Topotactic Conversion of Titanium-Oxo Clusters to a Stable TOC-Based Metal-Organic Framework with the Selective Adsorption of Cationic Dyes.

Titanium-oxo cluster (TOC)-based metal-organic frameworks (MOFs) have received considerable attention in recent years due to their ability to expand the application of TOCs to fields that require highly stable frameworks. Herein, a new cyclic TOC formulated as [Ti6O6(OiPr)8(TTFTC)(phen)2]2 (1, where TTFTC = tetrathiafulvalene tetracarboxylate and phen = phenanthroline) was crystallographically characterized. TOC 1 takes a rectangular ring structure with two phen-modified Ti6 clusters as the width and two TTFTC ligands as the length. An intracluster ligand-to-ligand (TTF-to-phen) charge transfer in 1 was found for TOCs for the first time. Compound 1 undergoes topotactic conversion to generate stable TOC-MOF P1, in which the rectangular framework in 1 formed by a TOC core and ligands is retained, as verified by comprehensive characterization. P1 shows an efficient and rapid selective adsorption capacity for cationic dyes. The experimental adsorption capacity (qex) of P1 reaches a value of up to 789.2 mg/g at 298 K for the crystal violet dye, which is the highest among those of various adsorbents. The calculated models are first used to reveal the structure-property relationship of the cyclic host to different guest dyes. The results further confirmed the host MOF structure of P1.

Redox-Active Two-Dimensional Tetrathiafulvalene-Copper Metal-Organic Framework with Boosted Electrochemical Performances for Supercapatteries.

Metal-organic frameworks (MOFs) have attracted noticeable attention as promising candidates for electrochemical energy storage. However, the lack of electrical conductivity and the weak stability of most MOFs result in poor electrochemical performances. Here, a tetrathiafulvalene (TTF)-based complex, formulated as [(CuCN)2(TTF(py)4)] (1) (TTF-(py)4 = tetra(4-pyridyl)-TTF), is assembled by in situ generation of coordinated CN- from a nontoxic source. Single-crystal X-ray diffraction analysis reveals that compound 1 possesses a two-dimensional layered planar structure, which is further stacked in parallel to form a three-dimensional supramolecular framework. The planar coordination environment of 1 is the first example of a TTF-based MOF. Attributed to the unique structure and redox TTF ligand, the electrical conductivity of 1 is significantly increased by 5 orders of magnitude upon iodine treatment. The iodine-treated 1 (1-ox) electrode displays typical battery-type behavior through electrochemical characterizations. The supercapattery based on the 1-ox positrode and AC negatrode presents a high specific capacity of 266.5 C g-1 at a specific current of 1 A g-1 with a remarkable specific energy of 62.9 Wh kg-1 at a specific power of 1.1 kW kg-1. The excellent electrochemical performance of 1-ox is one of the best among those reported supercapatteries, demonstrating a new strategy for developing MOF-based electrode materials.

Oxidatively Doped Tetrathiafulvalene-Based Metal-Organic Frameworks for High Specific Energy of Supercapatteries.

Poor electrical conductivity and instability of metal-organic frameworks (MOFs) have limited their energy storage and conversion efficiency. In this work, we report the application of oxidatively doped tetrathiafulvalene (TTF)-based MOFs for high-performance electrodes in supercapatteries. Two isostructural MOFs, formulated as [M(py-TTF-py)(BPDC)]·2H2O (M = NiII (1), ZnII (2); py-TTF-py = 2,6-bis(4'-pyridyl)TTF; H2BPDC = biphenyl-4,4'-dicarboxylic acid), are crystallographically characterized. The structural analyses show that the two MOFs possess a three-dimensional 8-fold interpenetrating diamond-like topology, which is the first example for TTF-based dual-ligand MOFs. Upon iodine treatment, MOFs 1 and 2 are converted into oxidatively doped 1-ox and 2-ox with high crystallinity. The electrical conductivity of 1-ox and 2-ox is significantly increased by six∼seven orders of magnitude. Benefiting from the unique structure and the pronounced development of electrical conductivity, the specific capacities reach 833.2 and 828.3 C g-1 at a specific current of 1 A g-1 for 1-ox and 2-ox, respectively. When used as a battery-type positrode to assemble a supercapattery, the AC∥1-ox and AC∥2-ox (AC = activated carbon) present an energy density of 90.3 and 83.0 Wh kg-1 at a power density of 1.18 kW kg-1 and great cycling stability with 82% of original capacity and 92% columbic efficiency retention after 10,000 cycles. Ex situ characterization illustrates the ligand-dominated mechanism in the charge/discharge processes. The excellent electrochemical performances of 1-ox and 2-ox are rarely reported for supercapatteries, illustrating that the construction of unique highly dense and robust structures of MOFs followed by postsynthetic oxidative doping is an effective approach to fabricate MOF-based electrode materials.

