Synthesis and thermal evolution of TiO2-RuO2 xerogels

Gels of the Ti Ru O system, where , 0.001, 0.01, 0.02, 0.05, 0.1, 0.15, 0.2, 0.3 and 0.5 (mol), have been synthesized by a polymeric sol-gel route from Ti (IV)-iso-propoxide and Ru (III) acetyl-acetonate (acac). The mechanisms of the hydrolysis and polycondensation reactions were studied by using Fourier Transform Infrared Spectroscopy (FTIR). The evolution of the xerogels as a function of temperature was also determined. At temperatures, as low as 200°C, mixtures of antase Ti Ru O (Ass) solid solution and rutile Ti Ru O solid solution (Rss) were attained for compositions with 0.3. For , only the anatase phase is present (A) and for , mixtures of anatase Ti Ru O (Ass) solid solution, rutile Ti Ru O solid solution (Rss) and Ru Ti O (RuO ss) solid solution were attained. RuO catalyzes the anatase to rutile transformation, even at RuO contents as low as 0.001 mol. Although, from 300 to 400°C the solid solubility of RuO into rutile-TiO phase is located at , from 500°C that value is located in the 0.05 range. This fact could be due to the metastability of the rutile solid solutions containing ruthenium oxide above 400°C. According to semiquantitative transmission electron microscopy-energy dispersive X-ray spectroscopy (TEM-EDX) analyses, at 700°C, there are compositional variations in both solid solutions, Rss and RuO ss. Thus, the system is chemically heterogeneous. The amount of Ti ions hosted into the RuO lattice in the solid solution is lower than that of Ru ions into the rutile-TiO lattice. At this temperature, the contents of these solid solutions are mol% RuO into the TiO lattice (the maximum value found) and around 8.0 mol% TiO (the maximum value found) into RuO . The RuO volatilization can promote the segregation of the ruthenium oxide giving rise to the heterogeneity and the metastability observed in this system.     

Solid State Supramolecular Complexes [Hg<Subscript>6</Subscript>As<Subscript>4</Subscript>](CuX<Subscript>3</Subscript>)<Subscript>2</Subscript> (X <Emphasis Type="Bold">=</Emphasis> Cl,Br): One-Dimensional Helical Guest in a Three-Dimensional Host Framework

Two new supramolecular complexes, [Hg₆As₄](CuBr₃)₂ (1) and [Hg₆As₄](CuCl₃)₂ (2), have been synthesized and their crystal structures have been determined. Compound 1 crystallizes in the monoclinic system, space group I2/a (No. 15), with the unit cell dimensions a = 14.884(3), b = 9.358(2), c = 20.413(4) Å, β=92.88(3)°, and Z = 6. The crystal structure is comprised of the three-dimensional [Hg₆As₄]⁴⁺ polycationic framework hosting one-dimensional 6-step helical (CuBr guest chains built of the [CuBr₄] tetrahedra sharing two of their vertexes. The complex 2 exhibits a distorted variant of the same type of crystal structure (space group I2/a, a = 14.690(1), b = 9.1851(7), c = 20.285(1) Å, β=92.170(1), and Z = 6) that is characterized by a multifarious positioning of the guest anions in the cavities of the perfectly ordered [Hg₆As₄]⁴⁺ host framework. Structures of the title supramolecular assemblies and the previously reported silver-containing analogue [Hg₆As₄](AgCl₃)₂ are discussed taking into account the principles of host–guest complementarity.     

Studies on a new dinuclear Co<Superscript>II</Superscript>–pterin complex exhibiting reactivity towards phenylalanine and bromobenzene

2-Pivaloylamino-6-acetonyl-isoxanthopterin (1, ) has been reacted with under suitable conditions for synthesizing the new compound ] (2). It has been characterized by elemental analysis, electrospray ionization mass spectrometry, magnetic susceptibility measurement, different spectroscopic techniques, and cyclic voltammetry. Molecular mechanics (MM2) method provided with its optimized geometry (having lowest steric energy), consistent with the above data; the optimized bond lengths and bond angles data tally with the literature X-ray structural data. Reactivity of (2) towards phenylalanine in the presence of in methanol has been followed both kinetically and stoichiometrically; a reasonable amount of tyrosine could be recovered from the reaction medium. The negative value (−274.0 J mol⁻¹ indicates an associative pathway for this process. (2) is also able to react with bromobenzene as indicated by time-dependent absorption spectra as well as product identification. Efficacy of the pterin ligand residue of (2) in rendering the latter reactive towards the above-mentioned organic compounds, has been discussed on the basis of experimental evidence.     

