Synthesis and thermal behavior of new ambazone complexes with some transitional cations

Ambazone is a pharmaceutical compound that possesses antiseptic activity and tested as well for anti-tumor properties. Metal complexes of Zn(II), Fe(III), and Cu(II) containing ambazone as ligand were synthesized using a molar ratio salt:ligand of 1:1, heating the mixture up to 50 °C for 6 h. Coordination compounds were characterized by thin-layer chromatography, FT-IR spectroscopy, elemental analysis, and thermal behavior. The non-isothermal experiments were carried out in order to investigate the thermal degradation process of these complexes and were performed in a dynamic air atmosphere at a heating rate β = 10 °C min^?1 from ambient temperature, up to 500 °C. It was revealed that decomposition process is a multistadial one.     

Calcichrome: a re-examination of its structure and chemical properties by solid- and liquid-state NMR,infrared spectroscopy,and selective chemical degradation

Nuclear magnetic resonance and infrared spectroscopies were used to unravel the controversies regarding the structures of calcichrome and calcion. Together with the identification of the products from selective chemical cleavage reactions, these data indicate that structures of both compounds are equivalent with a molecular formula of C₂₀H₁₄N₂O₁₅S₄·3H₂O (2,8,8′-trihydroxy-1,1′-azonaphthelene-3,6,3′,6′-tetrasulfonic acid). The compound has two titratable phenolic protons in aqueous solution with pK_a values of 7.19 ± 0.05 and 11.63 ± 0.05 at 25 ° C. As a ligand, the compound forms a colored complex with calcium(II) at a 1:1 stoichiometric ratio (pH 12.3) with a formation constant of 8.0 × 10³ at 25 ° C. The free form of the ligand at pH 12.3 has a molar maximum molar absorptivity of 1.44 × 10⁴ l mol^?1 cm^?1 at 599 nm, whereas the complexed form has a maximum molar absorptivity of 1.37 × 10⁴ l mol^? cm^?1 at 522 nm.     

Highly active zirconium(IV) catalyst containing sterically hindered hydridotris(pyrazolyl)borate ligand for the polymerization of ethylene

The synthesis and characterization of the novel zirconium (IV) tris(pyrazolyl)borate compound {Tp^Ms*}ZrCl₃ ( 1 ) (Tp^Ms* = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)), as well as its performance in polymerizing ethylene are described. The reaction of ZrCl₄ with 1 equivalent of TlTp^Ms* in toluene at room temperature affords 1 as a white solid in 62% yield. Compound 1 in the presence of MAO showed remarkable productivity using a low Al : Zr molar ratio (6.79×10⁴ kg of PE/(mol Zr·h·[C₂H₄]); toluene, 60°C, Al/Zr = 100). Under identical polymerization conditions, compound 1 and Cp₂ZrCl₂ showed comparable productivities. Compound 1 displayed similar productivities at temperatures in the range of 0–75°C and noticeable productivity at 105°C. The viscosity‐average molecular weight of the polyethylenes depends on the Al : Zr molar ratio and polymerization temperature and varied between 1.09 and 8.98×10⁵ g·mol^–1.     

β‐Cyclodextrin hydrogel incorporating hydrophobically modified poly(N‐isopropylacrylamide) for a temperature‐dependent release

Hydrogels exhibiting a temperature‐dependent release were prepared by incorporating hydrophobically modified poly(N‐isopropylacrylamide) (HmPNIPAM) into β‐cyclodextrin hydrogels (β‐CD hydrogels). The specific loading of HmPNIPAM was about 0.0069 g HmPNIPAM/g β‐CD hydrogels. The incorporation of the polymer was qualitatively conformed by FT‐IR spectroscopy and SEM. The percent release of blue dextran in 24 hr at 20°C (about 77%) was markedly higher than those obtained at 35°C and 45°C (about 53 and 55%, respectively). At the higher temperatures, the volume of the hydrogel could decrease upon the thermal contraction of HmPNIPAM, leading to a smaller mesh and a suppressed release. In fact, the swelling ratio in 24 hr at 35°C and 45°C (about 396% and 405%, respectively) was obviously lower than that obtained at 20°C (about 465%). Copyright © 2011 John Wiley & Sons, Ltd.     

