Synthesis, Crystal Structures, and Photochemical Properties of a Family of Heterometallic Titanium Oxo Clusters.

The incorporation of heterometallic atoms into the structure of titanium-oxygen nanomaterials is one of the known and effective strategies to develop new high-performance photovoltaic active materials. In this study, we have synthesized three benzoic acid-stabilized heterometallic titanium oxo clusters with the different transition metals Co, Cu, and Cd, formulated as [Ti4Co2(µ2-O)2(µ3-O)2(C6H5COO)12(CH3CN)2]·2CH3CN (1), [Ti5Cu4(µ3-O)6(C6H5COO)16] (2), and [Ti12Cd5(µ2-O)(µ3-O)15(µ4-O)2(C6H5COO)22(C6H5COOH)(CH3CN)]·CH3CN·C6H5COOH (3), and then we characterized their structures. UV-vis spectroscopy analysis revealed an enhanced UV-vis-light absorption of those heterometallic clusters. The density functional theory calculations indicated that charge transfer occurs from the p orbital of O atoms to the d orbital of Ti atoms in the TiO core (O → Ti) as well as from the metal to the core in 1 and 2. We also measured the photocurrent response and photocatalytic H2 evolution, which shows enhancement in the photocurrent intensity and good H2 evolution ability because of the cooperative effect of heterometal doping in titanium oxo clusters.

Designed Cluster Assembly of Multidimensional Titanium Coordination Polymers: Syntheses, Crystal Structure and Properties.

The exploitation of new titanium-based coordination polymers (Ti CPs) with high crystallinity is difficult but highly desirable for their potential applications in photocatalysis. Herein, a cluster-cooperative assemble strategy is developed to synthesize Ti CPs. By utilizing various bifunctional ligands containing carboxylate acids and N-donor groups, we successfully assembled the zero-dimensional (0D) [(Ti3 O)(iPrO)8 ]2+ or [(Ti4 O2 )(iPrO)6 ]6+ clusters into one-dimensional (1D) tube-, ribbon-, or helical chain-shape architectures, two-dimensional (2D) layered structures, and a rare parallel 2D→three-dimensional (3D) polycatenation framework with various copper iodide dopants, including rhombus- or wing-shaped Cu2 I2 and tetrahedron- or ladder-shaped Cu4 I4 . The as-synthesized compounds display strong absorption in the visible region with narrow band gaps ranging from 1.70 to 2.72 eV and exhibit good photocatalytic activities in the degradation of organic pollutants.

[Co2 @Ge16 ]4- : Localized versus Delocalized Bonding in Two Isomeric Intermetalloid Clusters.

We report the successful isolation and structural elucidation of two bimetallic doped [Co2 @Ge16 ]4- clusters (α and ß form), which were synthesized through the reaction of [{(ArN)2 CtBu}Co(η6 -toluene)] (Ar=2,6-diisopropylphenyl) and K4 Ge9 in ethylenediamine (en) solution and co-crystallized together in [K(2,2,2-crypt)]4 [Co2 @Ge16 ]⋅en. The α-[Co2 @Ge16 ]4- isomer prefers a distinct D2h 3-connected architecture, whereas the deltahedral isomeric ß-[Co2 @Ge16 ]4- isomer adopts a quasi-C2h geometry and can be seen as coupling of two distorted arachno-[Co@Ge10 ] units. Chemical bonding analyses indicate that the skeleton of the α isomer is mainly composed of localized bonds, whereas only multicenter bonding interactions govern the geometry of the ß isomer, which was further found to exhibit a fluxional behavior. The coexistence of both isomers within one unit cell links the 3-connected clusters with their deltahedral congeners, thus highlighting the structural and electronic flexibility of such discreet cluster systems.

Reactivity Studies of [Co@Sn9]4- with Transition Metal Reagents: Bottom-Up Synthesis of Ternary Functionalized Zintl Clusters.

