Optimisation of SFE method on-line coupled to FT-IR spectroscopy for the real-time monitoring of the extraction of tagitinin C in T. diversifolia

The monitoring in real time of dynamic extractions of tagitinin C from Tithonia diversifolia leaves was carried out with a home made high-pressure fiber optic cell which coupled a supercritical fluid extractor with carbon dioxide as the extraction medium and a FT-IR spectrometer equipped with a mercury cadmium telluride detector (MCT). The shape of extraction curves obtained during the monitoring was used to decide when to stop the supercritical fluid extraction (SFE).No significant density dependence of the molar absorption coefficient or wavenumber of the CO stretching vibration (ν_CO) of tagitinin C at 1668 cm⁻¹ was noticed.The physical characteristics of SCCO₂ governing the extraction yield of the active component from leaves were optimized by means of a central composite design (CCD). The studied variables were temperature (40, 60 and 80 °C) and pressure (8.0, 14.0 and 20.0 MPa) of the supercritical fluid.The composition profile of T. diversifolia extracts obtained by SFE was investigated in the range from 3400 to 2600 cm⁻¹ according to the pressure and temperature conditions of SCCO₂. The qualitative approach of the extracts composition was accomplished through the CH stretching vibrations (ν_CH) of components.     

Diplatinum(III) [Cl2(μ2-amidinate)4] compound derived from air oxidation of mononuclear cis-[Pt(NH3)2(amidine-κ)2] complex

The dinuclear platinum(III) complex [Pt₂Cl₂{μ₂-N(H)C(Et)N(H)}₄] (2) has been prepared by heating cis-[Pt(NH₃)₂{NHC(NH₂)Et}₂](Cl)₂ (cis-1) under aeration conditions in an EtOH/H₂O mixture at 70 °C for 2 d and it was characterized by elemental analyses (C, H, N), ESI⁺-MS, IR, ¹H and ¹³C NMR spectroscopies and also by X-ray diffraction. Complex 2 represents the second Pt^III dimer stabilized by the amidinate ligand ever known and it has a lantern-type structure with four amidinate ligands bridging two Pt^III centers with Pt–Pt distance of 2.4809(2) Å.     

Two 3D Coordination Polymers with New Topology Based on Mixed Ligands: Synthesis,Structure, and Photoluminescence Properties

Employing tetracarboxylate and imidazole mixed ligands to react with different transition meat salts afford two new 3D coordination polymers, {[Zn₂(BPTC)(BBI)₂]·(H₂O)₃·DMSO}_n (1) and {[Cd₂(BPTC)(BBI)₂]·H₂O}_n (2) (H₄BPTC?=?biphenyl-3,3′,4,4′-tetracarboxylic acid, BBI?=?1,1′-(1,4-butanediyl)bis(imidazole)). Both these two coordination polymers are 4-connected network topologies. Compound 1 features a unprecedented 3-nodal (4,4,4)-connected network topology with the point symbol {6⁴·8²}, and 2 displays a (4,4)-connected binodal network bearing new topology with the point symbol of {7²·8⁴}2{7³·8³}. Additionally, thermal stability and photoluminescence properties of 1 and 2 were investigated.     

Determination of the interaction within polyester-based solid polymer electrolyte using FTIR spectroscopy

Characterization and interaction behavior between Li⁺ ion and CO groups of a series polyester electrolyte have been thoroughly examined using Fourier transform infrared (FTIR). The “free/Li⁺ bonded” CO absorptivity coefficient of the LiClO₄/polyester can be determined quantitatively using FTIR spectrum ranging from 1800 to 1650 cm⁻¹ at 80 °C. Results from curve fitting show that the “free/Li⁺ bonded” CO absorptivity coefficient is 0.144 ± 0.005. The CO group of polymer electrolyte shows strong interaction with Li⁺ ion and a limit value of 95% “Li⁺ bonded” CO is approached in the polymer electrolyte system when the Li⁺ ion equivalent fraction is about 0.28. The molecular structure of polyester electrolyte does not affect significantly the efficiency of interaction between Li⁺ ion and CO.     