Determination of the inclusion complex constant between oleuropein and cyclodextrins by complexation theory

Oleuropein (OLE) is a major phenolic compound of olive leaf (Olea europaea) and has many therapeutic properties associated with olive leaf extracts. This work concerns the determination of the inclusion complex constant between OLE and cyclodextrins (CDs), based on the competition of two guests for the CD cavity, one being a dye and the other OLE. The dye used was methylorange (MO) and pH 3 was selected, since MO molar absorptivity at 500 nm is at maximum in this condition. A solution of MO, OLE, and α-CD or β-CD, with citrate buffer was used for determining the absorbance values. From these data and by appropriate mathematical modeling, the equilibrium constant for the formation of OLE:CD complexes were obtained: for OLE:α-CD K = 1,352.4 L mol^?1 (R ² = 0.9975) and for OLE:β-CD K = 1,827.9 L mol^?1 (R ² = 0.9991). The results show that OLE has a greater affinity for β-CD than for α-CD and given the relatively high constants, OLE:CD complexes have potential for giving longer shelf lives for OLE medicinal and food additive preparations.     

The crystal and molecular structure of DI-trans-β-styrylmercury

The structure of di-trans-β-styrylmercury has been determined by single crystal X-ray methods from counter data. The compound crystallizes in the orthorhombic space group Pbcn with unit cell dimensions a 15.413(6), b 11.161(9), c 7.668(5) Å, V 1319(1) ų, D_calc 2.049 g/cm³, and Z = 4. The crystal was solved by conventional heavy atom techniques. The crystal consists of individual molecular units with the mercury atom located on a two fold axis of symmetry. The CHgC fragment is nearly linear with an angle of 178°. The β-styryl groups are oriented so that a dihedral angle of 66.8° is formed between the planes defined by HgC(1)C(2) and HgC(1)′C(2)′ fragments. The HgC bond distance is 2.07(4) Å.     

Synthesis and structure of triphenylantimony diphthalate

Triphenylantimony diphthalate hydrate (I) has been synthesized by the reaction between triphenylantimony and ortho-phthalic acid in the presence of hydrogen peroxide (molar ratio, 1: 2: 1). According to X-ray diffraction data, the antimony atom in a symmetric molecule of compound I (the SbC₃O₂ coordinating moiety has point group C _2v ) has a trigonal bipyramidal coordination. The OSbO axial angle and the CSbC angles in the equatorial plane are 179.83(12)° and 106.04(9)°, 147.93(18)°, respectively. The bond length are 2.153(2) (Sb-O), and 2.110(4), 2.120(3) Å (Sb-C). Intramolecular Sb…O=C contacts (2.802(3) Å) take place in compound I.     

Temperature-dependent selectivity of inclusion by <Emphasis Type="Italic">trans</Emphasis>-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid

From acetophenone solution with a small amount of water, a widely used clathrate forming compound, trans-9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboxylic acid (DED), crystallizes either in the form of a clathrate with acetophenone (25°C) or in the form of hydrate (5°C). The clathrate of DED with acetophenone is triclinic, space group P-1 with the unit cell parameters: a = 8.5002(2) Å, b = 12.5247(8) Å, c = 12.8251(8) Å; α = 62.876(2)°, β = 80.454(2)°, γ = 89.789(2)°; V = 1194.4(1) ų, Z = 2; the molar ratio DED:acetophenone is 2:3. The clathrate is of channel type; the system of mutually intersecting channels propagates in [100] and [01–1] directions in the structure. The guest molecules of acetophenone are included in the channels and do not form any H-bonds with the host molecules of DED. The hydrate of DED crystallizes in monoclinic system, in space group C2/c, with the unit cell parameters: a = 31.770(6) Å, b = 8.503(2) Å, c = 12.888(3) Å; β = 104.26(3)°; V = 3374(1) ų, Z = 8; the molar ratio DED:water is 1:3. One of two carboxylic groups of the molecule of DED is deprotonated and the proton is incorporated into the hydroxonium ion H₃O⁺. The crystal structure of the hydrate of DED is of layer type with well distinguished hydrophobic and hydrophilic parts.     

The promoting effect of chelating ligands in the oxidative carbonylation of phenol to diphenyl carbonate catalyzed by Pd–Co–benzoquinone system

The system Pd(OAc)₂/BQ/Co(acac)₃ (BQ=benzoquinone), in combination with tetrabutylammonium bromide (TBAB) as a surfactant agent and a chelating ligand such as 2,9-dimethyl-1,10-phenanthroline (dmphen) or 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (dmdpphen), is an efficient catalyst for the oxidative carbonylation of phenol to diphenyl carbonate (DPC). The best results have been obtained using the system Pd(OAc)₂/BQ/Co(acac)₃/dmphen=1/30/8/5 (molar ratio) in which [Pd]=10⁻³ mol l⁻¹ and TBAB/Pd=60/1. This system gives the maximum productivity of 700 mol DPC/mol Pd h at 135°C and under P_tot=60 atm (CO/O₂=10/1 molar ratio). The role of each component of the catalytic system is discussed and a catalytic cycle is proposed.     