The binary cluster [Co@Sn9]4- (1) was extracted directly from ethylenediamine (en) solutions of an intermetallic precursor with nominal composition "K5Co3Sn9", and its reactions with various organometallic reagents were explored. Reaction with Ni(PPh3)2(CO)2 gives [Co@Sn9Ni(CO)]3- (2), a Co-centered closo-Sn9Ni bicapped square antiprism. Analogous reactions with Ni(COD)2, Pt(PPh3)4, and Au(PPh3)Ph led to the isolation of [Co@Sn9Ni(C2H4)]3- (3), [Co@Sn9Pt(PPh3)]3- (4), and [Co@Sn9AuPh]3- (5), respectively. 3 is structurally similar to 2 but significantly distorted from a closo-cluster with one open square face. The coordination of [CoSn9]3- by PtPPh3 (4) or AuPh (5) induces a structural transformation in the CoSn9 core, from a monocapped square antiprism ( C4 v) to a tricapped trigonal prismatic structure ( pseudo- C3 v), with the transition metal fragment capping a triangular face. The four trimetallic anions presented here represent a new family of ternary functionalized Zintl clusters incorporating a d9 transition metal center. All clusters were characterized by single-crystal X-ray diffraction and electrospray ionization mass spectrometry (ESI-MS).

Construction of Uranyl Organic Hybrids by Phosphonate and in Situ Generated Carboxyphosphonate Ligands.

The hydrothermal reaction of uranyl ions with (5-methyl-1,3-phenylene)diphosphonic acid (H4MPDP) in the presence of additives such as nitric acid, N-bearing species, and heterometal ions yielded five new uranyl organic hybrids: (H3O)[(UO2)5(H2O)4(H3DPB)2(H2DPB)(HDPB)]·2H2O (1), (Hphen)(phen)[(UO2)3(H2DPB)(HDPB)] (2), (H2dipy)[(UO2)3(MPDP)2] (3), Zn(bipy)(UO2)(MPDP) (4), and Co(bipy)(UO2)(MPDP)·H2O (5) (H5DPB = 3,5-diphosphonobenzoic acid; phen = 1,10-phenanthroline; dipy = 4,4'-bipyridine; bipy = 2,2'-bipyridine). Single-crystal X-ray diffraction (XRD) demonstrates that 1 and 2 are 3D frameworks constructed of uranyl centers and carboxyphosphonate DPB ligands; the latter were formed via the in situ oxidation of H4MPDP. In the homometallic uranyl diphosphonate 3, less common UO6 square bipyramids connected by MPDP ligands were incorporated to form the 2D assembly. A further introduction of heterometal ions produced two heterobimetallic uranyl phosphonates 4 and 5. Both of them show layered structures, formed by UO6 square bipyramids linked by MPDP ligands with heterometal-centered polyhedra decorated on the sides of the layers. It is found that the pH and heterometal ions have significant effects on the structures of the complexes. In addition to the syntheses and XRD characterization, the spectroscopic properties of these uranyl complexes were also addressed. To complement the experimental results, density functional theory calculations were carried out on several model complexes that feature a homo- or heterobimetallic molecular skeleton. Geometrical/electronic structures, IR spectra, and electronic absorptions were discussed.

A Multifunctional Mn(II) Phosphonate for Rapid Separation of Methyl Orange and Electron-Transfer Photochromism.

A Mn(II) phosphonate of the general formula [Mn(H2 L)2 (H2 O)2 (H2 bibp)] adopts a layered motif with protonated H2 bibp(2+) cations embedded in the channels (H4 L=thiophene-2-phosphonic acid; bibp=4,4'-bis(1-imidazolyl)biphenyl). The title compound exhibits excellent adsorptive removal of methyl orange (MO) dye from aqueous solution. Its advantageous features include fast adsorption, high uptake capacity, selective removal, and reusability, which are of great significance for practical application in wastewater treatment. Meanwhile, the compound displays rapid photochromism upon irradiation with visible light at room temperature. Extensive research has demonstrated that such behavior is based on a ligand-to-ligand charge-transfer (LLCT) mechanism. The irradiated sample possesses an ultra-long-lived charge-separated state. Moreover, not only is the compound the first Mn-based photochromic MOF, but it is also one of the very few examples showing LLCT with non-photochromic components.

Particular Handedness Excess through Symmetry-Breaking Crystallization of a 3D Cobalt Phosphonate.

A 3D chiral cobalt phosphonate has been obtained from achiral precursors in the absence of chiral inducers. Remarkably, the bulk sample is largely enantio-enriched with particular handedness through symmetry-breaking crystallization in spite of multiple repeated experiments. Moreover, protonation of this chiral material introduces Brønsted acid sites, the structure of which is unique to the heterogeneous phase for the ring opening of epoxies.

Regioisomer-specific electron affinities and electronic structures of C70para-adducts at polar and equatorial positions with (bromo)benzyl radicals: photoelectron spectroscopy and theoretical study.

