Synthesis, characterization and crystal structure of a novel 2D network structure based on hexacopper(II) substituted tungstoantimonate

The dimeric, hexacopper(II) substituted tungstoantimonate NaK₆[Cu₆Cl(SbW₉O₃₃)₂] · 14H₂O (1a) has been synthesized in good yield using a one-pot procedure by reaction of Cu²⁺ ions with the trilacunary precursor salt Na₉[α-B-SbW₉O₃₃] and characterized by IR spectroscopy, UV electronic spectroscopy, cyclic voltammetry and single-crystal X-ray diffraction. The title polyanion represents the first tungstoantimonate substituted by six copper centers and the polyanion as basic building unit is assembled into a two-dimensional network-like complex by Cu-OW bonds. The electrochemical behavior of 1a was investigated in buffer solution (pH 3.0) by cyclic voltammetry. In the potential range between −0.7 and 0.6 V, the compound exhibits the successive redox processes of the addenda atoms (W) followed by the redox reaction originating from the substituted Cu^II, which revealed the stepwise reduction of Cu²⁺ centers within the polyanion 1 before deposition of Cu⁰ on the glassy carbon electrode surface. The compound 1a is shown to have electrocatalytic properties towards the reductions of nitrate and nitrite.     

A series of POM-based hybrid materials with different copper/aminotriazole motifs

By controlling the reaction temperature, pH value of the system and the polyanion templates, three inorganic-organic hybrid materials based on Keggin polyoxometalate building blocks combined with Cu^I/II and 4-amino-1,2,4-triazole (4atrz) have been obtained by hydrothermal methods, namely, [Cu₃(μ₃-OH)(4atrz)₆][SiW₁₂O₄₀]·I·3H₂O (1), [Cu₄(4atrz)₆][SiW₁₂O₄₀] (2) and [Cu₆(4atrz)₆][PMo₁₂O₄₀]₂·H₂O (3). Crystal structure analysis reveals that the Cu^I/II/4atrz complexes in the three materials show tri-, tetra- and hexanuclear models, respectively. In compound 2, the copper clusters link the polyoxometalates into the chains by weak Cu-O bonds; while in the compounds 1 and 3, the copper clusters and the polyoxometalates stack by the ionic interactions. These compounds are further characterized by powder XRD, elemental analyses, FT-IR and thermogravimetric (TG) analyses. The electrochemical behavior of 3-CPE has been studied in the 1 M H₂SO₄ solution. The results exhibit that there are four pairs of redox waves attributable to the four consecutive two-electron processes of Mo(VI/V) couples and the redox process is surface-controlled.     

Synthesis and characterization of cellulose/silica hybrid materials with chemical crosslinking

The cellulose/silica hybrid biomaterials are prepared by sol–gel covalent crosslinking process. The tetraethoxysilane (TEOS) as precursor, γ-aminopropyltriethoxylsilane (APTES) as couple agent, and 2,4,6-tri[(2-epihydrin-3-bimethyl-ammonium)propyl]-1,3,5-triazine chloride (Tri-EBAC) as crosslinking agent, are used in the sol–gel crosslinking process. The chemical and morphological structures of cellulose/silica covalent crosslinking hybrids are investigated with micro-FT-IR spectra, nitrogen element analysis, X-ray diffraction, SEM, AFM, and DSC. The results show that the cellulose/silica hybrids form new macromolecular structures. In sol–gel process, inorganic particles are dispersed at the nanometer scale in the cellulose host matrix, bounding to the cellulose through covalent bonds. The cellulose/silica covalent crosslinking hybrid can form good and smooth film on the cellulose. The thermal properties of organic/inorganic hybrids are improved.     

Four novel polytungstate compounds built up of paradodecatungstate clusters and transition-metal complexes/transition metal: Synthesis, structure, and electrochemical properties

A series of novel polytungstates, [{Cu(bim)(H₂O)₂}₄(H₄W₁₂O₄₂)]·14H₂O 1, (Himi)₆[{Mn(imi)(H₂O)}(H₄W₁₂O₄₂)]·2H₂O 2, [{Cu_0.5(H₂O)}₂{Cu_0.5(H₂O)₂}₂{Cu (bim)(H₂O)₂}₂(H₄W₁₂O₄₂)]·10H₂O 3 and [{Na(H₂O)₄}₂{Cu_0.5(H₂O)}₄{Cu_0.5 (H₂O)_1.5}₂(H₄W₁₂O₄₂)]·3H₂O 4 (imi = imidazole; bim = 2,2′-biimidazole), have been obtained by the routine synthetic reactions in aqueous solution and characterized by IR, X-ray powder diffraction, UV, elemental analysis, TG and X-ray single-crystal diffraction. All the compounds contain the [H₄W₁₂O₄₂]⁸⁻ polyanions as building units. Compound 1 is isolated structure, which is modified with four {Cu(bim)(H₂O)₂}²⁺ fragments. The compound 2 exhibits an infinite 1D “wave-like” chain based on the interaction between the [H₄W₁₂O₄₂]⁸⁻ polyanion and [Mn(imi)(H₂O)]²⁺ complex. The 2D layered structure of the compound 3 is formed by the interconnection 1D [{Cu_0.5(H₂O)}₂(H₄W₁₂O₄₂)]⁶⁻ and [{Cu_0.5(H₂O)₂}₂(H₄W₁₂O₄₂)]⁶⁻ chains. While compound 4 can be abstracted of structural topology with (6,2)-connected 3D network. In addition, the electrochemical properties of these compounds are investigated.     

