A novel transition-metal-linked hexaniobate cluster with photocatalytic H2 evolution activity

A novel transition-metal (TM) complex based on Lindqvist polyoxoniobate K₁₀[(Nb₆O₁₉)Cr^III(H₂O)₂]₂·28H₂O (1) has been synthesized by a new two-pot synthesis strategy and structurally characterized by single crystal X-ray diffraction analysis, IR spectrum, UV–vis spectroscopy, XRPD and TG analysis. Compound 1 crystallizes in the C2/m space group with a = 32.143(19) Å, b = 10.030(6) Å, c = 12.878(8) Å, β = 110.611(9)°, and V = 3886(4) ų. X-ray structure analysis reveals that polyanion [(Nb₆O₁₉)Cr^III(H₂O)₂]₂^10 − (1a) represents the first example of two nuclear dimeric polyoxoniobate, in which two Lindqvist anions [Nb₆O₁₉]⁸ are sandwiched by two {Cr^III(H₂O)₂} groups. Further, 1 exhibits photocatalytic H₂ evolution activity.     

Formation of extended 1D coordination polymers in tetrathioether complexes of mercury(II): Effect of the organic substituents on the crystal structures of {Si(CH2SR)4}HgBr2 (R = Me,Ph)

Two novel one-dimensional (1D) coordination polymers of stoichiometry [{Si(CH₂SR)₄}HgBr₂]_n (R = Me, 2a; R = Ph, 2b) have been prepared by treatment of HgBr₂ with the functionalized silanes Si(CH₂SR)₄ (R = Me, 1a; R = Ph, 1b) acting as tetradentate thioether ligands. The extended structures result from intermolecular Hg–S interactions linking the monomeric {Si(CH₂SR)₄}HgBr₂ units, as established for 2a, b using single-crystal X-ray diffraction. The effective coordination around the Hg atoms in both compounds is best described as distorted octahedral.     

Reversible water inclusion in a porous magnetic material synthesized from copper(II) incorporated metal-organic framework showing alternate ferro- and antiferromagnetic interactions

X-ray structural analysis shows that {[Cu₂(CTA) (H₂O)] · 5 H₂O}_n constitutes infinite one-dimensional parallel chains along the c-axis with water columns running down the crystallographic a-axis. The inclusion of water molecules is reversible and is confirmed by X-ray powder diffraction studies. The magnetic data (2–300 K) reveal that there are alternate ferro- (J = 0.29 cm⁻¹) and antiferromagnetic (J = −2.5 cm⁻¹) interactions.     

A luminescent 2,2′-bipyridyl tricarbonyl rhenium(I) complex containing a non-bridging dicyanamide ligand

fac-(bpy)Re(CO)₃CF₃SO₃ reacts with sodium dicyanamide in THF/MeOH/H₂O to give fac-(bpy)Re(CO)₃N(CN)₂ (1) in 81% yield. Complex 1 was characterized spectroscopically and electrochemically using NMR, IR, UV–Vis, fluorescence and cyclic voltammetry. Complex 1 crystallizes in the P2₁/c space group with a = 7.2004(3) Å, b = 12.9547(5) Å, c = 16.8523(6) Å, β = 101.989(1) °, and Z = 4. Photophysical measurements indicate the π-acceptor ability of N(CN)₂⁻ as equivalent to that of the 4-N,N-dimethylaminopyridine ligand. Strong luminescence is observed in solution at room temperature and in 4:1 ethanol:methanol matrices at 77 K attributed to the ³MLCT state.     

Comparison of HPLC and NMR characterization of the stereogenic properties of cyclotriphosphazene derivatives containing two equivalent centres of chirality: Cis (meso) and trans (racemic) isomers

The di-spiro derivatives of the reaction of gem-disubstituted cyclotriphosphazenes, N₃P₃Cl₄X₂ (X = Ph, PhS, PhNH, PhO) with 3-amino-1-propanol are expected to exist as cis and trans geometric isomers and exist as meso and racemic, respectively. The geometric isomers were separated by column chromatography on silica gel and analyzed by elemental analysis, mass spectrometry, and ³¹P and ¹H NMR spectroscopies. The stereogenic properties of all the compounds (trans, 2a–5a) and (cis, 2b–5b) were investigated by ³¹P NMR spectroscopy on the addition of a chiral solvating agent (CSA), (S)-(+)-2,2,2-trifluoro-1-(9′-anthryl)ethanol; one example of a derivative with the trans configuration (compound 5a, X = PhO) has been found where the ³¹P NMR/CSA method does not lead to the expected separation of the signals of enantiomers, even up to a molar ratio of CSA:compound of 50:1. On the other hand, chiral HPLC methods have been developed in order to characterize the trans (2a–5a) and cis (2b–5b) forms of the cyclotriphosphazene derivatives and give good separation of enantiomers for the trans disubstituted compounds (2a–5a). It is found that chiral HPLC is more reliable than the ³¹P NMR/CSA method for characterising the stereogenic properties of the cis and trans isomers of di-spiro 3-amino-1-propanoxy cyclophosphazene derivatives.     