Analysis of the interaction using FTIR within the components of OREC composite GPE based on the synthesized copolymer matrix of P(MMA-MAh)

Poly(methyl methacrylate-maleic anhydride) (P(MMA-MAh)) has been synthesized from methyl methacrylate (MMA) and maleic anhydride (MAh) monomers. The molar ratio of monomers was found to be 1MAh:8MMA. The molecular weight of copolymer was determined in the order 10⁴ (g/mol).Rectorite modified with dodecyl benzyl dimethyl ammonium chloride (OREC) was used as a filler additive to modify gel polymer electrolytes (GPEs) which consisted of P(MMA-MAh) used as polymer matrix, propylene carbonate (PC) as a plasticizer and LiClO₄ as lithium ion producer. Characterization of interaction of CO in PC and copolymer with Li⁺ and OH group on OREC surface has been thoroughly examined using FTIR. The quantitative analysis of FTIR shows that the absorptivity coefficient a of copolymer/LiClO₄, PC/LiClO₄, PC/OREC and copolymer/OREC is 0.756, 0.113, 0.430 and 0.602, respectively, which means that the Li⁺ or OH bonded CO is more sensitive than free CO in FTIR spectra. The limit value of bonded CO equivalent fraction of copolymer/LiClO₄, PC/LiClO₄, PC/OREC and copolymer/OREC is 55, 94, 57 and 26%, respectively, which implies that all the interaction within the components is reversible and the intensity of interaction is ordered as PC/LiClO₄, PC/OREC, copolymer/OREC and copolymer/LiClO₄.     

Syntheses, characterization and biological activity of diorganotin(IV) derivatives of 2-amino-6-hydroxypurine (guanine)

Novel organotin(IV) derivatives of guanine of the general formula, R₂Sn(HGu)₂ (where, R = Me (1), n-Bu (2) and Ph (3)) have been synthesized by the reaction of R₂SnCl₂ with sodium salt of guanine (H₂Gu or 2-amino-6-hydroxypurine). The IR spectral studies suggest that guanine acts as a monobasic ligand coordinating through N(9) after its deprotonation. The weak bonding through C(6)O may also be evidenced, whereas ¹¹⁹Sn Mössbauer data suggest that the coordination number of tin is superior than four. The polyhedron around tin in R₂Sn(HGu)₂ is distorted trigonal–bipyramidal or pseudo-tetrahedral involving very weak interaction from CO group of neighboring molecule leading to polymerized structure. All the compounds exhibited potent anti-inflammatory activity with no appreciable side effects on blood pressure as evidenced by their very mild cardiovascular activity.     

Modification of electrodes with nanostructured functionalized thiadiazole polymer film and its application to the determination of ascorbic acid

We report the electropolymerization of 2-amino-1,3,4-thiadiazole (ATD) on glassy carbon (GC) and indium tin oxide (ITO) electrodes in 0.10 M H₂SO₄. The electropolymerized ATD (p-ATD) film was characterized by cyclic voltammetry, attenuated total reflectance (ATR)-FT-IR spectroscopy, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). The AFM image showed that the p-ATD formed a spherical-like structure with a thickness of 25 nm. XPS of the p-ATD film showed binding energies at 398.7, 400.3 and 401.3 eV in the N 1s region corresponding to –N, –NH– and –N⁺H–, respectively, and at 285.5 and 287.0 eV in the C 1s region corresponding to C–N and CN, respectively. The appearance of binding energies at 285.5 and 287.0 eV confirmed that the p-ATD film proceeded via C–N and CN linkages and not via C–C or CC linkages. The p-ATD film deposited on the GC electrode was successfully used for the determination of ascorbic acid (AA) at physiological pH. The amperometric current was increased linearly from 7.5 × 10⁻⁸ to 2.0 × 10⁻⁵, and the detection limit was found to be 0.28 nM (S/N = 3).     

Characterization of Cobalt(II) Phthalocyanine Catalyst Incorporated into Poly(aminosiloxane) Matrices

Cobalt phthalocyanine (CoPc) has been incorporated into various polysiloxane matrices by adding CoPc to appropriate mixtures of tri- and tetra-alkoxysilanes during hydrolytic condensation. The matrices contained Si(CH₂)₃NH₂ groups with alkyl or phenyl spacer groups between them. The cobalt content, the surface area and the pore volume all decrease as the spacer groups become larger. EPR and UV-visible spectroscopic data show that the CoPc is bound to the amine groups and that some are in the oxygenated form, (–NH₂)CoPc–O₂.     