An <Emphasis Type="Italic">ab initio </Emphasis> Quantum-Chemical Study of C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CH<Subscript>3</Subscript> and C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CF<Subscript>3</Subscript>

The potential functions of internal rotation around the C -S bond in the C₆H₅S(O)CH₃ and C₆H₅S(O)CF₃ molecules were obtained by ab initio MP2(full)/6-31+G* calculations. The stationary points were identified by solving the vibrational problems. The structures in which the plane of the C -S-C bonds is approximately perpendicular to the benzene ring plane correspond to the energy minimum. The barriers to rotation around the C -S bond, corrected for the zero-point vibration energy, are 21.29 [C₆H₅S(O)CH₃] and 28.98 [C₆H₅S(O)CF₃] kJ mol⁻¹. The bond angles (deg) are as follows: 95.7 (CSC), 107.1 (C SO), 106.3 (C SO) in C₆H₅S(O)CH₃; 93.5 (CSC), 108.2 (C SO), 105.2 (C SO) in C₆H₅S(O)CF₃. The bond lengths are as follows (Å): 1.520 (S=O), 1.804 (C -S), 1.810 (C -S) in C₆H₅S(O)CH₃; 1.507 (S=O), 1.799 (C -S), 1.870 (C -S) in C₆H₅S(O)CF₃. According to the results of NBO calculations, the formally double S=O bond consists of a strongly polarized covalent σ bond (S→O) and an almost ionic bond. An increase in the S=O bond multiplicity relative to a single bond is mainly due to hyperconjugation by the mechanism n(O)→σ*(C -S) and n(O)→σ*(C -S) and, to a lesser extent, by interaction of the oxygen lone electron pairs with the Rydberg orbitals of the S atoms, characterized by a large contribution of the d component.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 96–104.Original Russian Text Copyright © 2005 by Bzhezovskii, Il’chenko, Chura, Gorb, Yagupol’skii.     

Surface chemical and physical properties of TEOS-TBOT-PDMS hybrid materials

The application of nitrogen adsorption, mercury porosimetry and inverse gas chromatography (IGC) for the examination of surface physical and chemical properties of hybrid materials is discussed. Hybrid materials were prepared from tetraethoxysilane (TEOS), tetrabutyl orthotitanate (TBOT), and hydroxyl terminated polydimethyl siloxane (PDMS) for different TBOT concentrations. It was found that TBOT affects specific surface areas, pore volumes and pore sizes, but does not affect pore morphology. Surface chemical properties were analyzed by IGC. It was found that the dispersive surface energy was a function of the material pore size. Values between 36 and 42 mJ···m^-2 were obtained for the dispersive surface energy which are consistent with those of hybrid materials. On the other hand, the acid-base (k , k ) surface constants showed good correlation with the TBOT concentration. These materials can be considered as anphoteric ones, and it was found that k increases from 1.07 to 1.47, and k increases from 0.76 to 1.73 when the TBOT concentration increases from 0 to 7%. Such increase is assigned to the formation of Si–O–Ti bonds as it was deduced from an IR band appearing at 930 cm^-1 in the FT-IR spectra.     

Synthesis, characterization and redox properties of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,3- bis (2-carboxyaldehyde phenoxy)propane and its CuII, NiII, PbII, CoIII and LaIII complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:,14,15-tribenzo-9,13-dioxacyclohexadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine and 1,3-bis(2-carboxyaldehyde phenoxy)propane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by a template effect by reaction of 2,6-diaminopyridine and 1,3-bis (2-carboxyaldehyde phenoxy)propane and Cu O, Ni O, Co O, La O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H- and ¹³C-NMR-, UV-vis spectra, magnetic susceptibility, conductivity measurements, mass spectra and cyclic voltammetry. All complexes are diamagnetic and the Cu^II complex is binuclear. The diamagnetic behaviour of the binuclear complex may be explained by a very strong anti-ferromagnetic interaction in the Cu–Cu pair. The Co^II was oxidised to Co^III.     