Photocurrent and Gelation Properties of Polyphenol-Modified Titanium-Oxo Compounds.

Organic-inorganic hybrid metal-polyphenols as stable structural modules have gained extensive interest due to their diverse applications. However, titanium-oxo compounds (TOCs) with large molecular polyphenols have been less explored, and they were expected to be different from small polyphenols with isolated metal ions. Herein, 4-methyl-esculetin (Mesc), a catechol derivative, was selected to construct three TOCs, namely, [Ti17O24(Mesc)4(OiPr)16] (1), [Ti12O14(OiPr)18][Ti16O14(Mesc)12(OiPr)14] (2), and [Ti3O(Mesc)2(OAc)2(OiPr)4] (3). These compounds were structurally characterized. Photocurrent responses were evaluated using the compound-sensitized TiO2 electrodes. It was found that the current densities of 1-3 electrodes are in the order of 1 ≫ 3 > 2, which relates to the ligand-to-TiO core and ligand-to-ligand charge transfers (LMCT and LLCT, respectively). Density functional theory calculations showed that the lowest band gap of 1 originates from its LLCT. Compound 1 reacted with polyphenol tannin (TA) to form a fully transparent and robust gel (1-TA), and the gelation properties were investigated. Using the gel as a nano-TiO2 fixing agent, solar cell electrodes were prepared by a low-temperature wet method. The photocurrent responsive behavior of the 1-TA/TiO2 electrode was compared with that of the 1-sensitized traditional high-temperature-treated TiO2 electrode. Although the current density of the former is somewhat lower than that of the traditional electrode, the low-temperature wet preparation of the 1-TA/TiO2 electrode is more energy-efficient and sustainable.

A Convenient Procedure for Preparing BiOX-TiO2 Photoelectrocatalytic Electrodes from a Titanium-Oxo Compound-Modified Carbon Fiber Cloth.

Photoelectrocatalysis (PEC) has shown great advantages in sustainable organic synthesis and wastewater treatment because the PEC process can minimize electron-hole recombination, thereby improving the photocatalytic performance. Here, we report a convenient procedure for preparing immobilized BiOX-TiO2 photoelectrocatalytic electrodes from a titanium-oxo compound (TOC)-modified carbon fiber cloth (CFC). Crystalline TOCs composed of Ti12 cations and bismuth halide anions, [Ti12O14(OiPr)18][Bi3Br11(THF)2] (1) and [Ti12O14(OiPr)18][Bi4I14(THF)2] (2), were grown on CFC. Taking advantage of the easy hydrolysis of the titanium-oxo cation and bismuth halide anion, we could easily transform these CFC-immobilized crystals into BiOX-TiO2/CFC (X = Br or I) photocatalysts, which facilitates recycling of the catalysts. The photocatalytic dye degradation test showed that the efficiency did not decrease obviously after 10 photocatalytic cycles. Using BiOX-TiO2-modified CFC as electrodes, electrocatalysis (EC), photocatalysis (PC), and PEC were examined. PEC showed an attractive synergistic effect of EC and PC. These TOC-modified CFCs would be potential candidates for catalytic electrodes for sustainable wastewater purification.

A Cyclic Titanium-Oxo Cluster with a Tetrathiafulvalene Connector as a Precursor for Highly Efficient Adsorbent of Cationic Dyes.