Synthesis and spectroscopic analysis of cellulose sulfates with regulable total degrees of substitution and sulfation patterns via C NMR and FT Raman spectroscopy

Synthesis and spectroscopic characterisation of cellulose sulfate (CS) were reported. Various CS exhibiting diverse degrees of sulfation (DS_S) were prepared through acetosulfation or direct sulfation of cellulose. During the acetosulfation, intermediate product - cellulose acetate sulfate (CAS) - was formed after the comparative esterification and subsequent deacetylation of CAS led to CS. The direct sulfation proceeded quasi-homogeneously and heterogeneously in N,N-dimethylformamide (DMF) or homogeneously in N,N-dimethylacetamide (DMAc)/LiCl mixture. The total DS_S between 0.21-2.59 and partial DS_S6 as well as DS_S2 of up to 1 were determined via elemental analysis and ¹³C NMR spectroscopy. Besides, solid-state CP/MAS ¹³C NMR could characterise CS regarding the sulfation. Subsequently, FT Raman investigation of obtained CS was conducted with the aim to establish analysis methods quantifying the total DS_S. The intensities of Raman bands ascribed to the vibrations of OSO and C-O-S groups were used as analysis parameters, yielding calibration curves with high correlation coefficients of more than 0.96.     

A Novel Co(II) Coordination Polymer Assembled from V-shaped 2,3,2’,3’-Thiodiphthalic Acid and N-donor Ancillary Ligand: Syntheses,Structure and Properties

A novel coordination polymer {[Co₂(tdpa)(bpe)_1.5(H₂O)]·(bpe)_0.5·(H₂O)} _n (1) has been hydrothermally synthesized through the reaction of 2,3,2’,3’-thiodiphthalic acid (H₄tdpa) with divalent cobalt salt in the presence of ancillary nitrogen ligand (bpe = trans-1,2-bis(4-pyridyl)ethene) and characterized by IR spectra, elemental analysis and single crystal X-ray diffraction. Due to various coordination modes and conformations of the versatile 2,3,2’,3’-thiodiphthalic acid ligand, the complex exhibits structural and dimensional novelty. In complex 1, metal–organic ribbons (Co-tdpa) are connected together through bpe ligands to generate a three-dimensional (3D) metal–organic framework. The structure of 1 can be described as a (3,6)-connected network with a Schläfli symbol of (4²·6)(4⁴·6¹⁰·8) topology. The thermal stability of the complex 1 was studied by thermal gravimetric analyses (TGA), and the UV?vis absorption property of complex 1 was also investigated.     

Thermogravimetric investigation of the chemical compatibility of graphite and metal oxides

Methods of thermodynamic analysis and gravimetric measurement are used to study graphite and its mixtures with metal oxides heated to 1000°C under nonisothermal conditions. The chemical compatibility of graphite with Al₂O₃, CaO, SiO₂, MgO, Fe₂O₃, TiO₂, Na₂O, and K₂O is investigated. It is shown experimentally that under the given conditions the loss of mass (m /m) in specimens with these additives as reflected by the gravimetric curves does not exceed m /m in a purely graphite specimen.Translated from Ogneupory i Tekhnicheskaya Keramika, No. 12, pp. 12 – 15, December, 1996.     

Imidazole-Containing Ligands Assisted Self Assembly of Two New Cd(II) Coordination Polymers: Syntheses, Crystal Structures and Photoluminescent Properties

Two new coordination polymers, {[Cd₂(PDC)₂(H₂O)₂(L₁)]·2H₂O}_n (1) and {[Cd (2,5-PDC)(H₂O)(L₂)]·H₂O}_n (2), have been obtained from hydrothermal reactions of Cd²⁺ ion with the 2,5-pyridinedicarboxylic acid (H₂PDC) and two imidazole-containing ligands [L₁ = 1,4-bis(imidazol-1-yl)benzene and L₂ = 1,4-bis(1-imidazol-yl)-2,5-dimethylbenzene]. Complex 1 features a three-dimensional 6-connected rob topological net. Complex 2 shows a two-dimensional 6-connected hxl topological net. The structural differences between 1 and 2 demonstrate that the different imidazole-containing ligands play critical roles in the formation of the resulting frameworks. The photoluminescent properties of 1 and 2 have also been investigated.     