ChemInform Abstract: Synthesis,Structure, and Electronic Structure of CsAgGa2Se4.

The new title compound is prepared from a mixture of AgGaSe₂ (obtained from the elements at 900 °C, 2 d) and CsI in the molar ratio 1:2 (silica tube, Ar, 800 °C, 48 h).     

Controlled radical polymerization of styrene mediated by the C‐phenyl‐N‐tert‐butylnitrone/AIBN pair: Kinetics and electron spin resonance analysis

Kinetics of the free radical polymerization of styrene at 110 °C has been investigated in the presence of C‐phenyl‐N‐tert‐butylnitrone (PBN) and 2,2′‐azobis(isobutyronitrile) (AIBN) after prereaction in toluene at 85 °C. The effect of the prereaction time and the PBN/AIBN molar ratio on the in situ formation of nitroxides and alkoxyamines (at 85 °C), and ultimately on the control of the styrene polymerization at 110 °C, has been investigated. As a rule, the styrene radical polymerization is controlled, and the mechanism is one of the classical nitroxide‐mediated polymerization. Only one type of nitroxide (low‐molecular‐mass nitroxide) is formed whatever the prereaction conditions at 85 °C, and the equilibrium constant (K) between active and dormant species is 8.7 × 10^?10 mol L^?1 at 110 °C. At this temperature, the dissociation rate constant (k_d) is 3.7 × 10^?3 s^?1, the recombination rate constant (k_c) is 4.3 × 10⁶ L mol^?1 s^?1, whereas the activation energy (E_a,diss.), for the dissociation of the alkoxyamine at the chain‐end is ～125 kJ mol^?1. Importantly, the propagation rate at 110 °C, which does not change significantly with the prereaction time and the PBN/AIBN molar ratio at 85 °C, is higher than that for the thermal polymerization at 110 °C. This propagation rate directly depends on the equilibrium constant K and on the alkoxyamine and nitroxide concentrations, as well. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1219–1235, 2007     

Unsaturated dodecahedranes—Synthesis of the highly pyramidalized,highly reactive C20H18 and C20H16 olefins

Methodological alternatives for the preparation of highly strained, highly pyramidalized dodecahedrene 2 (E_str=87.3 kcal mol^?1; ?=43.5°, MM2) and 1,16-dodecahedradiene 3 (E_str=105.3 kcal mol^?1; ?=42.9°, MM2) have been explored, protection/deprotection strategies have been tested—with the eye on their utilization for the generation of higher unsaturated dodecahedranes (e.g. 1,4, 16-triene 4, 1,4,10 (14),16-tetraene 5). For the acquisition of preparative quantities of monoene 2 the “P₂F” catalyzed cis-β-elimination in bromododecahedrane, of diene 3 the FVP fragmentation of a “twofold protected” precursor (bis-furan adduct) have become the protocols of choice, which both profit from the recent synthetic advances along the pagodane → dodecahedrane scheme. Because of unusually effective steric protection the highly tilted C=C double bonds of 2 (λ_max (CH₃CN) = 254 nm, ν _C=C = 1658 cm^?1, δ_C=C = 164.4) and 3 (δ_C=C = 170.5) enter into thermal stabilization pathways (dimerization, oligomerization) only at higher temperatures (for 2 ca. 50% consumption after 5 h at 100°C in a 3·10^?3 molar toluene solution); extreme sensitivity to oxygen is primarily attributed to kinetically and thermodynamically promoted allylic hydrogen abstraction.     

Structure-activity correlations of calcined Mg-Al hydrocalcites for aliphatic polycarbonate synthesis <Emphasis Type="Italic">via</Emphasis> transesterification process

Mg-Al mixed oxides with different Mg/Al molar ratio were prepared by thermal decomposition of hydrotalcitelike precursors at 500 °C for 5.0 h and used as catalysts for the transesterification of diphenyl carbonate with 1,4-butanediol to synthesize high-molecular-weight poly(butylene carbonate) (PBC). The structure-activity correlations of these catalysts in this transesterification process were discussed by means of various characterization techniques. It was found that the chain growth for the formation of PBC can only be obtained through connecting ―OH and ―OC(C)OC₆H₅ end-group upon removing the generated phenol, and the sample with Mg/Al molar ratio of 4.0 exhibited the best catalytic performance, giving PBC with M _w of 1.64 × 10⁵ g/mol at 210 °C for 3.0 h. This excellent activity depended mainly on the specific surface area and basicity rather than pore structure or crystallite size of MgO.     

