Titanium Chelates Research Articles

Synthesis, spectral elucidation, thermal study, DFT calculations and biological application of new nano sized coordination compounds of a barbiturate based ligand

Novel titanium (IV), vanadyl (II), nickel (II), copper (II), cobalt (II), mercury (II) and silver (I) coordination compounds were established from a ligand created from a diazotization coupling process between 1-(4-aminophenyl)ethanone and barbituric acid. Analytical, spectroscopic, and thermal approaches were used to detect the best structural geometry of the compounds. The coordination compounds were constructed with (1M:2L) stoichiometry. With the exception of titanium (IV), vanadyl (II), and silver (I), all chelated compounds were non-electrolytes. Except for the vanadyl complex, which possessed square pyramidal geometry, and the silver one with tetrahedral geometry, the chelates of titanium (IV), copper (II), nickel (II), mercury (II) and cobalt (II) possessed an octahedral one. The ligand functioned as an ON-neutral bidentate moiety. The thermal manner of all compounds was studied by thermogravimetric analysis (TGA). According to XRD and TEM analysis, all compounds were nanosized. Theoretical calculations were performed to gain more information about the structure of the ligand and Ag chelate by DFT/B3LYP/LanL2DZ. The ligand and some of its chelates were explored as antibacterial, antifungal, and antitumor agents. According to the findings, the (H2L) activity was enhanced by complexation. The antitumor activity of the Ag(I) chelate was dramatically higher than that of the ligand and other chelates, with an IC50 of 11.5 gmL-1. For antimicrobial, Cu(II) chelate outperformed other complexes and the control drug against A. brasiliensis, B. cereus and P. vulgaris.

Effect of titanium chelating compound on hydration resistance of CaO material

AbstractThe hydration resistance of CaO materials prepared by Ca(OH)2 calcination with titanium chelating compounds is investigated in this paper. The crystalline phases and microstructure characteristics of sintered specimens were studied by X‐ray diffraction (XRD), define FTIR spectroscopy, scanning electron microscopy (SEM), and energy dispersive spectrometer (EDS). The results showed that the hydration resistance of CaO samples was improved significantly, especially for samples with 9 wt% Ti chelating compound. The specimens with Ti chelating compound showed an increase in bulk density and a decrease in apparent porosity after heating when compared to the specimens without additive. The grain surface of CaO grain and the gaps between the CaO grain boundaries were covered with calcium phosphate glass phase, calcium phosphate showed two different shapes: irregular shape and rod shape. The formation and distribution of these two forms were the key factors that affecting the hydration resistance of CaO samples.

Biocompatible titania hydrogels with chemically triggered release of a photosensitive dye

5,10,15,20-Tetrakis(4-sulfonatophenyl)porphyrin was entrapped into biocompatible hydrogels formed by self-assembling micelles of the titanium dioxide prepared by hydrolysis of titanium ethoxide modified with triethanolamine (TEA). The materials were characterized by their optical and photosensitive properties. The immobilization led to changes of the absorption spectra of the dye and decreased its molar absorption coefficient. The TiO2 matrix did not degrade the entrapped porphyrin upon u.v. irradiation. The formation of TEA–titanium(IV) chelates facilitated a controlled and triggered release of the immobilized dye from the hydrogels in lactate and citrate buffers. The released dye prolonged the sterility of citrate–phosphate buffer and its illumination with visible light inhibited growth of Aspergillus niger.

Tailor‐Made Mesoporous Ti‐SBA‐15 Catalysts for Oxidative Desulfurization of Refractory Aromatic Sulfur Compounds in Transport Fuel