Negative ion photoelectron spectroscopy shows interesting regioisomer-specific electron affinities (EAs) of 2,5- and 7,23-para-adducts of C70 [(ArCH2)2C70] (Ar = Ph, o-, m-, and p-BrC6H4). Their EA values are larger than that of C70 by 5-150 meV with the 2,5-polar adducts' EAs being higher than their corresponding 7,23-equatorial counterparts, exhibiting appreciable EA tunable ranges and regioisomeric specificity. Density functional theory (DFT) calculations reproduce both the experimental EA values and EA trends very well.

All-Metal Antiaromaticity in Sb4 -Type Lanthanocene Anions.

Antiaromaticity, as introduced in 1965, usually refers to monocyclic systems with 4n π electrons. This concept was extended to all-metal molecules after the observation of Li3 Al4 (-) in the gas phase. However, the solid-phase counterparts have not been documented to date. Herein, we describe a series of all-metal antiaromatic anions, [Ln(η(4) -Sb4 )3 ](3-) (Ln=La, Y, Ho, Er, Lu), which were isolated as the K([2.2.2]crypt) salts and identified by single-crystal X-ray diffraction. Based on the results obtained from the chemical bonding analysis, multicenter indices, and the electron-counting rule, we conclude that the core [Ln(η(4) -Sb4 )3 ](3-) fragment of the crystal has three locally π-antiaromatic Sb4 fragments. This complex represents the first locally π-antiaromatic all-metal system in the solid state, which is stabilized by interactions of the three π-antiaromatic units with the central metal atom.

Peculiar All-Metal σ-Aromaticity of the [Au2 Sb16 ]4- Anion in the Solid State.

Gas-phase clusters are deemed to be σ-aromatic when they satisfy the 4n+2 rule of aromaticity for delocalized σ electrons and fulfill other requirements known for aromatic systems. While the range of n values was shown to be quite broad when applied to short-lived clusters found in molecular-beam experiments, stability of all-metal cluster-like fragments isolated in condensed phase was previously shown to be mainly ascribed to two electrons (n=0). In this work, the applicability of this concept is extended towards solid-state compounds by demonstrating a unique example of a storable compound, which was isolated as a stable [K([2.2.2]crypt)]+ salt, featuring a [Au2 Sb16 ]4- cluster core possessing two all-metal aromatic AuSb4 fragments with six delocalized σ electrons each (n=1). This discovery pushes the boundaries of the original idea of Kekulé and firmly establishes the usefulness of the σ-aromaticity concept as a general idea for both small clusters and solid-state compounds.

An All-Metal Aromatic Sandwich Complex [Sb3Au3Sb3](3-).

A sandwich complex, as exemplified by ferrocene in the 1950s, usually refers to one metal center bound by two arene ligands. The subject has subsequently been extended to carbon-free aromatic ligands and multiple-metal-atom "monolayered" center, but not to an all-metal species. Here, we describe the synthesis of an unprecedented all-metal aromatic sandwich complex, [Sb3Au3Sb3](3-), which was isolated as K([2.2.2]crypt)(+) salt and identified by single-crystal X-ray diffraction. Quantum chemical calculations indicate that intramolecular electron transfers for the three metallic layers (Sb → Au donation and Sb ← Au back-donation) markedly redistribute the valence electrons from the cyclo-Sb3 ligands and Au3 interlayer to the Au-Sb bonds, which hold the complex together via σ bonding. Each cyclo-Sb3 possesses aromaticity with delocalized three-center three-electron (3c-3e) π bonds, which are essentially equivalent to a 3c-4e ππ* triplet system, following the reversed 4n Hückel rule for aromaticity in a triplet state.

Accurate assembly of ferrocene-functionalized {Ti22Fc4} clusters with photocatalytic amine oxidation activity.

We report here the synthesis of a ferrocene-functionalized {Ti22Fc4} cluster with a 'dimer-of-clusters' topology, which represents the largest Ti-oxo cluster (TOC) modified with organometallic groups ever reported. The exact assembly path of {Ti22Fc4} can be inferred from its two substructures, {Ti11Fc2} and {Ti5Fc}, which can also be synthesized independently through subtle changes in reaction conditions. Furthermore, we used these clusters as photocatalysts, and have studied, for the first time, the photocatalytic activity of TOCs in the oxidative coupling of amines.