Titanium-oxo clusters (TOCs) have been studied for applications in catalysis, energy storage and transfer, light emission, and so on; however, use of TOCs for the selective adsorption of dyes has not yet been reported. Herein, a TOC compound formulated as [Ti6O3(OiPr)14(TTFTC)]4 (1, TTFTC = tetrathiafulvalene-tetracarboxylate) was successfully prepared and crystallographically characterized. Compound 1 has a cyclic structure assembled by four Ti6 clusters and four rodlike TTFTC connectors. Red compound 1 self-condenses to form a black polymeric organic-inorganic hybrid material (denoted as B-1), which was characterized by various techniques. B-1 is an amorphous TiO material that is formed by the irregular condensation of 1 by the removal of alkoxyl groups. B-1 exhibits high dye adsorption efficiency toward cationic dyes with a qe value of 651.3 mg/g at 298 K for methylene blue (MB). Moreover, B-1 can be used to selectively remove MB not only from mixed cationic-anionic dye solutions but also from some mixed cationic dyes, which is related to their structures. Kinetic, isotherm, and thermodynamic studies demonstrated that the pseudo-second-order kinetic model and Freundlich model show a good fit to the experimental data. The adsorption process involves an exothermic and entropy decreasing process. In addition, dye-adsorbed B-1 can be further used as a photocurrent-responsive material. The work opens up a new field for the application of TOCs in the selective adsorption and removal of dyes.

Tetrathiafulvalene-Cobalt Metal-Organic Frameworks for Lithium-Ion Batteries with Superb Rate Capability.

Although pristine metal-organic framework (MOF) anodes for lithium-ion batteries (LIBs) show moderate activities and relatively stable cycling, the poor rate capability of the MOF anodes limited their applications in the development of a new generation of energy storage. Herein, the electric active CoII ion is selected to coordinate with redox-active S-rich tetrathiafulvalene (TTF) derivatives to create two TTF-Co-MOFs, formulated as [Co2(py-TTF-py)2(BDC)2]·2DMF·H2O (TTF-Co-MOF 1) and [Co2(py-TTF-py)2(BPDC)2]·3DMF·3H2O (TTF-Co-MOF 2), where py-TTF-py = 2,6-bis(4'-pyridyl)tetrathiafulvalene, H2BDC = terephthalic acid, H2BPDC = biphenyl-4,4'-dicarboxylic acid, and DMF = N,N-dimethylformamide. Crystallographic characterization indicated that the two MOFs possess similar 2-fold-interpenetrating 3D frameworks but with two different pore sizes. The pore-size-dependent performances of the TTF-Co-MOFs were explored to optimize the MOFs as the anode materials for LIBs. TTF-Co-MOF 1 presents a high reversible specific capacity of 1186.6 mAh g-1 at 200 mA g-1 after 287 cycles. The rate capability is greatly enhanced by the introduction of CoII into TTF-based MOFs with specific capacities of 1028.6 mAh g-1 at 5 A g-1 and 966.5 mAh g-1 at 10 A g-1. On the basis of the series analysis of theoretical calculations, electrochemical impedance spectroscopy, and crystal structures, it is found that the CoII metal centers play a bridging role in charge transport within the MOF framework, which is beneficial for the transportation of Li ions. The competitive performances of TTF-Co-MOF 1 are attributed to the synergistic effect of the CoII metal centers and S-rich TTF ligand as well as suitable porosity. The study shed some light for the fabrication of advanced energy storage devices through the rational design of MOF-based anode materials.

Copper-bipyridine grid frameworks incorporating redox-active tetrathiafulvalene: structures and supercapacitance.