NaTe3: eine Verbindung mit verbrückten Te126−-Clustern

NaTe₃ – a Compound with Cuban-like Clusters Te₁₂^6? NaTe₃ results as a greyish microcrystalline powder if stoichiometric amounts of the pure elements sodium and tellurium (molar ratio 1:3) are allowed to react in liquid ammonia at about ?50°C. After melting the crude product (500°C, 1 h, corundum crucible in sealed glass ampoule), followed by an annealing period (380°C, 5 days) NaTe₃ yields as a silvery compound with metallic lustre. NaTe₃ is trigonal, space group P3 c1, Z = 12, with a = 9.033(2) Å and c = 21.930(4) Å. It contains Te₆^2?-chains, linked together via their terminal atoms producing infinite strings. These strings may be thought to be built up of cuban-like clusters Te₁₂^6?.     

Biochemical properties and cyclodextrin production profiles of isoforms of cyclodextrin glycosyltransferase

Cyclodextrin glycosyltransferase (CGTase) catalyzes the conversion of starch to cyclodextrin (CD), an important host molecule for the study of host?Cguest interactions. CGTase from Paenibacillus sp. RB01 and its recombinant form showed the same isoform pattern. The three isoforms, two major (isoforms I and II) and one minor (isoform III), all had a different net charge but the same molecular mass. The aim of this work was to characterize the three isoforms, and especially to compare their CD production profiles. Isoforms I and II were separated on a FPLC Mono Q column and showed the same optimum pH (pH 5 for dextrinizing and pH 6?C7 for cyclization activity) and optimum temperature (65?C70 °C for both activities). However, the two isoforms differed in their catalytic efficiency of the coupling reaction with variable concentrations of the ??-CD donor in the presence of a fixed amount of cellobiose acceptor, with k_cat/K_m values of 3.46 × 10^?3 and 2.20 × 10^?3 mM^?1 min^?1, for isoforms I and II, respectively. Both isoforms I and II were found to have ??-CGTase activity and gave a similar CD6:CD7:CD8 product ratio of 0.2:1.0:0.6, with an increase in the ratio of the small-ring to the large-ring CDs from 1.0:0.5 to 1.0:0.3 from a 6 to 24 h reaction time. However, in terms of maximal CD yields, the two isoforms differed in their optimal reaction temperature and time required, the optimal conditions being at 40 °C for 6 h for isoform I and at 60 °C for 24 h for isoform II.     

Synthesis, structural elucidation and X-ray analysis of triphenyltin(IV) [2-(2,3-dimethylanilino)nicotinate]

Triphenyltin(IV) [2-(2,3-dimethylanilino)nicotinate] was prepared by the interaction of triphenyltin(IV) hydroxide and 2-(2,3-dimethylanilino)nicotinic acid in 1:1 ratio. This compound was characterized by elemental analyses, IR, multinuclear NMR spectroscopy (¹H and ¹³C) and mass spectrometry. The structure of title compound was confirmed by single crystal X-ray crystallography. The coordination around the tin atom was studied both in solution and solid state. The geometry around tin is trigonal bipyramidal in solid state while it is tetrahedral in solution. The compound belongs to Monoclinic system, having space group P 21/c with unit cell dimensions a = 17.002(8) Å, b = 9.0793(3) Å, c = 18.2616(9) Å, α = 90 (°) β = 107.381(4) (°), γ = 90 (°).     

Synthesis,characterization, and crystal structure of modified benzophenone UV-absorber containing reactive group

A modified benzophenone UV-absorber containing reactive group (4-(4,6-dichloro-1,3,5-triazin-2-yloxy)-2-hydroxyphenyl)phenyl)methanone (UV-DTHM) has been prepared in good yield from the nucleophilic substitution reaction of 2,4-dihydroxy benzophenone with 2,4,6-trichlorotriazine, catalyzed by 1.3 equiv. NaOH. The most favorable reaction conditions (the catalyst dosage, the mole ratio of the reactants, and reactive time) were selected. The compound was characterized by IR spectroscopy, ¹H NMR, ¹³C NMR, mass spectrometry, elemental analysis, and single crystal X-ray diffraction. The crystal monoclinic, space group C c with the unit cell parameters a = 3.987(2), b = 30.688(16), c = 12.423(6) Å and α = 90.00, β = 92.117(15), γ = 90.00º, Z = 4, R = 0.0620. wR(F ²) = 0.1589. The crystal structure reveals that 2,4,6-trichlorotriazine is boned to 4-seat hydroxyl of 2,4-dihydroxy benzophenone and a intramolecular hydrogen bond is formed with hydrogen of 2-hydroxyl and oxygen of carbonyl group. Moreover, thermogravimetric analysis (TGA) of UV-DTHM was studied, showing two distinct endothermic peaks at temperatures of 281.5 and 358.5 °C. The molar absorption coefficient of UV-DTHM is 1.6 × 10⁴ and 6.3 × 10³ at 268 and 330 nm, respectively, and shows excellent ultraviolet absorption property.     