AbstractWe propose large‐pore titanium‐containing organosilylated mesoporous silica (Ti‐SBA‐15) as a highly efficient catalyst for the oxidative desulfurization (ODS) of refractory aromatic sulfur compounds with the aim to produce ultra‐low sulfur diesel. To achieve this, we synthesized a series of mesoporous Ti‐SBA‐15 catalysts according to a new procedure. The procedure is based on the controlled grafting of titanium chelates on SBA‐15 silica at low temperatures (5 °C). This specific synthesis procedure ensured a high dispersion of the required 4‐coordinate tetrahedral Ti4+ sites located on the mesopore surface. To substantiate the influence of the titanium content and mesopore size on the ODS performance of the catalysts, the parameters were varied in the range of 0.7 to 4.7 mol % (Si/Ti) and 5.1 to 9.0 nm, respectively. The resulting Ti‐SBA‐15 catalysts were then tested in the oxidative desulfurization (ODS) of model sulfur‐containing compounds in the presence of cumene hydroperoxide (CHP) as the organic oxidant. The ODS of a real industrial diesel fuel was also carried out in a continuous fixed bed reactor with the same Ti‐SBA‐15 catalysts and CHP. The catalytic results revealed that the Ti‐SBA‐15 catalysts with the largest pore sizes (>7.3 nm) and highest Ti contents (>2.8 mol %) were highly active catalysts for ODS reactions. Moreover, the catalysts with large pores and high Ti loadings appeared to be stable for over 30 h and were far less prone to deactivation than their equivalent Ti‐SBA‐15 samples with smaller pore diameters and lower Ti contents.

Controlled Postgrafting of Titanium Chelates for Improved Synthesis of Ti-SBA-15 Epoxidation Catalysts

A new synthesis procedure that is based on the grafting of titanium alkoxide species chemically modified by acetylacetone (acac) on the surface of a P123/SBA-15 composite material is proposed to prepare Ti-SBA-15 catalysts and studied by a combination of elemental analysis, Fourier transform infrared spectroscopy (FTIR), solid-state 13C (CP) NMR, thermogravimetric analysis (TGA), X-ray diffraction (XRD), diffuse reflectance UV−vis (DR-UV−vis), and N2 physisorption at −196 °C. In the absence of the acac chelates, the observed formation of anatase TiO2 onto the surface of the material demonstrates that the coordinating ligand acts as an inhibitor for the crystallization of anatase. Furthermore, FTIR and 29Si NMR results show that the chelated titanium alkoxide precursor interacts strongly with the silanol groups, which, in turn, greatly enhances the dispersion of the titanium species in the mesoporous silica matrix. Moreover, a decrease of the temperature applied for the postgrafting and an increase of both the acac/Ti ratio and pH are shown to favor the retention of titanium on the materials surface without affecting the titanium dispersion. According to the X-ray photoelectron spectroscopy (XPS) results, a maximal titanium content of 13.8% can be well-dispersed on the surface of the mesopores without formation of an excess on the external surface of the solids. However, the results of the DR-UV−vis analyses and the catalytic epoxidation of cyclohexene reveal that the maximal concentration of titanium species in tetrahedral coordination is obtained for materials with a Ti/Si ratio of 5.6%. Even if materials with higher titanium content do not show higher conversion of cyclohexene, they do exhibit remarkably low catalytic deactivation during the recycling tests. A higher hydrothermal stability is suggested as an explanation for the lower deactivation of Ti-SBA-15 at high titanium content.

Waste-Reducing Catalysis for Acylation of a Secondary Amine: Synthesis of DEET

Mixed oxide catalysts were studied for a model acylation – m-toluic acid reacting with diethylamine to N,N-diethyl-3-methylbenzamide (DEET) – and compared to standard homogeneous catalysts such as titanium chelates. More acidic catalysts such as hydroxyapatites and supported 12-tungstophosphates were active, stable in a gas phase, and selective with stoichiometric feeds. Optimal results (long-term MTA conversion of 78 ± 6%, DEET selectivity of 86 ± 3% at WHSV = 3–9 h−1, no deactivation over 100 h) were obtained with a supported 12-tungstophosphate at 573 K, 0.1 MPa.

Synthesis and characterization of titaniumnaphthoquinolates and their [ 4+2]-cycloadducts

The titanium chelates of naturally occurring hydroxy-1,4-naphthoquinones have been synthesized and their [4+2]-cycloadditions with 1,3-dienes have also been investigated.