The Formation and Stability of the [FePy3Cl3]· Py Clathrate in the Pyridine–Iron(III) Chloride System: Phase Diagram and Solid–Gas Equilibria Study

The phase diagram of the pyridine–iron(III) chloride system has been studied for the 223–423 K temperature and 0–56 mass-% concentration ranges using differential thermal analysis (DTA) and solubility techniques. A solid with the highest pyridine content formed in the system was found to be an already known clathrate compound, [FePy₃Cl₃]·Py. The clathrate melts incongruently at 346.9 ± 0.3 K with the destruction of the host complex: [FePy₃Cl₃]·Py_(solid)=[FePy₂Cl₃]_(solid) + liquor. The thermal dissociation of the clathrate with the release of pyridine into the gaseous phase (TGA) occurs in a similar way: [FePy₃Cl₃]·Py_(solid)=[FePy2Cl₃]_(solid) + 2 Py_(gas). Thermodynamic parameters of the clathrate dissociation have been determined from the dependence of the pyridine vapour pressure over the clathrate samples versus temperature (tensimetric method). The dependence experiences a change at 327 K indicating a polymorphous transformation occurring at this temperature. For the process in the range 292–327 K, ΔH =70.8 ± 0.8 kJ/mol, ΔS =197 ± 3 J/(mol K), ΔG =12.2 ± 0.1 kJ/mol; in the range 327–368 K, ΔH =44.4 ± 1.3 kJ/mol, ΔS =116 ± 4 J/(mol K), ΔG =9.9 ± 0.3 kJ/mol.     

The graphical representation of equilibrium for the isothermal and isobaric reactions of ideal gases

The equilibrium for the isothermal and isobaric reactions of ideal gases is investigated in virtue of the intuitionistic figure. The curve is similar to the curve of tangential function which has one inflection and two vertical asymptotes. The equation only has one root ξ _e and it is suitable to find ξ _e by dichotomy. For non-inert substance, when or x_i^0 $$" align="middle" border="0"> , to increase substance i will make an equilibrium shift in the direction to deplete substance i; when {\nu_i} \mathord{\left/ {\vphantom {{\nu_i} {\sum_i {\nu _i}}}} \right. \kern-\nulldelimiterspace} {\sum _i {\nu _i}}> 0$$" align="middle" border="0"> , to increase substance i will make an equilibrium shift in the direction to produce more substance i.     

Thermodynamics of Solutions of Trimethyl Aluminum and Trimethyl Gallium with Tetramethyl Tin

The enthalpies and entropies of evaporation of Al(CH₃)₃–Sn(CH₃)₄and Ga(CH₃)₃–Sn(CH₃)₄solutions were determined. It was established that solvates are formed in these systems and that the dissociation energies of specific interactions in them change in the following order: (10.3) > > > (4.08 kJ mol^–1), (6.52) > (5.14) > > (4.08 kJ mol^–1).     

Synthesis,characterization and DNA binding studies of ruthenium(II) complexes: [Ru(bpy)<Subscript>2</Subscript>(dtmi)]<Superscript>2+</Superscript> and [Ru(bpy)<Subscript>2</Subscript>(dtni)]<Superscript>2+</Superscript>

Two new ruthenium(II) polypyridyl complexes (1) (dtmi = 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-methoxylisatin) and (2) (dtni = 3-(pyrazin-2-yl)-as-triazino[5,6-f]-5-nitroisatin) have been synthesized and characterized by elemental analysis, FAB-MS, ES-MS and ¹H-n.m.r. The DNA-binding patterns of complexes were investigated by spectroscopic titration, viscosity measurements and thermal denaturation. The results indicate that the complexes (1) and (2) interact with calf thymus DNA (CT-DNA) by intercalative mode. Due to the withdrawing electronic substitutent in the intercalative ligand, ptni, the DNA-binding affinity of the complexes (2) is larger than that complex (1) does.     

