Preparation, characterization, and catalysis of mecro-catalysts

Because catalysis by metals is a surface phenomenon, many technological catalysts contain small (typically nanometre-sired) supported metal particles with a large fraction of the atoms exposed. Many reactions, such as hydrocarbon hydrogenations, are structure-insensitive, proceeding at approximately the same rates on metal particles of various sizes provided that they are larger than 1 nm and show bulk-like metallic behavior. But the catalytic properties are not known when metal particles become so small that their sizes are indium clusters consisting of several indium atoms. Here the catalytic behavior of precisely defined clusters of just four and six indium atoms on solid supports is shown. It is found that the Ir4 and Ir6 clusters differ in catalytic activity both from each other and from metallic Ir particles.     

Design, Synthesis, and Activities of Novel Derivatives of Isophthalamide and Benzene-1,3-disulfonamide

Introduction Themeritsofantiplatelettherapyforthepreven tionofthrombosisincardiovasculardiseaseareevi dent.Meta analysisresultshaveshownthatsecondary preventionbyantiplateletaggregationagentscanreduce theriskofnonfatalmyocardialinfarction(MI)and strokeby2…     

Chemistry, commentary, and community: discussion of “an examination of the vaporization enthalpies and vapor pressures of pyrazine, pyrimidine, pyridazine, and 1,3,5-triazine” by Lipkind and Chickos

Vaporization enthalpies for the isomeric diazines were discussed within the context of recent measurements and estimation techniques. It is suggested that pyridazine shows enigmatic behavior.

One-Pot Synthesis of 5′-Diaryl Esters and Diamidates of Phosphate,Phosphorothioate, and Phosphoroselenoate Derivatives of AZT and d4T

Modified nucleosides such as 3′-azido-2′,3′-dideoxythymide (AZT) and 2′,3′-dideoxy-2′,3′-didehydrothymide (d4T) are of importance as antiviral agents and in other medicinal applications. Consequently, there is interest in new analogs of these compounds and in new methods for preparing them. In this article, a simple but efficient, one-pot synthesis of 5′-diaryl esters and diamidates of phosphate, phosphorothioate, and phosphoroselenoate derivatives of AZT and d4T is described. The reaction of AZT/d4T with phosphorus trichloride, followed with phenols, aniline, or amino acid methyl esters in the presence of a base, led to the corresponding tricoordinated phosphite compounds of AZT/d4T, which were then oxidized with 3-chloroperoxybenzoic acid (m-CPBA), sulfur, or selenium powder to finally afford the corresponding target compounds in good yield.     

γ- and UV-radiation-induced degradation of sphingomyelin,lysosphingomyelin, and related compounds

The experimental data on the formation of final products in the radiolysis of 2-aminoglycerol and lysosphingomyelin (sphingosine phosphocholine) and in the photolysis of N-(2-hydroxypropyl)hexanamide and sphingomyelin suggest the occurrence of the radiation-induced degradation of the above substances with C-C bond cleavage. It was hypothesized that this process occurs by the formation and subsequent degradation of the N-centered radicals of the substrates.     

Theoretical study of spectroscopy,interaction, and dissociation of linear and T-shaped isomers of RgClF (Rg = He,Ne, and Ar) van der Waals complexes

Spectroscopy, interaction energy, and dissociation of linear and T-shaped isomers of HeClF, NeClF, and ArClF van der Waals complexes in their ground state have been studied in detail using MP2 and CCSD(T) methods in conjunction with correlation consistent valence triple and quadruple zeta basis sets. A method, called potential method, has been developed to remove the discrepancy between theoretical and experimental values for the depth of the potential well and dissociation energies for these complexes. This is also supported by the supermolecular approach. Most of the structural and spectroscopic properties of these complexes are first reported and the rest agree very well with the experimental and theoretical values wherever available. Two local minima corresponding to linear and asymmetric T-shaped are found for RgClF complexes. For NeClF complex, the predicted values for the equilibrium bond length and well depth are R _NeCl = 3.096 Å and \( D_{\text{e}}^{\text{p}} \) = 161.50 cm^?1 for the linear isomer and R _NeCl = 3.503 Å and \( D_{\text{e}}^{\text{p}} \) = 126.10 cm^?1 for the T-shaped isomer. Various dissociation channels are also investigated in detail.     