Retro-Claisen Cleavage of the β-Dicarbonyl Ligand in Alcoholysis of Group IVB Metal Chelates

Chelates of titanium, zirconium, and hafnium with β-dicarbonyl compounds react with butyl, amyl, and octyl alcohols to give metal alkoxides. The reaction is accompanied by retro-Claisen cleavage of the ligand. The reactivity of the chelates was studied in relation to the ligand structure, nature of the metal, and reaction temperature. The reaction mechanism is discussed.

ジエチルアミノ置換ヒドロキシベンジリデンアニリン誘導体を配位子とするチタンおよびケイ素キレート錯体の合成と性質

シッフ塩基としてジエチルアミノ置換ヒドロキシベンジリデンアニリン類を配位子とするチタンおよびケイ素キレート錯体を合成し, 熱安定性, 可視吸収スペクトル, 有機溶媒への溶解性に及ぼす置換基の影響を検討した。チタンあるいはケイ素キレート錯体は2-ヒドロキシー4-ジエチルアミノーN- (2-ヒドロキシベンジリデン) アニリン類とチタンテトライソプロポキシドあるいは四塩化ケイ素を反応させることにより合成し, チタンキレート錯体は黒色, ケイ素キレート錯体は暗赤色の粉末として得られた。これらの錯体はアミン成分の芳香環にジエチルアミノ基を導入することにより, 吸収極大波長はかなり長波長シフトし, 有機溶媒への溶解性はかなり増加したが, 熱分解温度は低下した。さらにケイ素キレート錯体は蛍光性を示した。

ヒドロキシベンジリデンアニリン類およびそのナフチル導入誘導体を配位子とするチタンキレート錯体の合成と性質

シッフ塩基として2-ヒドロキシ-N- (6-クロロ-2-ヒドロキシベンジリデン) アニリン類およびそのクロロフェニル部にナフチル基を導入したアゾメチン類を配位子とするチタンキレート錯体を合成し, 熱安定性, 可視吸収スペクトル, 有機溶媒への溶解性に及ぼす置換基の影響を検討した。6-クロロベンジリデンアニリン類を配位子とする錯体の熱安定性は, 配位子の芳香環にニトロ基を導入することにより向上し, メチル基を導入することにより低下する傾向があり, 有機溶媒への溶解性と関連し, 溶解性が減少すると向上する傾向を示した。一方, 配位子の芳香環としてナフチル基を導入することにより錯体は, 吸収極大波長や吸収端がかなり長波長にシフトし, 有機溶媒への溶解性は相当するフェニル基をもつ配位子の錯体と同様に低いが, 熱安定性は400℃以上の高い安定性を示した。

Improvements in the application properties of water-based low VOC coatings

This paper discusses a new class of acrylic latex (NeoCryl TX200) in which the colloid stabiliser is designed to interact with titanium chelates such as Tilcom AT23, thereby building up a weak gel structure which can be broken down by shear. This class of latex can be formulated with associative thickener (and their blends) in conjunction with titanium chelates, thus providing considerable formulation flexibility which cannot be achieved with conventional surfactant stabilised acrylic latex. A key feature of this new class of latex is that the colloid stabilisation system does not introduce water sensitivity, and indeed wet adhesion characteristics are fully comparable to those of state of the art adhesion promoted latexes. A further benefit of this class of latex is that of increased open-time, arising in part from its intrinsic rheological characteristics, and in part from the high film build achievable with thixotropic formulations. Rheological measurements show that introduction of titanium chelates greatly increases the low shear-rate viscosity of the system, and vane rotor measurements show that there is a near linear dependence of gel strength with titanate concentration. This gel, which is responsible for preventing in-can settlement of pigments and good brush pick-up, is partially broken down by the action of brush dripping, and is completely broken down during application (eg by brush or spray). The structure subsequently builds up with time, with gelation occurring in as little as 5–10 minutes, but with full recovery of gel strength taking in the region of 10–12 hours. The titanate chelating agent, even at high concentrations, does not contribute to the high shear-rate viscosity of the system, this being controlled by the addition of associative tickeners, either alone or in combination. The associative thickener(s) also control the low shear-rate viscosity during the period in which the gel structure has been sheared out, and thus good flow and levelling properties can be obtained through the optimisation of associative thickener type(s) and concentration(s). Although, as might be expected, cosolvents affect the rheological properties of formulations containing both associative thickener and titanium chelate, this effect is not a large one, and can be readily taken into account during formulation design.