Iodine Hydrolysis Equilibrium

The equilibrium constant for the hydrolytic disproportionation of I₂

Preparation of highly (111)-oriented (Pb,La)(Zr,Sn,Ti)O<Subscript>3</Subscript> (PLZST) antiferroelectric thin films by modified sol-gel process using a novel tin source,dibutyloxide of tin

Highly (111)-oriented Pb_0.97La_0.02Zr_0.85Sn_0.13 Ti_0.02O₃(PLZST) antiferroelectric thin films were deposited on Pt(111)/Ti/SiO₂/Si(100) substrates through a modified sol-gel process technique. The electric field-induced antiferroelectric-to-ferroelectric (AFE‐FE) phase transformation behaviour was examined by C-V measurement. The results indicated that antiferroelectric (AFE) to ferrroelectric (FE) switching field , FE to AFE switching field were 315 kV/cm and 240 kV/cm respectively. The temperature dependence of the dielectric constant showed that the Curie temperature (T _c) of the PLZST antiferroelectric thin films was 171°C. The voltage dependent current density of the highly (111)-oriented PLZST film was less than 1.3 × 10⁻⁶ A/cm² over electric field range from 0 to ± 427 kV/cm.     

P,N-Bidentate Phosphorus Derivatives of (S)-Prolinol

Phosphorylation of (S)-prolinol with P(NEt₂)₃was used to synthesize aminophosphite (2R,5S)- , which was reacted with the corresponding amino alcohols to afford (2S,5R)- (Va) and (2S,5R)- (Vb). Reaction of Vawith [Rh(CO)₂Cl]₂(P/Rh = 1) yields the mononuclear chelate [Rh(CO)(P^N)Cl] (VIIa), while the analogous reaction with Vbresults in a mixture of products with cis- and trans-orientation of the coordinated phosphorus and nitrogen atoms. Spectral characteristics of the products of coordination of ligands Vaand Vbwere compared with those for the binuclear reference complex [Rh(CO)(L)Cl]₂(VIII), where L is P-monodentate ligand (2S,5R)- (VI). The ligands and complexes were studied by IR, NMR, ³¹P and ¹³C spectroscopy, mass spectrometry, and elemental analysis methods. X-ray diffraction analysis of crystals VIIIwas performed.     

Preparation and Spectroscopic Characterization of Two Manganese(II)semiquinone Complexes

Summary. The complexes [CTA][Mn(II)(SQ)₃] were isolated in the solid state and purified. SQ is the o-semiquinone of L-dopa or dopamine and CTA is the cetyltrimethylammonium cation. These complexes were characterized by Raman, infrared, EPR and thermogravimetry (TG) techniques. The EPR spectra of the solids presented an intense signal characteristic of the o-semiquinone radical anion with g=2.0062 and g=2.0063 for L-dopa and dopamine, respectively. Six characteristic lines around the organic radical signal confirm the presence of the Mn²⁺ ion. The most intense Raman bands were observed at for dopamine and at 1356 cm^–1 for L-dopa and assigned to a C–O stretching with major C₁–C₂ character. The absence of an intense Raman band at ca. , characterizes the ligands as an o-semiquinone radical anion. Broad bands in the region can be assigned to deformations associated with the five-member ring chelate including the manganese ion, the oxygens, and the C₁–C₂ bonds. The more intense IR bands for the dopamine and the L-dopa-derived ligands at are assigned to CO. Mass loss mechanisms for the two complexes, based on the TG results, were proposed and confirm the formula proposed.     

Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

A novel series of 16-membered binuclear complexes of octaazatetraimine ligand, [M = Mn^II, Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃] have been synthesized by metal template condensation reactions of o-phenylenediamine with N,N′-diacetylhydrazine in 1:1:1 molar ratio in methanol. The proposed stoichiometry and the bonding of the macrocyclic moiety to metal ions along with the overall stereochemistry have been derived from the results of elemental analyses, magnetic susceptibility, conductivity data and the spectral data revealed from FT-IR, , ESI mass, UV–visible studies. An octahedral geometry has been envisaged for Mn^II, Co^II, and Ni^II complexes while a slight distortion in octahedral geometry has been noticed for Cu^II complexes. The low conductivity data of all the complexes suggest their non-ionic nature.     

Applications of FT Raman Spectroscopy and Micro Spectroscopy Characterizing Cellulose and Cellulosic Biomaterials

FT Raman spectroscopy and micro spectroscopy were used for the investigation of cellulose, cellulose derivatives and cellulosic plant fibres. Lattice structures of cellulose, polymorphic modifications I and II, as well as amorphous structure, were clearly identified by means of FT Raman vibrational spectra. Chemometric models were developed utilizing univariate calibration as well as methods of multivariate data analyses of FT Raman spectral data for the fast prediction of cellulose properties. Cellulose properties like the degree of crystallinity Xc_Raman, the degree of substitution DS_CMC, DS_AC and cellulose reactivity were determined. In situ/ in vivo FT Raman micro spectroscopy was used for the characterization of cellulose structures of flax and hemp fibres. Orientational and stress dependent FT Raman experiments were carried out.     