Optical Separation of Racemic Phenyl-alanine, and Structure of Complex Consisting of R-Phenylalanine and R-Mandelic Acid

1INTRODUCTIONTheformationofco-crystalsofadiastereo-mericmolecularcomplexisaneffectivemethodforseparatingracemicmixtureintoitsenantiomers[1,2].Asasequeltotheinvestigationonseparatingtheracemicmandelicacidbyachiralalanineinthelaboratory[3],inthepresentworkt…     

Surface Tension,Activity of Counterion,and Conductivity of the Quaternary System Dodecyldimethylamine Oxide,TX‐100, HCl,and Water

We have investigated the mixing behavior of the mixtures of dodecyldimethylamine oxide (DDAO) and Triton X‐100 (TX‐100) at different ratios of the two surfactants and at different values of pH. From the equilibrium surface tension measurements, the critical micelle concentration (CMC) and surface tensions at CMC data were obtained as functions of the composition. For the binary mixtures of dodecyldimethylamine oxide and TX‐100 at different ratios in the natural values of pH, the behaviors of the mixtures deviate positively from ideal during micellization. The minimum of CMC of the mixtures of dodecyldimethylamine oxide and Triton X‐100 was observed in the range 4.0?) increased with the decrease of pH. At pH=4.99, the activities of the counterion decreased with the increase of the concentration of TX‐100 at a constant concentration of DDAO. At pH=1.96, the activities of the counterion increased with the increase of the concentration of TX‐100. However, the conductivities of the solution decreased with the increase of the concentration of TX‐100 at both pH=4.99 and pH=1.96. The experimental results show that the effect of TX‐100 on the activities of the counterion at pH=4.99 is different from that at pH=1.96.     

Coupled cluster,MP2, and DFT study of structures,stabilities, vibrations,and bonding properties of XXeOH (X = F,Cl, Br,and I)

The optimized geometries, molecular properties, and stabilities of new noble gas molecules, XXeOH (X = F, Cl, Br, and I), were studied using CCSD, MP2, CAM-B3LYP, and WB97XD methods and large basis sets. All XXeOH molecules showed equilibrium structures with Cs symmetry. The results also showed that some bonds in XXeOH could be presented as a typical ionic bond. An alteration in ion-pair character was observed for IXeOH, showing two OH ^? and IXe ⁺ parts, while in other molecules, they could be presented as XeOH ⁺ and X ^? . Two decomposition routes were proposed for these molecules that showed high exothermic reactions. However, despite their low thermodynamic stabilities, their decomposition rate constants were small and all molecules (except BrXeOH) had high kinetic stabilities, indicating the possibility for identification and characterization of these molecules. However, in addition to the calculation of their vibrational frequencies, NBO atomic charges, and hybridizations, the bonding properties of XXeOH molecules were studied by AIM calculations (to calculate electron densities, bond elipticities, and Laplacian of electron densities) and second-order intramolecular perturbation energies using NBO calculations. Moreover, the ease of formations and relative stabilities of XXeOH molecules were compared using heats of formations, Gibbs free energies of formations and isodesmic reactions. These calculations showed that the stability of XXeOH molecules was decreased from F to I.     

Formation,Phase, and Elemental Composition of Micro- and Nano-Dimensional Particles of the Fe–Ti System

X-ray fluorescence, X-ray phase analysis, and transmission Mössbauer and NGR spectrometry are used to study the formation, phase, and elemental composition of Fe–Ti particles. The interaction between Fe(III) ions and dispersed titanium in an aqueous solution containing chloride ions and HF is studied. It is shown that the resulting Fe–Ti samples are a set of core–shell microparticles with titanium cores coated with micro- and nanosized α-Fe nucleation centers with the thinness outer layer of iron(III) oxide characterized by a developed surface.     