LiBa1.5[B5O8(OH)3]: A new 1-D metal borate chain constructed from B5O9(OH)36 − cluster units

A new mixed metal borate LiBa_1.5[B₅O₈(OH)₃] (1) has been hydrothermally synthesized and structurally characterized by FT-IR spectroscopy, powder X-ray diffraction, single crystal X-ray diffraction, and thermogravimetric analysis, respectively. 1 crystallizes in the monoclinic system, space group C2/c, a = 11.2839(7) Å, b = 7.3974(4) Å, c = 20.7151(13) Å, β = 103.392(6)°, V = 1682.10(17) ų and Z = 8. The structure consists of infinite one-dimensional (1-D) borate chains constructed from B₅O₉(OH)₃^6 − cluster units. These BO chains are further linked by the Ba^2 + and Li⁺ cations to form a 3-D framework.     

Single crystal X-ray structure analysis for two thiazolylazo indole dyes

To determine the tautomeric form of the hetarylazo indole dye 3-(5-methylthiazol-2-yldiazenyl)-2-phenyl-1H-indole (1), 1-methyl-3-(thiazol-2-yldiazenyl)-2-phenyl-1H-indole (2) was synthesized as a model compound and both molecules were characterized by single crystal X-ray diffraction. (1) crystallized in the monoclinic system, space group C2/c, a = 31.064(2), b = 7.4051(5), c = 27.7138(18) Å, β = 97.617(1)°, V = 6318.9(7) Å³, Z = 8, while dye 2 crystallized in the monoclinic system, space group P2₁/n, a = 11.4660(11), b = 9.8223(9), c = 14.2049(14) Å, β = 97.418(2)°, V = 1586.4(3) Å³, Z = 4. The asymmetric unit of 1 contains two crystallographically independent molecules, in which geometries and conformations differ slightly, while there is only one molecule in the asymmetric unit for 2. The intermolecular N–H?N hydrogen bonds in (1) link the molecules, via parallel, infinite sheets, along the a axis and stabilize the crystal structure; in 2, there is no classical intermolecular hydrogen bond.     

Sandwich type organic-inorganic hybrid of 3d–4f heterometallic containing germanotungstates [{Cu2(1,10-phen)2(μ-CH3COO)2}Ln(α-GeW11O39)2]11 −: Syntheses,crystal structures,magnetic and photoluminescence properties

Alkali salts of organic-inorganic hybrid 3d-4f heterometallic containing derivatives of sandwich type germanotungstates: [{Cu₂(1,10-phen)₂(μ-CH₃COO)₂}Ln(α-GeW₁₁O₃₉)₂]^11 − [Ln = Pr^III (1a), Nd^III (2a), Sm^III (3a), Eu^III (4a), Gd^III (5a); 1,10-phen = 1.10-phenanthroline] have been prepared in the aqueous potassium acetate buffer (pH 4.7) solution. All these compounds were synthesized following by one pot reaction procedure under mild reaction conditions. All compounds were isolated as mixed alkali sodium/potassium salts from the solution and used for further structural characterization by single crystal XRD, powder-XRD, FT-IR, liquid UV/vis, solid state photoluminescence spectroscopy and thermo-gravimetric analysis. FT-IR spectra and powder-XRD pattern suggest that all compounds (1a–5a) are isomorphous. Further single crystal XRD analysis shows that all these compounds exhibit sandwich-type [Ln(α-GeW₁₁O₃₉)₂]^13 − structural feature in the polyoxoanions as the fundamental building block units, and the copper complexes coordinated with 1,10-phen and acetate ligands are coordinated to the terminal oxygen of the polyanion. The compounds 1a, 3a and 4a show good photoluminescence properties at room temperature. The compound 5a shows weak ferromagnetic behavior.     