Redox active tetrathiafulvalene (TTF) and its derivatives when used as electrode additives have exhibited improved energy efficiency and sustainability in batteries. However, the structure-property relationship has not been investigated in detail until very recently. In this work, three redox-active TTF compounds were synthesized, and formulated as [Cu(HL)2(bpa)2]n (1), [Cu(bpe)2(H2O)2]n·2n(HL)·nMeOH·nH2O (2), and [Cu(bpp)2(H2O)2]n·2n(HL) (3) (L = dimethylthio-tetrathiafulvalene-bicarboxylate) for this work. The effects of conjugated state and spacer length of the linkers on structural assembly and band gap as well as the interactions of TTF-TTF/TTF-bpy are discussed. Compound 1 is a bpa and HL co-coordinated 1D Cu(ii) polymer. Compounds 2 and 3 are 2D Cu(ii)-bipyridine (4,4) MOFs incorporating HL (1-) as free anion columns. The photocurrent density of 2 is larger than those of 1 and 3 due to a strong charge transfer from TTF to bpe in compound 2. The supercapacitance performances of these compounds were evaluated by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) techniques. The results revealed that the 2D MOF structures of 2 and 3 are beneficial for good specific capacitance values (Csp). This work revealed the structure-property relationships of TTF derivatives for use as electrode active materials in energy transfer and storage.

Mono- and Bismetalphenanthroline-Substituted Ti12 Clusters: Structural Variance and the Effect on Electronic State and Photocurrent Property.

Despite the numerous titanium-oxo clusters (TOCs) which have been reported, the nature of small clusters (nuclearity < 10) as model compounds showed large deviation from that of nanoscale TiO materials. Therefore, theoretical and experimental studies for large TOCs merit more attention. We recently prepared and crystallographically characterized a series of large TOCs: Ti11O15(OiPr)16(Cophen) (1), Ti11O15(OiPr)16(Mnphen) (2), Ti10O14(OEt)16(Mnphen)2 (3), and Ti10O14(OEt)16(Mnphphen)2 (4) (phen = 1,10-phenanthroline, phphen = 4,7-biphenyl-phen). These compounds are derivatives of a Ti12 parent cluster by replacing one or two of the five-coordinated titanium atoms of the Ti12 cluster with a transition metal M, Co(II) and Mn(II), that is chelated by a phen group. The effects of mono- and bis-substituted Mphen on the charge and structure of the clusters are discussed. Theoretical evaluation of the frontier orbitals of the clusters is carried out on the basis of the precisely defined crystal structures. Different from the dye molecule to TiO core charge transfer for the dye-modified TOCs, charge transfer in these clusters is from TiO/TiOM to phen/Mphen. The effects of different metal ions and the number of substituted Mphen moieties on the photocurrent properties are evaluated. The results will be of interest to research on cluster chemistry, especially on the TOC chemistry.

Assembly of a Titanium-Oxo Cluster and a Bismuth Iodide Cluster, a Single-Source Precursor of a p-n-Type Photocatalyst.

Titanium oxides and bismuth halides or oxyhalides have been known to be excellent semiconductors with both excellent photocatalytic and photoelectric properties. The design of supersalts assembled by titanium-oxo clusters (TOCs) and bismuth iodide clusters is a hopeful strategy for exploring the chemistry and application of new titanium-oxo clusters. We report herein a series of unusual ionic TOCs with Ti12 oxo cluster cations and bismuth iodide anions, [Ti12O15(OiPr)17]3[Bi3I12] (Bi3), [Ti12O14(OiPr)18][Bi4I14(THF)2] (Bi4), and [Ti12O14(OiPr)18][Ti11BiO14(OiPr)17][Bi6I22] (Bi6). Single-crystal X-ray analysis revealed that the type and charge of the Ti12 clusters varied with the charges of different bismuth iodide clusters. Taking advantage of the easy hydrolysis of the TOCs and BiI clusters in water, we used these supersalt crystals as single-source precursors to prepare a p-n-type BiOI-TiO photocatalyst. The heterojunction materials were carefully characterized by powder X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, etc. The synergistic effect of the two components of BiOI and TiO on the photocatalytic degradation of RhB in water is demonstrated. This is a very convenient method for obtaining a p-n-type BiOI-TiO heterojuction photocatalyst by just placing the ground TOC crystals into water.

2D Lead Iodide Perovskite with Mercaptan-Containing Amine and Its Exceptional Water Stability.