Langmuir-Shäfer transfer of fullerenes and porphyrins: formation, deposition, and application of versatile films

Thin films consisting of a fulleropyrrolidine derivative 1 and a novel water-soluble porphyrin 2 were prepared by the Langmuir-Sh?fer (LS, horizontal lifting) method. In particular, a solution of 1 in chloroform and dimethyl sulfoxide was spread on the water surface, while porphyrin 2 (bearing peripheral anionic groups) was dissolved into the aqueous subphase. To the best of our knowledge, such a versatile method of film fabrication for fullerene/porphyrin mixed composite films has never been used before. Evidence of the effective interactions between the two moieties at the air-water interface was obtained from the analysis of the floating layers by means of surface pressure versus area per molecule Langmuir curves, Brewster angle microscopy and UV-visible reflection spectroscopy. The characterisation of the LS films by UV-visible spectroscopy reveals that the two constituents behave as discrete and weakly interacting pi systems. The use of polarised light suggests the existence of a preferential direction of the macrocyclic rings with an edge-on arrangement with respect to the substrate surface. Finally, photoaction spectra were recorded from films deposited by only one horizontal lifting onto indium-tin-oxide (ITO) electrodes and the observed photocurrent increased notably with increasing transfer surface pressure.     

Design, Synthesis and Investigation of Bone Affinity of the Conjugates of 5-Fluorouracil and Hydroxybisphosphonate

Bone tumor, as a common disease, is treated by surgical resection, radiotherapy and chemotherapy. Chemotherapy is one of the most important treatment, however, a major problem of chemotherapy is lack of selectivity of cytotoxic drugs. Although many attempts have been made to increase the selectivity of therapeutic drugs for the bone diseases, such as osteoporosis, paget’s, hypercalcemia and bone metastases by conjugating them with targeting carriers1-4, there are still no bone-targeting agent…     

Synthesis and α-glucosidase inhibitory activity of chrysin,diosmetin, apigenin,and luteolin derivatives

Several derivatives have been synthesized from chrysin, diosmetin, apigenin, and luteolin, which were isolated from diverse natural plants. The α-glucosidase inhibitory activity of these compounds was evaluated. The glucosidase inhibitory activity of all derivatives （IC50 〈 24.396 μmol]L） was higher compared with that of the reference drug, acarbose （IC50=563.601 ±40.492μmol/L）, and 1- deoxynojirimycin （IC50 = 226.912± 12.573 μmol/L）. O3＇,O7-Hexyl diosmetin （IC50 = 2.406 ± 0.101μmol/L） was the most potent inhibitor identified. These compounds showed a higher inhibitory ability compared with their precursors except the luteolin derivatives. In general, the inhibitory activity of the synthetic derivatives was enhanced with long alkyl chains at positions 3＇, 4＇ and 7 of the flavonoid.     

Preparation, Characterization, and Catalytical Application of MgCoAl-Hydrotalcite-Like Compounds

MgCoAl-hydrotalcite-like compounds(MgCoAl-HTLcs)were synthesized using the copre- cipitation method of variable pH values.The effect of each factor on the preparation of HTLcs was discussed systematically,which included pH values,mole ratios of Mg~(2 )to Co~(2 ),the concentrations of the solution,and the temperature and time of the hydrothermal treatment.Besides.the thermal de- composition of MgCoAl-HTLcs was discussed.X-ray diffraction,thermogravimetric analysis,and FT-IR spectroscopy were performed to characterize the MgCoAl-HTLcs samples.The results showed that when the pH=7.6-8.5 or 5.5-6.2,atomic ratios of(Mg~(2 ) Co~(2 ))/Al~(3 )=2 and Mg~(2 )/Co~(2 )ranging from 1.00 to 2.00,temperature and time of hydrothermal treatment being 110℃and 6 h,unique MgCoAl-HTLcs with high crystallinity could be obtained.When the calcination temperature was up to 250℃,the MgO phase was detected coexisting with Al_2O_3 and MgAl_2O_4 was highly spreaded on the derived mixed oxides. The synthesis reaction of benzoin methyl ether with methanol and benzaldehyde was chosen to study the catalytic activity of MgCoAl-HTLcs.The catalyst showed high activity and high stability in the synthesis of benzoin methyl ether in the feasible condition.     