UV-photopolymerisation of poly(methyl methacrylate)-based inorganic-organic hybrid coatings and bulk samples reinforced with methacrylate-modified zirconium oxocluster

In this work, we developed and optimised a synthetic route which enables to produce by spray-coating hard, transparent and stable inorganic-organic hybrid coatings for a wide variety of different substrates (e.g. stone, stainless steel, polymethylmethacrylate, polyethylene, wood, anodized aluminum). Chemically and thermally stable acrylate-based hybrid materials embedding the zirconium oxocluster Zr₄O₂(OMc)₁₂, OMc(CH₂C(CH₃)C(O)O) were prepared and UV-cured.The coatings of different compositions on different substrates were characterized by numerous analytical and spectroscopic methods such as FT-IR spectroscopy, Angle Resolved-XPS (AR-XPS), Secondary Ion Mass Spectrometry (SIMS), X-ray Absorption Spectroscopy (XAS), Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-ray analysis (EDX). Bulk samples were also prepared for additional characterizations. The bulk samples were analysed by FT-IR, whereas the cross-linking degree was qualitatively evaluated by swelling experiments. As far as the mechanical properties are concerned, the shear storage modulus (G′) and loss modulus (G″) were measured by Dynamical Mechanical Thermal Analysis (DMTA) technique. Moreover, the best conditions for the curing and cross-linking processes of the hybrid materials were studied up to 200 °C by using Differential Scanning Calorimetry (DSC). The thermal stability of the hybrid samples was evaluated by Thermogravimetric Analysis (TGA).     

Coordination Behaviors and Supramolecular Interactions of 2-(2′-Pyridyl) Imidazoline: Crystal Structure of Its Two Cu(II) Complexes

Two new copper coordination complexes, [Cu(PI)(OX)(H₂O)]·H₂O (1) and [Cu(PI)(fum)(H₂O)]·H₂O (2) [PI = 2-(2′-pyridyl) imidazoline, OX^2? = dianion of oxalic acid and fum^2? = dianion of fumaric acid], were synthesized by interface diffusion method based on Cu(II) ions, PI ligands and aliphatic dicarboxylic acids. Complex 1 is a mononuclear complex which spreads into a 3D (4,9)-connected supramolecular network via hydrogen bond interactions, while complex 2 features a 1D zigzag chain with two different orientations. These two compounds are characterized by single crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, infrared spectra, and thermogravimetric analyses.     

In situ Synthesis,Crystal Structure and Photoluminescence of a Novel Coordination Polymer with (4,6,6)-Connected sqc111 Topology

Employing the mixed ligands to react with Cd(NO₃)₂·4H₂O afforded a new 3D coordination polymer [Cd₃(BPTC)(bmp)₂(ox)(H₂O)₄] (1) (H₄BPTC?=?biphenyl-3,3′,4,4′-tetracarboxylic acid, bmp?=?3,6-bis(imidazol-1-yl)pyridazine, H₂ox?=?oxalic acid), in which ox^2? was from the in situ oxidation of ethanol. Compound 1 bears a novel trinodal (4,6,6)-connected net structure, and it is the first replica of the theoretically predicted sqc111 topology net. Moreover, the thermal and photoluminescent properties for 1 were also investigated.     

Targeted Highly-Thermostable Metal–Organic Frameworks Directed by Imidazole: Syntheses, Structures, Thermal Behaviors and Luminescent Properties

Three new isostructural 3D lanthanide MOFs (Ln(HBPTC)(H₂O)) (Ln = Tb (1), Pr (2), Nd (3); H₄BPTC = 3,3′,4,4′-biphenyltetracarboxylic acid) have been synthesized under hydrothermal conditions using imidazole as a structure-directing agent, and characterized by elemental analyses, IR, thermogravimetric analyses (TGA) and powder X-ray diffraction (PXRD) analyses. Topologically, compounds 1–3 demonstrate an intriguing 3D (6, 6)-connected network with the Schläfli symbol of (4¹⁰·6⁵)(4⁹·6⁶); and if the dinuclear (Ln₂) clusters are considered as the single 8-connected nodes, they can be described as a scarcely reported (4, 8)-connected alb net constructed from two intertwining sqp-4 nets. TGA and PXRD analyses reveal that compounds 1–3 exhibit high thermal stability, at least being stable up to 410 °C. Furthermore, the luminescence studies were performed on compound 1 and its dehydrated phase in the solid state at room temperature. The results demonstrate that compound 1 displays intense green emission, implying its potential application as fluorescence material. And the luminescence of 1 is quenched when removing the coordinated water molecules.     