Two dimensional (2D) hybrid perovskites have attracted a great deal of interest because of their appropriate photovoltaic efficiency and environmental stability. Although some 2D hybrid perovskites with sulfur-containing amines have been reported, the cation having the mercaptan group has not been well explored yet. In this work, cysteamine (Cya, HS(CH2)2NH2), a mercaptan-containing amine, was introduced into 2D hybrid perovskite. Two 2D lead iodides with different structures, (HCya)2PbI4 (1) and (HCya)7Pb4I15 (2), were isolated as a red low-temperature phase and a yellow high-temperature phase, respectively. X-ray single-crystal structural analysis showed that the red phase 1 is a single layered corner-shared perovskite and that the yellow phase 2 is a corner/edge-shared quasi-2D perovskite. A thermo-induced reversible 1 to 2 phase transition was found in this synthetic system. The configuration of HCya cation greatly influences the crystallization equilibrium, generating different structures of the lead halides. The single-crystal structure of 1 is discussed in comparison with that of (HAE)2PbI4 (AE = HO(CH2)2NH2), an analogue of 1. The different effects of OH and SH groups on the 2D frameworks are studied based on their hydrogen bonding properties. More remarkably, although the two perovskites have similar structures, the (HCya)2PbI4 (1) has an intrinsic water stability that is much more stable than (HAE)2PbI4, which should be attributed to the affinity of the SH group with lead on the surface of the lead halide.

Tetrathiafulvalene-based double metal lead iodides: structures and electrical properties.

Introducing electronically active organic components into lower dimensional metal halide compounds is an effective strategy to improve the electronic properties of hybrid metal halide materials. We have previously used this strategy to explore hybrid halides with tetrathiafulvalenes (TTFs) and a series of lead iodides and bismuth halides were isolated. The electronic properties were improved notably using this modification. In this work, we expand the study of TTF based main-group metal halides to double metal halides with mixed lead and copper transition metals. Two hybrid TTF-lead-cuprous iodides, formulated as [TTF]5[Pb2Cu2I10]·H2O (1) and [TTF]2[PbCu2I6] (2), and two monometal analogues of [TTF]2[Cu4I6]·H2O (3) and [TTF]2[Ag4I6] (4) were crystallographically characterized. The anion of 1 is a 0D cluster, while that of the others is a 1D chain structure. The anion structures of 1-4 are novel and are reported for the first time. The TTF moieties are stacked to form a 2D framework in 1 and 1D columns in 2-4. We found that the semiconductor properties of the hybrids are related to electron donation from an anion to a cation. The electronic state of the TTF cations is another significant factor that affects the electronic properties of the materials. More notably, this work proved that the conductivity and photoconductivity of the mixed metal iodides are superior to those of the monometal iodides.

Effect and mechanism of picroside n on p38 mitogen activated protein kinase signal transduction pathway after cerebral ischemia/reperfusion in rats / 解剖学报

Objective To explore the neuroprotective effect and mechanism of picroside II on p38 mitogen activated protein kinase (p38 MAPK) signal transduction pathway after cerebral ischemia/reperfusion injury in rats. Methods A total of 150 healthy male Wistar rats were subject to establish middle cerebral artery occlusion/reperfusion (MCAO/R) models by inserting a monofilament thread. All rats were randomly divided into sham group, model group, picroside (Pier) group, anisomycin (Anis, agonist of p38 MAPK) group, Anis+Picr group, SB203580 (SB, inhibitor of p38 MAPK) group and SB+Picr group. The neurobehavioral function was evaluated by modified neurological severity score points (mNSS) test. The structure of neuron was observed using HE staining. The apoptotic cells were counted using TUNEL assay. The expression of phosphorylated p38 MAPK (p-p38 MAPK) in cortex was determined using the immunohistochemistry. And the expressions of p-p38 MAPK, phosphorylated MAPK activated protein kinase-2 (p-MK2), phosphorylated cytoplasm phospholipase A2 (p-cPLA2), interleukin-6 (IL-6) and tumor necrotic factor a (TNF-α) were determined by Western blotting. Results No neurological behavioral malfunction was found in sham group. In model group, the damage of neuron was worsened, while the neurobehavioral function score, apoptotic cell index and the expressions of p-p38 MAPK, p-MK2, p-cPLA2,IL-6 and TNF-α increased significantly than those in control group. No significant difference was found in TNF-α. In Pier group, SB group and SB+Picr group, the damage of neuron was lighter, the neurological behavioral function was improved, the number of apoptotic cells and the expressions of p-p38 MAPK, p- MK2, p-cPLA2 and IL-6 decreased significantly than those in model group. In Anis group and Anis + Pier group, the damage was worsen, the cerebral infarction was larger, and the expressions of p-p38 MAPK, p-MK2, p-cPLA2 and IL-6 increased significantly than those in control group. Conclusion Picroside II can protect the neuron from the apoptosis and inflammation reaction after MCAO/R by inhibiting p38 MAPK signal transduction pathway in rats.