CVD-Titania on Mesoporous Silica Gels

Different amounts of CVD-titania ( from 2.3 to 19.2 wt%) with amorphous and crystalline (anatase) phases were synthesized on silica gels (Kieselgel 40, 60, and 100) and characterized by means of XRD, IR, DTG, and adsorption methods. The amounts of titania depend strongly on the pore size distribution of the support, as the narrower the pores, the lower the deposit concentration due to diminution of the accessibility of narrower pores and deceleration of titania grafting in them. A portion of CVD-titania filling matrix pores is rather amorphous than that forming on the outer (external) surfaces of silica gel grains, as anatase crystallites have the average size of 70 nm for KG 40/TiO₂ ( = 6.5 wt% including 26% of anatase and 74% of amorphous titania), 21 nm (KG 60/TiO₂ at = 11 wt%, 16% anatase) and 16 nm (KG 100/TiO₂ at = 19.2 wt%, 29% anatase), which are larger than the average pore size of the silica gels. The crystallite size decreases with increasing average pore diameter.     

Luminescence Behavior of Polynuclear Alkynylcopper(I) Phosphines

A series of soluble trinuclear and tetranuclear copper(I) complexes containing ₃-^l acetylides , and have been synthesized and shown to exhibit rich photoluminescent behavior at room temperature. The electrochemistry of the trinuclear Cu(I) acetylide complexes and the excited-state redox properties of have been investigated. The X-ray crystal structures of and have been determined.     

Heuristic lipophilicity potential for computer-aided rational drug design: Optimizations of screening functions and parameters

In this research we test and compare three possible atom-basedscreening functions used in the heuristic molecular lipophilicity potential(HMLP). Screening function 1 is a power distance-dependent function, b , screening function 2is an exponential distance-dependent function, b_iexp( , and screening function 3 is aweighted distance-dependent function, For every screening function, the parameters ( ,d₀, and are optimized using 41 common organic molecules of 4 types of compounds:aliphatic alcohols, aliphatic carboxylic acids, aliphatic amines, andaliphatic alkanes. The results of calculations show that screening function3 cannot give chemically reasonable results, however, both the powerscreening function and the exponential screening function give chemicallysatisfactory results. There are two notable differences between screeningfunctions 1 and 2. First, the exponential screening function has largervalues in the short distance than the power screening function, thereforemore influence from the nearest neighbors is involved using screeningfunction 2 than screening function 1. Second, the power screening functionhas larger values in the long distance than the exponential screeningfunction, therefore screening function 1 is effected by atoms at longdistance more than screening function 2. For screening function 1, thesuitable range of parameter d₀ is 1.5 < d₀ < 3.0, and d₀ = 2.0 is recommended. HMLP developed in this researchprovides a potential tool for computer-aided three-dimensional drugdesign.     

Activation of nitrite ion by biomimetic iron(III) complexes

The rate of reaction of NO ₂ ⁻ ion with various Fe^III porphyrins in the presence of PPh₃ is shown to depend on the redox potential of the Fe^III center. There is a linear relationship between the ease of reduction of the Fe^III to Fe^II and the kinetics for the formation of the Fe^II porphyrin nitrosyl adduct, with concomitant oxidation of PPh₃ to PPh₃O. Cyclic voltammograms show reversible one-electron reductions that can be ascribed to the Fe^III/Fe^II couple ranging from E_1/2 = −343 to −145 mV (versus Ag/AgCl). The order of increasing half-wave reduction potentials for the Fe^III/Fe^II porphyrin redox centers studied is octaethylporphyrin > etioporphyrin I > deuteroporphyrin IX dimethyl ester > protoporphyrin IX dimethyl ester > α,β,γ,δ-tetraphenylporphyrin. This sequence of redox potentials complements the pseudo first-order kinetics ( to m s ⁻¹) for the oxidation of PPh₃ and subsequent Fe^II porphyrin nitrosyl adduct formation. The rates of reaction of biomimetic Fe^III porphyrins with NO ₂ ⁻ ion demonstrate how metal center redox properties are influenced by the surrounding ligand. In this paper we have elucidated a possible mechanistic control for the rate of this reaction.