Synthesis,Characterization, and Structures of α-Substituted Selenenyl-Acetophenones

Abstract

A series of α-substituted selenenyl acetophenone derivatives of the types, [PhC(OCH₂CH₂O)CH₂Se]₂, [PhC(OCH₂CH₂O)CH₂SeR], (PhCOCH₂Se)_2, and [PhCOCH₂SeR] have been prepared. These compounds have been characterized by elemental analyses, IR and NMR (¹H, ¹³C, ⁷⁷Se) spectroscopy. The compounds, [PhC(OCH₂CH₂)CH₂Se]₂ and (PhCOCH₂Se)₂ have been structurally characterized by single crystal X-ray diffraction analyses. The former shows intra-molecular Se‐?‐?‐O interaction, while the latter exhibits inter-molecular nonbonding Se‐?‐?‐O interaction.

[Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional text and figures.]     

σ-Alane complexes of chromium, tungsten, and manganese

Photolytic ligand displacement and salt metathesis routes have been exploited to give access to κ(1) σ-alane complexes featuring Al-H bonds bound to [W(CO)(5)] and [Cp'Mn(CO)(2)] fragments, together with a related κ(2) complex of [Cr(CO)(4)]. Spectroscopic, crystallographic, and quantum chemical studies are consistent with the alane ligands acting predominantly as σ-donors, with the resulting binding energies calculated to be marginally greater than those found for related dihydrogen complexes.     

Synthesis, spectroscopic properties, and tautomerism of mono-meso-substituted octamethylporphyrins

The synthesis spectroscopic properties and tautomerism of four novel mono-meso substituted(R)-octamethylporphyrins (R=o-hydroxybenzyl, p-aminobenzyl, 4-pyridinyl, and ferro-cenyl) were investigated. It was found that the porphyrins 2, 3 could be directly prepared in good yields via the coupling reaction of salicylaldehyde and p-aminobenzyl aldehyde with octamethyl-l',8'-dideoxy-ac-biladiene dihydrobromide, respectively. The free energy of activation (G) of the tautomerism of the porphyrins was calculated and interpreted in terms of electronic and steric nature. In contrast with 2-substituted-5,10,15,20-tetraphenylporphyrins, the substituents in meso position do not change the relative amount of two tautomers a and 6.     

Theoretical investigation of the nature and strength of simultaneous interactions of π–π stacking and halogen bond including NMR,SAPT, AIM and NBO analysis

Ab initio MP2/aug-cc-pVDZ calculations were performed to investigate mutual effect between π–π stacking and halogen bond interactions in X-ben||pyr···Cl–F complexes (X = CN, F, Cl, Br, CH₃, OH and H where || and ··· denote π–π stacking and halogen bonds). The results indicate the cooperativity of π–π stacking and halogen bonds in these complexes. This effect was discussed in terms of the energetic, geometrical parameters and charge-transfer properties of the complexes. To explore on the two-bonded spin–spin coupling constant ^2X J(N–F) across ¹⁵N···³⁵Cl–¹⁹F halogen bond in X-ben||pyr···Cl–F complexes, NMR calculations were performed at PBE0/aug-cc-pVDZ levels of theory. To get more insight into the physical nature of the binding energies, Symmetry Adapted Perturbation Theory calculations were carried out. Energy decomposition indicates that the percentage of the electrostatic term in the halogen bonding system constitutes approximately half of the total attractive binding energies, while the percentage of the dispersion term in the π–π stacking complexes constitutes approximately half of the attractive binding energies. In addition, atoms in molecules, natural bond orbital and molecular electrostatic potential were also used to probe the π–π stacking interactions and halogen bonding strengths.