Tetrathiafulvalene-Based Metal-Organic Framework as a High-Performance Anode for Lithium-Ion Batteries.

Metal-organic frameworks (MOFs) have aroused great interest as lithium-ion battery (LIB) electrode materials. In this work, we first report that a pristine three-dimensional tetrathiafulvalene derivatives (TTFs)-based zinc MOF, formulated [Zn2(py-TTF-py)2(BDC)2]·2DMF·H2O (1) (py-TTF-py = 2,6-bis(4'-pyridyl)tetrathiafulvalene and H2BDC = terephthalic acid), can work as a high-performance electrode material for rechargeable LIBs. The TTFs-Zn-MOF 1 electrode displayed a high discharge specific capacity of 1117.4 mA h g-1 at a current density of 200 mA g-1 after 150 cycles along with good reversibility. After undergoing elevated discharging/charging rates, the electrode showed superior lithium storage performance in the extreme case of 20 A g-1 and could finally recover the capability when the current rate was back to 200 mA g-1. Particularly, specific capacities of 884.2, 513.8, and 327.8 mA h g-1 were reached at high current densities of 5, 10, and 20 A g-1 after 180, 175, and 300 cycles along with good reversibility, respectively. Such an excellent performance is first reported for the LIB anode materials. TTFs-Zn-MOF 2, namely, [Zn2(py-TTF-py) (BDC)2]·DMF·2H2O (2), was prepared as a contrast to explore the relationship between the structures of the electrode materials and the electrochemical properties. Based on the structural analysis of 1 and 2 and ex situ X-ray photoelectron spectroscopy, the TTF moiety and the twofold TTF pillar play a key role in the excellent electrochemical performance. The full cell of MOF 1 with NMC 622 delivered the capacity of 131.9 mA h g-1 at 100 mA g-1 with the Coulombic efficiency of 99.45% after 70 cycles and exhibited the tolerance to high-current operation.

Hybrid Lead Iodide Perovskites with Mixed Cations of Thiourea and Methylamine, From One Dimension to Three Dimensions.

Hybrid halide perovskites featuring as new materials of high-performance solar cells have attracted great research interest. The temperature-dependent dimensional transition of halide perovskites is a crucial handle in the preparation of perovskite films. Only the small cations of methylammonium (MA) or formamidinium (FA) have been involved for most of the dimensional transition materials. In this work, thiourea (tu) is introduced into hybrid halide materials. A new series of 1D ribbonlike hybrid lead iodides with tu and MA cations are reported that were crystallographically characterized as MAn(Htu)n+1PbnI4n+1 (n = 1-4 denoted as 1-4, respectively; in 1, MA is replaced by tu). The width of the perovskite ribbon increases from one PbI6 octahedron to four corner-fused octahedra. Compounds 2 and 3 can be turned into a black 3D perovskite after annealing. This is an unusual mixed MA-tu hybrid halide perovskite system, in which the tu molecule plays an important role in manipulating the dimensions and their photoconductive properties. Scanning electron microscopy of the blackened sample shows that there are a lot of regular vent holes on the smooth crystal surface with sizes of hundreds of nanometers. The tunable structures and porous crystals might be advantageous in the sense of material modulation.

Cobalt Metal-Organic Frameworks Incorporating Redox-Active Tetrathiafulvalene Ligand: Structures and Effect of LLCT within the MOF on Photoelectrochemical Properties.

