with MII(H2O)6(NO3)2 in the absence of base leads to two crystallographic structural types [MII3L4(NO3)2(H2O)2]·CH3CN for M = Ni (I-Ni3) or Co (I-Co xNi3- x, x = 0-3) and [MIINiII2L4(NO3)2] for M = Zn (II-ZnNi2) or Co (II-CoNi2). Interestingly, ESI-MS suggests three slightly different formation processes: for I-Ni3, {NiL2 → [Ni2L(NO3)2]+ → [Ni2L2(NO3)]+ → [Ni2L3]+ → [Ni3L4(NO3)]+}; for II-ZnNi2, {NiL2 → [ZnNiL2(NO3)]+ → [ZnNi2L4(NO3)]+}; for II-CoNi2 and I-Co xNi3- x, {NiL2 → [M2L2(NO3)]+ → [M2L3]+ → [M3L4(NO3)]+}. Magnetization measurements reveal the site of each metal ionin II-ZnNi2 and the number of single electrons within different clusters. Without the base, there is an interplay between the weak coordinating nitrate and water stabilizing the two structural types via the different formation processes. The results indicate that not only the strength of the ligand matters but also the ionic sizes and possibly softness of the metals may be implicated.

Carbon Dioxide (CO2) Fixation: Linearly Bridged Zn2 Paddlewheel Nodes by CO2 in a Metal-Organic Framework.

When the reaction of zinc nitrate with 4',4‴,4‴″,4‴‴'-(ethene-1,1,2,2-tetrayl)tetrakis[(1,1'-biphenyl-3-carboxylic acid)] (H4tmpe) in dimethylformamide (DMF) under hydrothermal condition is performed in air or carbon dioxide (CO2), [Zn4(tmpe)2(H2O)2(µ2-CO2)]·8DMF·18H2O (1) crystallizes out. However, if it is in dioxygen, argon, or carbon monoxide, [Zn2(tmpe)(DMF)]·2DMF·8H2O (2) is the product. Both compounds are chemically stable coordination polymers. 1 contains zinc carboxylate paddlewheels as nodes linearly bridged by CO2 into two interpenetrating lattices, and 2 has an infinite single framework formed by a tetranuclear node. 1 is the second example containing the linear CO2-bridged paddlewheel node. Interestingly, CO2 fixation in a µ2-η2O,O bridging mode is observed in 1, which is rarely characterized structurally and has been confirmed using IR and gas chromatography analysis. The stability of 1 is further verified by density functional theory calculations, which found an energy minimum with a Zn-O═C angle of 180°. Both compounds display strong emission around 490 nm and excited-state lifetimes around 2.4 ns.

Hexadecanuclear MnII2MnIII14 Molecular Torus Built from in Situ Tandem Ligand Transformations.

A mixed-valent hexadecanuclear manganese cluster, [MnII2MnIII14(trz)14(thetach)4(µ3-O)8(H2O)10](ClO4)6 (Mn16), containing two MnII and 14 MnIII ions, is constructed from mixed in situ generated ligands, 1,2,3-triazole (Htrz) and 1,3,5-tri(2-hydroxyethyl)-1,3,5-triazacyclohexane (H3thetach). Remarkably, both ligands were not initially added into the reaction system, and their formations involve the in situ ligand decomposition and subsequent condensation reactions. The core of Mn16 is an elongated torus comprised of eight Mn atoms and four [Mn2O2] subunits bridged by oxo or alkoxide. The high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) of Mn16 dissolved in CH3CN indicates its structure remains intact as +3 and +4 species. Temperature and field dependent magnetization revealed predominantly antiferromagnetic exchange interactions within the cluster. The work provides one-pot synthesis of high-nuclearity manganese clusters using the ligands generated by in situ reactions in a tandem fashion.

Two- and Three-Dimensional Heterometallic Ln[Ru2-α-Ammonium Diphosphonate] Nets: Structures, Porosity, Magnetism, and Proton Conductivity.

By virtue of its magnetic moment and variable valencies, the D4h paddlewheel ruthenium dimer is a desirable molecular building block for the construction of functional networks. If in addition to the Ru open axial site the organic ligand is designed to allow transversal connections, a wider range of structural possibilities is expected. The organic ligand can also be modified to introduce other functionalities. In the present study we employed a diphosphonate containing a protonated amine, 1-ammoniummethylenediphosphonate [NH3CH(PO3)23-; (Hamdp)], as the ligand to construct paddlewheel Ru2(Hamdp)2 building block. Three networks of different structural dimensionalities were obtained. (H3O)2[RuII2(Hamdp)2] (1) forms one-dimensional chain of S = 1 RuII2 bridged at axial positions through Ru-O bonds. From 1 as a starting material, its reaction with lanthanide ions results in the bimetallic Dy(H2O)3[Ru2(Hamdp)2][Ru2(Hamdp)2(H2O)2][Ru2(Hamdp)(amdp)]0.5·12H2O (2), which has a pillared-bilayer structure and Yb[Ru2(Hamdp)2]2[Ru2(Hamdp)2(H2O)2]·15H2O (3), which is a three-dimensional open framework, both contain mixed-valent RuII/III2 units and show new connection topologies of the Ru2 dimers. After activation 2 does not adsorb N2 and CO2 but takes up 12 H2O. In contrast, 3 take up all three gases. The optimum proton conductivities were moderate reaching 1.44 × 10-6 for 2 and 0.93 × 10-5 S cm-1 for 3 at 95% relative humidity and 55 °C.