β-Diketones derived from cyclopentadienyl rhenium tricarbonyl

The acetyl complex (η⁵–C₅H₄COCH₃)Re(CO)₃ reacts with KO^tBu and an excess of appropriate ester to provide cyrhetrenyl-β-diketones complexes (η⁵–C₅H₄COCH₂COR)Re(CO)₃ (R = CF₃, 1a; CH₃, 1b; Ph, 1c). These new 1,3-diketones exist predominantly as enol tautomer, although a enol/keto mixture of approx. 10:1 is present in complexes 1b–c, in chloroform-d solution. The complexes have been characterized by spectroscopic techniques IR, ¹H and ¹³C NMR and mass spectrometry. X-ray crystallography of complex 1b shows that only the enol form occurs in the solid state. The O–C–C–C–O fragment of the molecule is planar with asymmetric enolisation in the direction furthest from the cyrhetrenyl group.     

Cobalt(II) complex containing two-ring scorpionate-like ligands formed in situ. Studies on the [Co0–1-hydroxymethyl-3,5-dimethylpyrazole–MoO3–NH4I] system

We report preparation and characterization of a novel complex cis–mer [Co(L)₂]I₂ CH₃OH (1) (L-N,N-bis(1-(3,5-dimethylpyrazolylmethyl)amine)) isolated from the [Co⁰–1-hydroxymethyl-3,5-dimethylpyrazole–MoO₃–NH₄I] system. A two-ring scorpionate ligand (L) was obtained in situ via redox and condensation processes. The catalytical properties of MoO₃ are responsible for the formation of this atypical scorpionate ligand. Compound (1) crystallizes in the orthorhombic space group Pna2₁ with a = 24.5578(14) Å, b = 13.8388(8) Å, c = 9.6072(7) Å, V = 3265.0(4) Å³ and Z = 4. The metal ion coordinates through six nitrogen atoms which belong to two tridentate ligands forming a deformed octahedron. The complex was characterized by IR, FIR, UV–VIS and magnetic investigations. The ligand was ranked in the spectrochemical series between imidazole and bipyridine. The crystal field splitting of tridentate N-donor L was found to be smaller in comparison to e.g. bidentate bipyridine.     

Decomposition of allantoin in the presence of Cu(II) ions resulting in the formation of a coordination polymer containing oxalate species

A novel Cu(II) coordination polymer, [Cu(ox)(DMSO)₂]_n (1) (ox-oxalate dianion, DMSO-dimethyl sulphoxide) has been prepared in the reaction of copper nitrate dihydrate and allantoin (5-ureidohydantoin) in DMSO/water solution. Compound (1) crystallizes in the monoclinic, space group P121/c1 with a = 5.1785(7), b = 13.6311(18), c = 8.5386(12) Å, β = 107.524(12)°, V = 574,76(14) Å³, Z = 4, D_cal = 1779 mg/m³, R₁ = 0.0449. The metal ion coordinates through four oxygen atoms belonging to two bidentate bridging oxalate ligands, and two oxygen atoms from two DMSO ligands forming an elongated octahedron. The crystal structure was confirmed by FT-IR and Uv–vis spectroscopic data.     

Photo- and electroluminescence from deep-red- and near-infrared-phosphorescent tris-cyclometalated iridium(III) complexes bearing largely π-extended ligands

Deep-red- and near-infrared-phosphorescent tris-cyclometalated iridium(III) complexes bearing largely π-extended cyclometalated (C^N) ligands were newly synthesized, and their photo- and electroluminescence properties were investigated. When 2-(benzo[b]furan-2-yl)quinoline and 2-(benzo[b]thiophen-2-yl)quinoline were employed as C^N ligands, deep-red photoluminescence was obtained (Ir-1a and Ir-1b; λ_PL in CH₂Cl₂, 647 and 652 nm, respectively). In the case of the isoquinoline analogues of Ir-1a and Ir-1b, emission maxima were further red-shifted, ranging from deep-red to near-infrared regions (Ir-2a and Ir-2b; λ_PL in CH₂Cl₂, 696 and 690 nm, respectively). Especially, Ir-2b showed an excellent photoluminescence quantum yield (Φ_PL = 0.15), and a polymer light-emitting diode doped with Ir-2b exhibited deep-red–near-infrared electroluminescence with a high external quantum efficiency (λ_EL = 694 nm, η_{ext max} = 1.41%).     