Understanding the effect of charge transfer on the physical properties of metal-organic frameworks (MOFs) is essential for designing multifunctional MOF materials. In this work, three redox-active tetrathiafulvalene (TTF)-based MOFs, formulated as [Co6L6(bpe)6(EtOH)2(MeOH)2(H2O)]n·5nH2O (1), [Co5(µ3-OH)2L4(bpe)2]n (2), and [CoL(bpa)(H2O)]n·2nH2O (3) (L = dimethylthio-tetrathiafulvalene-bicarboxylate, bpe = 1,2-bis(4-pyridyl)ethene, bpa = 1,2-bis(4-pyridyl)ethane), are crystallographically characterized. Complexes 1 and 3 are two-dimensional (2D) coordination polymers, and 2 features an unusual three-dimensional (3D) MOF. The structure of 2 contains a cluster chain constructed from µ2-O bridged pentanuclear cluster subunits, which is first found for 3D MOFs. Complexes 1 and 2 are comprised of the same ligands L and bpe but with different multidimensional configuration, and complexes 1 and 3 have the same 2D layered structures with the same ligand L but with different conjugation ligand bpe/bpa, which provide a good comparison for the structure-property relationship. The charge-transfer (CT) interactions within MOF 1 are stronger than those of 2 due to the closer packing of electron donor (D) L and electron acceptor (A) bpe in 1, and no CT occurs within MOF 3 because of the unconjugated bpa. The order of photocurrent density is 1 > 2 ≫ 3, which is in accordance with that of CT interactions. Further analysis reveals that the CT interactions within the MOF are not beneficial for the supercapacitance which is verified by the highest supercapacitance performance of 3. This work is the first study of the structures and CT effects on the supercapacitance performance.

Molybdenum-titanium oxo-cluster, an efficient electrochemical catalyst for the facile preparation of black titanium dioxide film.

Black-TiO2 has become increasingly interesting as a promising photoactive material. Most of the preparations for black-TiO2 involve either high temperature calcination, plasma, lengthy chemical reactions or dealing with dangerous or toxic chemicals. We found, by accident, that Mo-Ti oxo-clusters are efficient catalysts for the hydrogenation of a TiO2 electrode to black-TiO2 at room temperature. A series of Mo-Ti oxo-clusters, [Ti4Mo4O10(OR)14(X-BA)2] (BA = benzoate, X = H (1), F (2), Cl (3), and Br (4)), were prepared and were characterized by crystallography. They have a Mo4Ti4 structure with Mo(v)-Mo(v) metal-metal interactions. The activated hydrogen (H*) generated by electrochemically catalytic water splitting turns the TiO2 electrode to black-TiO2 at room temperature, due to the reduction of Ti(iv) to H+Ti(iii). The potentials applied for water reduction must generally be higher than the overpotential at the TiO2 electrode (-1.0 V vs. RHE). In this work, the onset potential of hydrogen evolution significantly decreased to -0.1 V vs. RHE. Using this blackened 1-TiO2 electrode, the effective electrochemical catalytic degradation of a dye was examined in comparison with the degradation using the white TiO2 electrode. This work provides a method for the facile preparation of a black-TiO2 film, and is a step forward in black-TiO2 research.

Eu-phen Bonded Titanium Oxo-Clusters, Precursors for a Facile Preparation of High Luminescent Materials and Films.

Incorporation of Eu complexes into various organic or inorganic matrixes is one of the acceptable strategies to obtain displaying materials having practical applications. In this work, we report a convenient approach to preparing high luminescent organic-inorganic hybrid materials and films from the europium-titanium oxo-clusters (EuTOCs) having photoactive antenna ligands. Three Eu2Ti4 oxo-clusters were synthesized and crystallographically characterized. They are the first reported lanthanide-TOCs coordinated with 1,10-phenanthroline (phen) and 2,2'-bipyridine (bpy) as photoactive ligands, Eu2Ti4O6(phen)2(pa)10 (1) (pa = propionate), Eu2Ti4O6(bpy)2(pa)10 (2), and Eu2Ti4O6(phen)2(MA)10 (3) (MA = methacrylate). Benefitting from the photoactive antenna ligands and the rigid cluster structures, these clusters showed bright red luminescence with quantum yield in the range of 60-80% and long lifetime up to 3.0 ms. Unlike those physically mixed polymeric materials, the MA coordinated compound 3 can be self-polymerized to form a brilliant luminescent film. The film coated slide was used to develop a fluorescence sensor for biomolecule ascorbic acid (AA). The low detection limit and reusable properties suggest great potential for such EuTOC films in real applications.