Structure and performance of a novel TiO2-phosphonate composite photocatalyst

An innovative SiO₂-PO₄³⁻-TiO₂ photocatalyst is presented which is able to bond TiO₂ to Raschig rings (RR). Evidence for the formation on the catalyst surface of PO stretching bands near 1200–1250 cm⁻¹ is presented by FTIR spectroscopy. The TiO₂ Degussa P25 on the catalyst surface (RR) was further characterized by high-resolution transmission electron microscopy (HRTEM), and X-ray diffraction showing that the composite catalyst prepared at 500 °C does not alter the particle size or crystallographic composition of the TiO₂ Degussa P25 particles. The Ti- and P-distribution of the catalyst surface overlayers was obtained by Ar-sputtering eroding up to 100 topmost catalyst layers. By atomic force microscopy (AFM) the root mean square roughness (Rq) or rugosity of 771 nm and an average height of the catalyst layer of 1.52 μm were found on the glass surface. The root mean square roughness Rq varies very little in value before and after the photocatalysis indicating that the sample porosity is conserved during 4-CP photodegradation. The disappearance kinetics of 4-chlorophenol (4-CP) on the SiO₂-PO₄³⁻-TiO₂ composite occurred within 15 min and was faster than the 45 min needed with suspensions of TiO₂ Degussa P25 (1 g L⁻¹). The SiO₂-PO₄³⁻-TiO₂ photocatalyst was able to degrade repetitively 4-CP solutions without loss of activity. The effect of the light intensity, oxidant concentration and 4-CP concentration on the photodegradation kinetics was investigated and is reported in this study.     

First In Situ Raman Study of Vanadium Oxide Based SO2 Oxidation Supported Molten Salt Catalysts

In situ Raman spectroscopy at temperatures up to 500°C is used for the first time to identify vanadium species on the surface of a vanadium oxide based supported molten salt catalyst during SO₂ oxidation. Vanadia/silica catalysts impregnated with Cs₂SO₄ were exposed to various SO₂/O₂/SO₃ atmospheres and in situ Raman spectra were obtained and compared to Raman spectra of unsupported model V₂O₅–Cs₂SO₄ and V₂O₅–Cs₂S₂O₇ molten salts. The data indicate that (1) the V^V complex V^VO₂(SO₄)₂ ^3– (with characteristic bands at 1034 cm^–1 due to (V=O) and 940 cm^–1 due to sulfate) and Cs₂SO₄ dominate the catalyst surface after calcination; (2) upon admission of SO₃/O₂ the excess sulfate is converted to pyrosulfate and the V^V dimer (V^VO)₂O(SO₄)₄ ^4– (with characteristic bands at 1046 cm^–1 due to (V=O), 830 cm^–1 due to bridging S–O along S–O–V and 770 cm^–1 due to V–O–V) is formed and (3) admission of SO₂ causes reduction of V^V to V^IV (with the (V=O) shifting to 1024 cm^–1) and to V^IV precipitation below 420°C.     

Stimuli-responsive conjugated polymers. Synthesis and chiroptical properties of polyacetylene carrying l-glutamic acid and azobenzene in the side chain

A glutamic acid- and azobenzene-containing novel N-propargylamide, (S)-CHCCH₂NHCOCH(CH₂CH₂CO₂CH₂C₆H₅)NHCO₂CH₂CH₂-p-C₆H₄NNC₆H₅ (1) was synthesized and polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] as a catalyst to obtain the corresponding polymer [poly(1)] with the moderate number-average molecular weight of 12,200 in 93% yield. The chiroptical studies revealed that poly(1) took a helical structure in THF, CHCl₃, CH₂Cl₂ and toluene. Poly(1) underwent solvent and heat-driven helix-helix transition. The trans-azobenzene of the side chain isomerized into cis upon UV-irradiation, accompanying decrease in helicity. The cis-azobenzene moiety reisomerized into trans upon visible-light irradiation, while the polymer did not recover the original helicity.