Design and synthesis of two macrocyclic dinuclear coordination polymers with binding of nitric oxide

Two new coordination polymers of Robson-type macrocycles, {[CuL¹]_n (1) and {[CuL²]_n (2), were obtained by the condensation between bapa and N,N′-bis(3-formyl-5-R-salicylimine)-1,2-propylenediimine in the presence of Cu(II). These polymers have the common feature that the 3-methylaminopyridine group in one ligand coordinates to the metal ion in the neighboring coordination unit, leading to the formation of one-dimensional infinite chain. The formation of NO complexes has been confirmed by UV/Vis spectrophotometry. The binding constants were calculated to be 8.18 × 10² M^− 1, 1.2 × 10³ M^− 1 for 1 and 2, respectively. The control experiments revealed there was non-reversible binding of NO, which can be ascribed to specially coordination environment of the central Cu(II) ions. Moreover, the interactions of the complexes with calf thymus DNA (CT-DNA) have been measured by agarose gel electrophoresis, and the results showed that they can not cleavage the CT-DNA. These two complexes can be served as potential NO scavengers.Graphical abstractTwo new coordination polymers of Robson-type macrocycles, {[CuL¹]_n (1) and {[CuL²]_n (2), were obtained by the condensation between bapa and N,N′-bis(3-formyl-5-R-salicylimine)-1,2-propylenediimine in the presence of Cu(II). The NO absorption experiments revealed a moderate binding to NO and control experiments showed the non-reversibility of the binding NO to these two macrocyclic metal Cu(II) complexes.     

A novel paradodecatungstate-B compound decorated by transition metal copper,Na2Cu5(H2O)24(OH)2[H2W12O42]·10H2O: Synthesis,structure and antitumor activities

A new paradodecatungstate-B compound decorated by transition metal copper, Na₂Cu₅(H₂O)₂₄(OH)₂[H₂W₁₂O₄₂]·10H₂O (1), has been synthesized by convenient aqueous solution method and structurally characterized by single-crystal X-ray diffraction, IR spectrum, elemental analysis and TGA. The compound crystallizes in the triclinic P-1 space group with a = 10.7140(8) Å, b = 12.9476(9) Å, c = 13.6696(10) Å, α = 73.56°, β = 75.73°, γ = 67.69°, V = 1661.8(2) ų and Z = 1. In compound 1, polyanion of [H₂W₁₂O₄₂]^10 − acts as a dodecadentate ligand that links copper and sodium cations, forming a remarkable three-dimensional framework. The experiment of antitumor activities in vitro shows that the title compound exhibits remarkable inhibitory actions on human cervical carcinoma HeLa cells, ovarian carcinoma SKOV-3 cells, hepatoma HepG2 cells and neuroblastoma SHY5Y cells.     

Synthesis of 1,1′-ferrocene bis(carboxypyrazole) compounds and displacement of the pyrazole ligands

The reaction of 1,1′-ferrocenedicarbonyl chloride with pyrazole or 3,5-dimethyl pyrazole generates novel 1,1′-ferrocene bis(amide) compounds 1 and 2, respectively. The crystal structure of 1 shows that the pyrazole rings are essentially co-planar with each other and with the cyclopentadienyl rings. Attempts to use the complexes as a chelating ligand were unsuccessful. Instead, treatment of 1 or 2 with Mo(CO)₄(pip)₂, pip = piperidine, led to displacement of the pyrazole ligands and formation of the known amide compound, 1,1′-ferrocene bis carbonyl piperidine. Replacement of the pyrazole is ascribed to the weakness of the amide bond caused by the aromaticity of the pyrazole ring. Crystal data for C₁₈H₁₄FeN₄O₂ (1): monoclinic P2(1)/c, a = 13.3907(18) Å, b = 10.2112(14) Å, c = 11.3082(16) Å, β = 105.209(2)°, V = 1492.1(4) Å³, Z = 4.     

Coupling reaction of carbon dioxide and epoxides efficiently catalyzed by one-component aluminum–salen complex under solvent-free conditions

Four novel bifunctional aluminum–salen complexes (2a, 2b, 2c, and 2d) containing both Lewis acidic metal center and Lewis base quaternary phosphonium salt sites within one molecule and an aluminum–salen complex with a neutral tert-butyl group (2f) for comparison were synthesized and characterized by UV–vis, IR, ¹H, ¹³C, ²⁷Al NMR spectroscopy and Elemental analysis (EA). Their catalytic efficiencies as single-component catalysts toward the coupling reaction of carbon dioxide and propylene oxide were evaluated. These complexes exhibit catalytic activity in the order 2d > 2a > 2b > 2c ? 2f. ²⁷Al NMR spectra reveal the existence of five- and six-coordinated metal centers in the aluminum–salen complexes bearing a quaternary phosphonium salt group, whereas only five-coordinate aluminum species were found in the aluminum–salen complex with a neutral tert-butyl group. This indicates the importance of the six-coordinate aluminum center in enhancing the catalytic activity as well as an intramolecular cooperative effect in bifunctional aluminum–salen complexes 2a–d. The effects of reaction variables on the catalytic performance were investigated in detail. These new catalysts are highly stable to moisture and air and robust to impurities in the coupling reaction.     