Molecular Mechanics Calculations on Chelates of Titanium(IV), Vanadium(IV/V), Copper(II), Nickel(II), Molybdenum(IV/V), Rhenium(IV/V) and Tin(IV) with Di- and Tridentate Ligands Using the New Extensible Systematic Force Field (ESFF)—An Empirical Study

Force field calculations were performed on a series of 27 transition metal complexes of titanium(IV), vanadium(IV/V), copper(II), nickel(II), molybdenum(IV/V), rhenium(IV/V), and tin(IV) with a broad variety of di- or tridentate ligands in order to find a reliable scheme for determining the molecular structure of such chelates with the new Extensible Systematic Force Field (ESFF). A good agreement between theoretical results and experimental data was achieved. In some cases an unspecific fitting of the force field was necessary.

Fire-resisting properties in several TiO2 wood-inorganic composites and their topochemistry

A study of the wood-inorganic composites prepared by the sol-gel process with a metal alkoxide indicated that an inorganic modification of wood with TiO2 gels from tetraisopropoxytitanium (TPT) can not improve its properties due to the formation of the gels in the cell lumina by high hydrolysis rate of TPT. In this study, therefore, titanium alkoxides or titanium chelates which have the lower rate of hydrolysis and subsequent polycondensation than TPT were used for preparing TiO2 wood-inorganic composites to study the topochemical effects of the TiO2 gels for the property enhancement of wood. As a result, it was found by SEM-EDXA analysis that the TiO2 gels deposited within the cell walls could improve the properties of wood in dimensional stability and fire-resistance, whereas for the gels in the cell lumina, property enhancement could not be achieved, as observed in SiO2 wood-inorganic composites.

Theoretical Studies of Ethylene Polymerization Reactions Catalyzed by Zirconium and Titanium Chelating Alkoxide Complexes

Ethylene polymerization catalyzed by zirconium and titanium chelating alkoxide complexes has been studied using a density functional method. Activation barriers of 6.4 and 7.4 kcal/mol are found for the titanium and zirconium sulfur-bridged catalysts, respectively. The Zr/Ti CH2- and directly-bridged catalysts have higher insertion barriers of 10−15 kcal/mol. For the S-bridged systems, there is a strong interaction between the metal and the sulfur bridge, which leads to a less stabilized π-complex and a lower activation energy. The larger exothermicity to the γ-agostic direct product by 5 kcal/mol in the titanium case compared to zirconium for all three catalysts (S-, CH2-, and directly-bridged) is suggested to be one of the reasons why the barriers for titanium are lower than for zirconium. Flexible ligands with the ability to donate may be one method for developing more active alternative catalysts as the flexible ligand competes with the approaching olefin. The more weakly bound olefin leads to a lower activation barrier.

13C-CP/MAS-NMR spectroscopy of tridentate diacidic ligands and their titanium(IV) chelates. molecular structure of bis[benzoylacetone thiobenzoylhydrazonato(2-)]titanium(iv)

A series of tridentate diacidic ligands having the donor set ONO(S) as well as the corresponding titanium(IV) chelates were studied by13C-CP/MAS-NMR spectroscopy. Structural changes caused by the complex formation are discussed. The crystal structure of bis[benzoylacetone thiobenzo-ylhydrazonato(2-)]titanium(IV) was determined by X-ray analysis as to be distorted trigonal prismatic. Orthorhombic space group Pca2l,Z=4, 3304 observed independent reflections, unit-cell parameters at 298 K:a=22,808(2) a,b=13,073(4) a,c=10,450(4) a.