Synthesis and characterization of two new metal-organic materials based on In/btec

Two new metal-organic materials, In(2,2′-bipy)(btec)_0.5Cl (1) and In₂(phen)₄(Hbtec)₂ (2) (btec = 1,2,4,5-benzenetetracarboxylate, 2,2′-bipy = 2,2′-bipyridyl, phen = 1,10-phenanthroline) have been synthesized under mild hydrothermal condition. Their structures were determined by single-crystal X-ray diffraction and further characterized by X-ray powder diffraction, thermogravimetric analysis, IR, fluorescence spectroscopy, inductively coupled plasma (ICP) and elemental analysis. The structural analysis reveals that compound 1 exhibits a novel wavelike 2D layer with unusual contorted rhombic grids, while compound 2 possesses dinuclear In₂(phen)₄(Hbtec)₂ complex molecules. It is noteworthy that their structures finally extend to the higher dimensional supramolecular framework structures through the π-π stacking interactions of N-donor ligands. Additionally, these two compounds show strong fluorescence in the solid state at room temperature.     

Synthesis, characterization and structure of some arylantimony ferrocenylacrylates

A series of arylantimony ferrocenylacrylates with the formula (C₅H₅FeC₅H₄CHCHCO₂)_nSbAr_(5−n) (n=1, 2; Ar C₆H₅, 4-CH₃C₆H₄, 3-CH₃C₆H₄, 2-CH₃C₆H₄, 4-FC₆H₄) have been synthesized and characterized by elemental analysis, IR, ¹H NMR and mass spectra. The crystal structures of C₅H₅FeC₅H₄CHCHCO₂Sb(C₆H₅)₄ (I₁) and (C₅H₅FeC₅H₄CHCHCO₂)₂Sb(C₆H₅)₃ (II₁) have been determined by X-ray diffraction.     

Synthesis, characterization and structure of metallocene dicyanamide complexes

The bis(cyclopentadienyl) complexes [Cp₂Ti(dca)]₂O and Cp₂V(dca)₂ (dca = dicyanamide) have been prepared by reaction of sodium dicyanamide with aqueous solution of titanocene dichloride and vanadocene dichloride, respectively. The X-ray structure analyses of both complexes confirmed monodentate coordination of dicyanamide ligand through the terminal nitrogen atom of cyano group.     

Synthesis and characterization of new polyamino-cyclodextrin materials

With the aim of the synthesis of chemically modified cyclodextrins bearing polyamine pendant groups, potentially useful as capping agents for the preparation of nanosized metal systems or as auxiliaries for gene transfection, the reaction between the heptakis-(6-iodo)-(6-deoxy)-β-cyclodextrin and various polyamines has been explored. This synthetic approach allows obtaining materials constituted by mixtures of cyclodextrins, having different degrees of substitution, which were satisfactorily characterized by means of various complementary techniques (ESI-MS, NMR, potentiometric titration). The products obtained were successfully subjected to preliminary tests for their binding abilities towards suitable organic guests and as capping agents for the preparation of stable silver nanoparticles.     

Synthesis, characterization, spectroscopy, electronic and redox properties of a new nickel dithiolene system

A new dithiolene ligand with 3,5-dibromo substituted phenyl groups was designed and synthesized. The protected form of the ligand was reacted with a nickel salt providing neutral Ni(S₂C₂(3,5-C₆H₃Br₂)₂)₂ and anionic [Ni(S₂C₂(3,5-C₆H₃Br₂)₂)₂]⁻ isolated as a Bu₄N⁺ salt. Both were characterized by UV-Vis and IR spectroscopy and compared with the similar known molecular systems. They exhibit intense low energy transitions that are characteristic of such systems. The electrochemical behavior of these molecules was investigated by cyclic voltammetry.     