Synthesis,reactivity, and X-ray structural characterization of a vanadium(III) oxidation pre-catalyst, (CpPOEtCo)VCl2(DMF)

Vanadium complexes are extensively used in the chemical industry as oxidation catalysts. During the course of our investigations into vanadium oxidation catalysis, the rich reactivity of a vanadium(III) scorpionate analogue complex, (CpP^OEtCo)VCl₂(DMF) (1), was investigated. The octahedrally coordinated 1 was prepared by mixing vanadium(III) chloride with Na(CpP^OEtCo) in DMF. The crystal structure of 1 has been determined through X-ray diffraction. Complex 1, C₂₀H₄₂Cl₂CoNO₁₀P₃V, crystallizes in the monoclinic space group P2₁/c with a = 38.566(9) Å, b = 9.499(2) Å, c = 18.149(4) Å, and β = 100.485(4)° with Z = 8. Complex 1 was found to be an effective pre-catalyst for the oxidation of 3,5-di-tert-butylcatechol to 3,5-di-tert-butylquinone. The reactivity studies, oxidative catalytic ability, as well as X-ray structural characterization of (CpP^OEtCo)VCl₂(DMF) will be discussed. ((CpP^OEtCo) = [η⁵-cyclopentadienyltris(diethylphosphito-κ¹P) cobaltate(III)⁻; DMF = N,N-dimethylformamide).     

A novel dimeric polyanion based on mono-manganese substituted Keggin-type phosphotungstate: (MnPW11O39)210 −

The novel dimeric polyoxometalate, (MnPW₁₁O₃₉)₂^10 − (1a), has been synthesized by reacting [B-α-PW₉O₃₄]^9 − with Mn^2 + ions in weak acid aqueous solution (pH = 5.3) under hydrothermal condition and isolated in the form of (C₁₄H₁₄N₄)₅H₁₀(MnPW₁₁O₃₉)₂·2H₂O (1), which was characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, and magnetic measurements. The polyanion represents the first example of dimeric polyanion based on mono-transition metal (TM) substituted Keggin-type polyanions linked by two TM-μ₂-O-TM bridges. Magnetic measurements show that the Mn┄Mn exchange interactions are weakly antiferromagnetic (J = ⁻ 0.53 cm^− 1).     

Synthesis and cytotoxicity of a ruthenium nitrosyl nitric oxide donor with isonicotinic acid and a cell penetrating peptide

The syntheses and properties of trans-[Ru(NH₃)₄(L)(NO)](BF₄)₃ (L = isonicotinic acid (inaH) (I) or ina-Tat48–60 (II)) are described. Tat48–60, a cell penetrating peptide fragment of the Tat regulatory protein of the HIV virus, was linked to the ruthenium nitrosyl through inaH. I and II release NO after reduction forming trans-[Ru(NH₃)₄(L)(H₂O)]^3 +. The IC₅₀ values against B16-F10 melanoma cells of I and II (21 μmol L^− 1 and 23 μmol L^− 1, respectively) are close to that of the commercially available cisplatin (33 μmol L^− 1) and smaller than similar complexes. The cytotoxicity is assigned to the NO released from I and II.     

Synthesis and mechanical properties of a new 1D hybrid organic-inorganic lead iodide

A new one-dimensional (1D) hybrid organic-inorganic lead iodide, [(Me)₂-bipy][Pb₂I₆] ([(Me)₂-bipy]^2 + = (C₆H₇N)₂^2 +) (1), has been synthesised and structurally characterised. Compound 1 crystalizes in an orthorhombic system with space group Pbca and cell parameters a = 17.6366(8), b = 16.0405(5) and c = 18.4693(7) Å, V = 5225.2(3) ų. In the structure, the 1D lead iodide columns are interspersed by the organic species to form a dense packed structure. Nanoindentation studies reveal orientationally dependent elastic moduli (8.6–10.5 GPa) and hardnesses (0.37–0.44 GPa), which can be rationalized with the underlying structure from an atomic level.