アゾおよびアゾメチン化合物を配位子とするチタンキレート錯体の合成と熱分解

新規な反応性錯体化合物として, アゾおよびアゾメチン化合物を配位子とする2-ヒドロキシ型チタンキレート錯体の合成とその熱分解を検討した。チタンテトライソプロポキシドは2当量の2-ヒドロキシアゾおよびアゾメチン化合物と定量的に反応し, チタンキレート錯体を生成した。これら錯体は, 分解点が102～115℃で熱安定性が低く, また容易に加水分解した。これらの性質は, これまでに報告している2, 2'-ジヒドロキシアゾおよびアゾメチン化合物を配位子とするキレート錯体がきわあて高い熱安定性と加水分解安定性を有しているのとは著しく異なっている。本実験で得られたキレート錯体を減圧下で熱分解した結果, 揮発成分として2-プロパノールとアセトンが生成し, 一方残渣として黒色の固体が得られた。この固体をTHFとヘキサン (1 : 10 (V/V)) で再沈殿して単離した熱分解生成物は, 配位子とチタンを構成成分とする分子量Mw2000～3700のポリマーであることがわかった。

N-ベンジリデンアニリンのヒドロキシ誘導体を配位子とするチタンキレート錯体の合成と性質

N-ベンジリデンアニリンのヒドロキシ誘導体を配位子とする種々のチタンキレート錯体の合成とその性質を検討した。ベンジリデンアニリンの-CR=N-部の置換基RにH, CH3, C2H5をもち, アニリン部の4-位 (または5-位) の置換基XにCH3, NO2, C6H5をもっ新規チタンキレート錯体を芳香族アミンとアルデヒドやケトンおよびチタンアルコキシドとをワンポット反応させることにより合成した。これらのチタンキレート錯体は榿色系の色相を有し, 特に, 置換基RとしてCH3またはC2H5をもち, 置換基Xをもたないか5-位にCH3をもっチタンキレートは有機溶媒に対する溶解性が高かった。 RにCH3, C2H5をもっチタンキレートの熱分解温度は230～310℃で, Rに置換基をもたないキレートに比べて低かった。

2-ヒドロキシ-N- (5-クロロ-2-ヒドロキシベンジリデン) アニリン類を配位子とするチタンキレート錯体の合成と性質

シップ塩基として2-ヒドロキシ-N- (5-クロロ-2-ヒドロキシベンジリデン) アニリン類を配位子とするチタンキレート錯体を合成し, 熱的安定性, 可視吸収スペクトル, 有機溶媒への溶解性に及ぼす置換基の影響を検討した。得られたチタンキレート錯体は褐色もしくは黒色系の色調を呈し, 熱的安定性は配位子のアミン成分の芳香環にニトロ基あるいはメチル基を導入することにより向上し, クロロ基やフェニル基およびナフチル環を導入することにより低下する傾向があるが, 溶解性は配位子成分にフェニル基やナフチル環を有する錯体で向上する傾向を示した。

Chelation-controlled protocol for the diastereoselective reduction of ketones

A new chelation-controlled, α-chiral ketone reduction protocol is presented based on titanium tetrachloride and a wide variety of reducing agents. Features of the proposed intermediate titanium chelates necessary to obtain high diastereoselectivity are discussed

Determination of acetylacetone and alcohols in titanium chelates

Acetylacetone (2,4-pentanedione) and alcohols in titanium chelates have been determined by gas chromatography of the solvolyzed chelate. For the determination of acetylacetone, the tithanium chelate is cleaved with acetic acid at 140–150°C for 2–4 h in a closed system. The acetylacetone liberated is determined by capillary gas chromatography as the trimethylsilyl derivative. Normal alcohols elute as acetates, isoproyl alcohol elutes as a mixture of the corresponding acetate and trimethylsilyl derivative. The cleavage of a titanium chelate with acetic anhydride by heating at 130°C for 2 h converts alcohols, including isopropyl alcohol, quantitatively to their acetates which elute as a single peak for each alcohol. Acetylacetone decomposes partially under these conditions and the acetic anhydride method is useful only for the determination of alcohols.