Synthesis, crystal structure, and properties of two sandwich-type tungstovanadates

Two dimeric tungstovanadates of the form [M₄(H₂O)₂(VW₉O₃₄)₂]¹⁰⁻ (M = Mn^II, Co^II) were synthesized and characterized by elemental analysis, thermogravimetric analysis and infrared spectroscopy. X-ray single crystal analysis revealed that the two polyanion clusters with isomorphic structure consist of two lacunary [VW₉O₃₄]⁹⁻ Keggin moieties linked by four Mn^II or Co^II ions, forming a sandwich-type structure. The temperature-dependent magnetic susceptibility measurements showed a dominant antiferromagnetic interaction in complex 1, while ferromagnetic interactions were found in complex 2. The electrochemical behaviors of complexes 1 and 2 were investigated in buffer solution at pH 4.8. Surface photovoltage spectroscopy (SPS) and electric field-induced SPS (EFISPS) revealed that complex 1 bears the behavior of an n-type semiconductor, while complex 2 shows no obvious signal.     

Synthesis and structure of new phosphine-substituted homo- and hetero-bimetallic carbonyl clusters of iron, ruthenium and nickel. Characterization of two inorganic-organometallic hybrid materials based on mesoporous SBA-15 silica

The reactions of the complexes Fe₃(CO)₁₂, H₂FeRu₃(CO)₁₃, H₂Ru₄(CO)₁₃ and CpNiRu₃(H)₃(CO)₉ with 2(diphenylphosphino)ethyl-triethoxysilane give considerable yields of the complexes Fe₃(CO)₁₀L₂ (1), H₂FeRu₃(CO)₁₀L₂ (2), Ru₄(CO)₁₀L₃ (3) and CpNiRu₃(H)₃(CO)₇L₂ (4) where L = Ph₂PCH₂CH₂Si(OEt)₃. The complexes (1-3) have been characterized by analytical and spectroscopic techniques. The structure of (4) has been determined by X-ray analysis. The presence of a phosphine containing the -Si(OEt)₃ group has been exploited for grafting complexes (3) and (4) on the mesoporous SBA-15 and the resulting inorganic-organometallic materials have been characterized by means of ICP-MS, FT-IR, DR-UV-vis spectroscopy, XRD and textural analysis.     

Synthesis, crystal structure and characterization of alkali metal hydroxoantimonates

Several alkali metal hydroxoantimonates, K₂[Sb(O)(OH)₅], Na[Sb(OH)₆], Cs[Sb(OH)₆] and Cs₂[Sb₂(μ-O)₂(OH)₈] were isolated from aqueous solutions and characterized by single crystal and powder X-ray diffraction studies and by FTIR and thermal analysis. Crystal structures involving [Sb(O)(OH)₅]²⁻ were never anticipated before, and this is also the first disclosure of a dinuclear antimonate [Sb₂(μ-O)₂(OH)₈]²⁻. Aqueous antimonate solutions of different pH were studied by high resolution electrospray mass spectrometry showing pH indifferent spectra and predominance of the mono and dinuclear antimonate species at pH 4-10.     

Preparation and characterization of mixed ammonium salts of Keggin phosphomolybdate

Keggin-type modified ammonium salts of molybdophosporic acid were prepared by partial substituting of the ammonium ions by X (X = Sb^III, Bi^III or Sn^II) ions. They were characterised by BET method, XRD, ³¹P NMR, UV-Vis, Raman, IR spectroscopies and thermal analysis (TG and DTA). It appeared that introducing an element X = Sb or Sn led to partially reduced compound corresponding to the electron exchange occurring between Sb(III) or Sn(II) and Mo(VI) without modification of Keggin structure.     

Synthesis, structure and characterization of two Pb(II) phosphonates with layered or 3D structures

Hydrothermal reactions of lead(II) acetate and N-cyclohexylimino-bis(methylenephosphonic acid) (C₆H₁₁N(CH₂PO₃H₂)₂, H₄L¹) or N,N′-bis(phosphonomethyl)-6-aminocaproic acid (HO₂C(CH₂)₅N(CH₂PO₃H₂)₂, H₅L²), respectively, resulted in two different new lead diphosphonates, namely, Pb₂L¹ · H₂O (1) and Pb₂[HL²] (2). Their crystal structures have been determined by single crystal X-ray diffraction. The structure of compound 1 contains a 〈0 0 1〉 lead(II) diphosphonate hybrid layer formed by Pb(II) ions interconnected by L¹ anions. Such layers are further interlinked by van der Waals force into a supramolecular structure. In compound 2, the Pb(II) ions are interconnected by the -N(CH₂PO₃H)(CH₂PO₃) and -CO₂ groups of the HL² anions forming an organic-inorganic hybrid layer. These layers are further interlinked by the -(CH₂)₅ groups of the HL² anions into a 3D structure.     