Effect of Temperature on the Encapsulation of the Drug Tetracaine Hydrochloride by β-Cyclodextrin and Hydoxypropyl-β-Cyclodextrin in Aqueous Medium

The encapsulation of tetracaine hydrochloride (TTAC...HCl) by β-cyclodextrin (β-CD) andhydroxypropyl-β-cyclodextrin (HPBCD) has been analyzedfrom a thermodynamic point of view, by means of conductometric studies at different temperatures. Conductivity measurements of aqueous solutions of the drug were performed: (i) in the absence of CD, as a function of drug concentration; and (ii) in the presence of CD, as a function of CD concentration, both studies at different temperatures ranging from 15 to 40 °C. The stoichiometry of the complexes, the association constants, and the ionic molar conductivities at infinite dilution ofthe free (λ_DRUG ⁰) and complexed(λ_CD:DRUG ⁰) drug were obtained from these conductivitydata. From the dependency of the association constants with temperature (van't Hoff analysis), the inclusion complexes formed by β-CD and/or HPBCD and the drug were found to be enthalpy driven, with a favorable enthalpic term dominant over an unfavorable entropic term. This pattern could be revealing the contribution of van der Waals interactions, hydrophobic effect and solvent reorganization as the main driven forces promoting the interaction.     

Hydrogen bond studies: Part 118. A deuteron magnetic resonance study of BeSO4· 4D2O and Li2SO4· D2O

The electric field gradient (EFG) tensors at the deuterons in the water molecules in BeSO₄ · 4D₂O at 25°C are reported. The quadrupole coupling constants (e²Q/h) and asymmetry parameters (η) for the two independent deuterons are 181.1(4) and 194.8(3) kHz, and 0.226(4) and 0.123(3), respectively. The EFG tensor corresponding to the smallest e²qQ/h is considerably distorted by the beryllium ion, which causes a high η value as well as a deviation of the y-principal axis by 21.8(6)° from the normal to the water molecule plane. A redetermination of the EFG tensors at the deuterons in the water molecule in Li₂SO₄ · D₂O at 25°C and ?110°C is also reported. The e²Q/h and η values for the two deuterons are 236.6(1.2) and 239.8(1.1) kHz, and 0.091(8) and 0.126(7), respectively, at ?110°C. The corresponding e²qQ/h and η values for the averaged EFG tensor at 25°C are 125.8(1.1) kHz and 0.813(13), respectively. The results are in good agreement with those from the pioneer work by Ketudat and Pound, 20 years ago on the same compound.     

Thermal stability and structure of a new co-crystal of theophylline formed with phthalic acid

A new co-crystal of theophylline and phthalic acid with 1:1 molar ratio has been prepared. It crystallises in the monoclinic crystal system, space group P2₁/c, a=11.5258(9), b=10.1405(6), c=13.9066(12) Å, β=106.827(4)°. The structure of the co-crystal has been revealed by single crystal X-ray diffraction. An infinite helical polymeric chain is formed by intermolecular hydrogen bonds of the two neutral constituents. The hydroxyl group and carbonyl oxygen atom in one of the carboxyl groups of phthalic acid form hydrogen bonds to O6 and to N(7)H atoms of theophylline, respectively, while the other carboxyl OH group of phthalic acid is in hydrogen bond to N9 atom of theophylline by very strong intermolecular interactions proven by 1883 cm^?1 centred peak in FTIR spectrum.Thermal degradation of this new supramolecular compound is a two-step process in air. At first phthalic acid (47.4%) released up to 230°C, meanwhile it loses water and transforms into phthalic anhydride. In EGA-MS spectra, the characteristic fragments of water (m/z=17, 18) appear from about 180°C, while absorption bands of phthalic anhydride are shown in EGA-FTIR spectrum at about 210°C. In the second step theophylline begins to sublime, melts at 276°C, and then evaporates up to 315°C with minute residues.