Monocarboxylate-driven structural growth in Calix[n]arene-polyoxotitanate hybrid systems: utility in hydrogen production from water.

A carboxylate-driven assembly strategy has been developed for the first time to build calix[n]arene-based polyoxotitanate clusters with tuneable nuclearity and structures. Photocatalytic studies revealed that these clusters exhibit structural-dependent H2 evolution ability with a maximum rate up to 415.11 µmol h-1 g-1, which is almost the highest recorded in polyoxotitanate clusters.

3-(1,3-Dithio-lan-2-yl-idene)-1-phenyl-pyridine-2,4(1H,3H)-dione.

The title compound, C(14)H(11)NO(2)S(2), was synthesized by reaction of 2-(1,3-dithio-lan-2-yl-idene)-3-oxo-N-phenyl-butanamide with N,N'-dimethyl-formamide dimethyl acetal in N,N'-dimethyl-formamide. The mol-ecule exhibits a V-shaped conformation in the crystal, with a dihedral angle of 65.9 (2)° between the benzene and pyridine rings. In the crystal. C-H⋯O and C-H⋯S interactions are observed. Two C atoms of the dithiolane ring are disordered with occupancies in the ratio 0.541 (13)/0.459 (13).

Synthesis and structure of a family of rhodium polystannide clusters [Rh@Sn10]3-, [Rh@Sn12]3-, [Rh2@Sn17]6- and the first triply-fused stannide, [Rh3@Sn24]5.

Through relatively subtle changes in reaction conditions, we have been able to isolate four distinct Rh/Sn cluster compounds, [Rh@Sn10]3-, [Rh@Sn12]3-, [Rh2@Sn17]6- and [Rh3@Sn24]5-, from the reaction of K4Sn9 with [(COE)2Rh(µ-Cl)]2(COE = cyclooctene). The last of these has a hitherto unknown molecular topology, an edge-fused polyhedron containing three Rh@Sn10 subunits, and represents the largest endohedral Group 14 Zintl cluster yet to have been isolated from solution. DFT has been used to place these new species in the context of known cluster chemistry. ESI-MS experiments on the reaction mixtures reveal the ubiquitous presence of {RhSn8} fragments that may play a role in cluster growth.

Correction: A microporous Cu-MOF with optimized open metal sites and pore spaces for high gas storage and active chemical fixation of CO2.

Correction for 'A microporous Cu-MOF with optimized open metal sites and pore spaces for high gas storage and active chemical fixation of CO2' by Chao-Ying Gao et al., Chem. Commun., 2016, 52, 11147-11150.

[Ge5Ni2(CO)3]2-: the first functionalized cluster of closo-[Ge5]2.

A new functionalized cluster, [Ge5Ni2(CO)3]2-, derived from the closo-[E5]2- (E = Si-Pb) anions which have been known for decades but whose reactivity has rarely been studied, was successfully isolated from the reaction of [Ni(PPh3)2(CO)2] and [Ge5]2- in ethylenediamine (en) solution, and its formation pathway was also investigated.

A microporous Cu-MOF with optimized open metal sites and pore spaces for high gas storage and active chemical fixation of CO2.

A microporous Cu-MOF with optimized open metal sites and pore space was constructed based on a designed bent ligand; it exhibits high-capacity multiple gas storage under atmospheric pressure and efficient catalytic activity for chemical fixation of CO2 under mild conditions.

A niobium-necked cluster [As3Nb(As3Sn3)](3-) with aromatic Sn3(2-) .

We describe here the synthesis and characterization of a ternary cluster compound [As3Nb(As3Sn3)](3-) (1), in which a niobium(v) atom is coordinated by an As3(3-) triangle and a bowl-type As3Sn3(5-) ligand. Cluster 1 was synthesized by dissolving K8NbSnAs5 (2) in the presence of [2.2.2]crypt in ethylenediamine solution, filtered and layered with toluene, then crystallized in the form of [K([2.2.2]crypt)]3[As3Nb(As3Sn3)]·en·tol. The flower-vase shaped compound 1 features a new structure type, rather different from the known Zintl phases. The stability and bonding of 1 are elucidated via extensive bonding analyses. The Sn3 ring is found to have σ-aromaticity featuring a delocalized Sn-Sn-Sn σ bond. Electronic structure calculations confirm the Nb(v) oxidation state and weak Nb-Sn and Sn-Sn bonding, in addition to the normal Nb-As and As-As bonds.