Synthesis of 2-morpholinetetraphenylporphyrins and their photodynamic activities

A series of 2-morpholinetetraphenylporphyrins functionalized with various substituents (Cl, Me, MeO group) at 4-phenyl position were prepared via nucleophilic substitution of 2-nitroporphyrin copper derivatives with morpholine by refluxing under a nitrogen atmosphere and then demetalization. Their basic photophysical properties, intracellular localization, cytotoxicities in vitro and in vivo were also investigated. All synthesized photosensitizers exhibited longer maxima absorption wavelengths than Hematoporphyrin monomethyl ether (HMME). They showed low dark cytotoxicity compared with that of HMME and were more phototoxic than HMME against Eca-109 cells in vitro. M3 also exhibited better photodynamic antitumor efficacy on BALB/c nude mice at a lower concentration. Therefore, M3 is a promising antitumor photosensitizer in photodynamic therapy application.     

Undecatungstophospho(aqua)ruthenate(II): One pot synthesis, characterization and non-solvent liquid phase aerobic oxidation of alkenes

Keggin type undecatungstophospho(aqua)ruthenate(II) was synthesized by the reaction of [PM₁₂O₄₀]³⁻ (aq) and RuCl₃ (aq) under mild conditions and characterized by various physicochemical techniques. The catalytic activity of the synthesized complex was evaluated for non-solvent liquid phase oxidation of styrene, cyclohexene and cis-cyclooctene using molecular oxygen. The synthesized complex acts as an efficient catalyst, especially for oxidation of cyclohexene. It shows very high activity for oxidation of cyclohexene in terms of conversion as well as selectivity. It gives 69% conversion with 100% selectivity for cyclohexane oxide.     

Synthesis, characterization, structure, molecular modeling studies and biological activity of sterically crowded Pt(II) complexes containing bis(imidazole) ligands

The syntheses, structures and biological evaluation of a series of cisplatin-like complexes containing bis(imidazole) derivatives - the so-called Joseph ligands - are described. Their cytotoxicity is discussed in terms of their polar surface area, rate of aquation, and lipophilicity. The X-ray crystal structure of the platinum diiodido derivative of dimethyl 2-(di(1H-imidazol-2-yl)methyl)malonate) is reported and compared to those of related systems. Molecular modeling studies are focused on the hydrogen bonding properties of such systems, and their relevance to antitumor activity.     

A series of inorganic-organic hybrid compounds constructed from bis(undecatungstophosphate) lanthanates and copper-organic units

A series of inorganic-organic hybrid compounds built from bis(undecatungstophosphate) lanthanates and copper-complexes, namely, H₈[Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][La(PW₁₁O₃₉)₂]}₂·18H₂O (1), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Ce(PW₁₁O₃₉)₂]}₂·16H₂O (2), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Pr(PW₁₁O₃₉)₂]}₂·18H₂O (3), H₆[Na₂(en)₂(H₂O)₄][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Nd(PW₁₁O₃₉)₂]}₂·14H₂O (4), H₆[Na₂(en)₂(H₂O)₅][Cu(en)₂H₂O]₄[Cu(en)₂]{[Cu(en)₂][Sm(PW₁₁O₃₉)₂]}₂·20H₂O (5), and H₇[Cu(en)₂]₂[Sm(PW₁₁O₃₉)₂]·10H₂O (6) (where en = 1,2-ethylenediamine), have been prepared. In these compounds, two lacunary [PW₁₁O₃₉]⁷⁻ anions sandwich an eight-coordinated Ln(III) cation to yield [Ln(PW₁₁O₃₉)₂]¹¹⁻ anion in a twisted square anti-prismatic geometry, which is further bridged by [Cu(en)₂]²⁺ fragments to generate a 1D zigzag-like chain. In 1-6, the coordination bond interactions and weak interactions between adjacent 1D chains play an important role in the zigzagging distances and angles of different 1D chains. The magnetic studies indicate that antiferromagnetic interactions exist in compounds 1, 2 and 4.     

Synthesis and characterization of guar gum templated hybrid nano silica

The objective of the present study was the fabrication of green adsorbent hybrids for which native guar gum was used as template to polymerize tetraethoxysilane. The properties and performances of the hybrids could be tailored by using varying molecular sizes of the partially depolymerized guar gum templates of various molecular sizes as control. Zn(II) uptake from aqueous solution was used as a criterion for evaluating the adsorbent efficiency. The optimum material (H4) in terms of maximum Zn(II) uptake, was obtained when the template size used was 375 kDa at a calcination temperature of 700 °C. H4 was also evaluated for Ca(II), Mg(II), Cd(II) and Hg(II) adsorption. To explore the other applicability areas, the hybrids have been extensively characterized using FTIR, XRD, TGA-DTA, PL, SEM, TEM and BET analyses. H4 was found to be as efficient as previously reported vinyl modified-silica nanohybrids. It had a high surface area (264 m²/g) with silica nanoparticles in the size range of 90-140 nm. Being thermally very stable and photoluminescent, the material can be potentially used for many biological, medical and environmental applications.