A Series of Tetrathiafulvalene Bismuth Chlorides: Effects of Oxidation States of Cations on Structures and Electric Properties.

Most large organic cations in the low-dimensional hybrid halide perovskites deteriorate the photoelectric conversion efficiency of the cells. Integrating electronically active organic components into hybrid metal halides is an effective method to improve their photoelectric properties. In this work, a series of compounds obtained by hybridizing redox-active tetrakis(methylthio)tetrathiafulvalene (TMT-TTF) with bismuth chloride, formulated as [TMT-TTF]4[Bi6Cl22] (1 and 1'), [TMT-TTF]3[Bi4Cl16] (2), [TMT-TTF]2[Bi3Cl13] (3), [TMT-TTF]2[Bi2Cl10] (4), and {[TMT-TTF][Bi2Cl8]}n (5), were crystallographically characterized. These hybrids exhibit changeable oxidation states of the TTF moiety. The radical cation TTF•+ exists in 1 and 1', while a mixed-valence TTF•+/TTF2+ appears in 2 that has never been documented in any compounds and the dication TTF2+ exists in 3-5 that has never been introduced into hybrid organic-inorganic materials. The different charged states of the TTF cations lead to various degrees of connectivity of metal chloride anions, which exert a significant effect on the cation-anion arrangement and result in different supramolecular interactions between TMT-TTF and between cations and anions. The changeable oxidation states of the TTF moiety and varying degrees of metal chloride connectivity provide a good comparison among these hybridized bismuth chlorides. The order of conductivity is 2 > 1 > 1' > 3 ≈ 4 ≫ 5, which results from the synergistic effect of different oxidation states, the packing of TMT-TTF cations, and back charge transfer from the Bi-Cl anion to the TMT-TTF cation. Notably, the electrical conductivity and carrier mobility can be modulated with the fact that compound 2 has the highest performances in the dark, while in light, these properties of 1 and 1' are in turn higher than that of 2. The order of the photocurrent densities is in accordance with the increase of carrier mobility under irradiation of light. This work is the first systematic study of hybrid metal halides with various oxidation states of TTFs and presents a clear structure-property relationship and offers a fresh view on the design of new perovskite materials at the molecular level.

A Potential Hybrid Hole-Transport Material Incorporating a Redox-Active Tetrathiafulvalene Derivative with CuSCN.

Inorganic CuSCN and organic tetrathiafulvalene derivatives (TTFs) have been exploited as hole-transport materials (HTM) in hybrid perovskite solar cells. To develop new HTM, we herein report two hybrid materials incorporating redox-active TTFs with CuSCN framework (TTFs-CuSCN). Single-crystal analysis showed that compound [Cu2(py-TTF-py)(SCN)2] (1) is three-dimensional (3D) and compound [Cu(py-TTF-py)(SCN)] (2) is two-dimensional (2D) (py-TTF-py = 2,6-bis(4'-pyridyl)tetrathiafulvalene). There are covalent coordination interactions between CuSCN and py-TTF-py and short S···S contacts between the py-TTF-py ligands for both compounds. Besides, C···S contacts exist between py-TTF-py ligands of the neighboring 2D networks in 2, which facilitate the charge transfer and supply efficient multidimensional pathways for carrier migration. As a result, 2 presented better semiconductor performance in comparison with that of 1. The performance of 2 related to the HTMs could be significantly improved by modulating the electronic state of the TTFs-CuSCN framework via oxidative doping. The iodine-doped 2D material (2-I2) gives the most excellent conductivity and carrier mobility, which might be a potential new HTM.