Synthesis and characterization of a 2, 5-Bis(trimethylsilyl)-substituted Bis(1, 1′-silolide) dianion

A novel silyl-substituted bis(1, 1′-silolide) dianion has been isolated and characterized by single-crystal X-ray analysis for the first time. The ¹H, ²⁹Si, and ¹³C NMR spectra show significant delocalization of the negative charges to the silole ring. X-ray crystallography revealed equalized C?C distances and DFT calculation also indicates for significant aromaticity. Reaction with trimethylchlorosilane gave the expected bis(1, 2, 5-tris(trimethylsilyl)-3, 4-diphenyl-silacyclopentadienyl).     

H atom adsorption and diffusion on Si(110)-(1×1) and (2×1) surfaces

We present a periodic density-functional study of hydrogen adsorption and diffusion on the Si(110)-(1×1) and (2×1) surfaces, and identify a local reconstruction that stabilizes the clean Si(110)-(1×1) by 0.51 eV. Hydrogen saturates the dangling bonds of surface Si atoms on both reconstructions and the different structures can be identified from their simulated scanning tunneling microscopy/current image tunneling spectroscopy (STM/CITS) images. Hydrogen diffusion on both reconstructions will proceed preferentially along zigzag rows, in between two adjacent rows. The mobility of the hydrogen atom is higher on the (2×1) reconstruction. Diffusion of a hydrogen vacancy on a monohydride Si(110) surface will proceed along one zigzag row and is slightly more difficult (0.2 eV and 0.6 eV on (1×1) and (2×1), respectively) than hydrogen atom diffusion on the clean surface.     

Syntheses and Magnetism of μ-1, 3, 5-Benzenetricarboxylato Trinuclear Manganese(Ⅱ) and Nickel(Ⅱ)Complexes

IntroductionThestudyofmagneticexchangeinteractionbetweenparamagneticcenterspropagatedbymulti-atombridgesisofcurrentinterestduetounderstandingthepathwayofelectrontransferinbio1ogicalsystemandobtainingsomeusefulin-formationaboutdesigningmolecule-basedmagnets.Manypapers['-'Jdealingwithphthalato,isophthalatoandterephthalatoligandsasamulti-atombridgeshavebeenpublished.1thasbeenrevealedbythevariable-temperaturemagneticsusceptibilityinvestigationthatlong-rangemagneticcouplingoccursbetweentwoparamagne…     

Synthesis and cytotoxicity of dinuclear platinum(Ⅱ) complexes of (1S, 3S)-1, 2, 3, 4-tetrahydroisoquinolines

A series of novel dinuclear platinum(Ⅱ) complexes with (1S, 3S)-1,2,3,4-tetrahydroisoquinolines as the ligands were synthesized as potential anticancer agents in several steps starting from commercially available L-DOPA. The cytotoxicities of the series of dinuclear platinum(Ⅱ) complexes of tetrahydroisoquinoline were tested against HCT-8, BEL-7402, A2780, MCF-7, Hela, A549 and BGC-823 cell lines by the MTT test. These complexes showed selective inhibition activity against cisplatin-insensitive cell line Skov3.     

Density functional study of S(N) 2 substitution reactions for CH(3) Cl + CX(1) X(2•-) (X(1) X(2) = HH, HF, HCl, HBr, HI, FF, ClCl, BrBr, and II)

A systematic investigation on the S_N2 displacement reactions of nine carbene radical anions toward the substrate CH₃Cl has been theoretically carried out using the popular density functional theory functional BHandHLYP level with different basis sets 6‐31+G (d, p)/relativistic effective core potential (RECP), 6‐311++G (d, p)/RECP, and aug‐cc‐pVTZ/RECP. The studied models are CX¹X^2?? + CH₃Cl → X²X¹CH₃C^? + Cl^?, with CX¹X^2?? = CH₂^??, CHF^??, CHCl^??, CHBr^??, CHI^??, CF₂^??, CCl₂^??, CBr₂^??, and CI₂^??. The main results are proposed as follows: (a) Based on natural bond orbital (NBO), proton affinity (PA), and ionization energy (IE) analysis, reactant CH₂^?? should be a strongest base among the anion‐containing species (CX¹X^2??) and so more favorable nucleophile. (b) Regardless of frontside attacking pathway or backside one, the S_N2 reaction starts at an identical precomplex whose formation with no barrier. (c) The back‐S_N2 pathway is much more preferred than the front‐S_N2 one in terms of the energy gaps [ΔE(front)?ΔE(back)], steric demand, NBO population analysis. Thus, the back‐S_N2 reaction was discussed in detail. On the one hand, based on the energy barriers (ΔE and ΔE) analysis, we have strongly affirmed that the stabilization of back attacking transition states (b‐TSs) presents increase in the order: b‐TS‐CI₂ < b‐TS‐CBr₂ < b‐TS‐CCl₂ < b‐TS‐CHI < b‐TS‐CHBr < b‐TS‐CHCl < b‐TS‐CF₂ < b‐TS‐CHF < b‐TS‐CH₂. On the other hand, depended on discussions of the correlations of ΔE with influence factors (PA, IE, bond order, and ΔE), we have explored how and to what extent they affect the reactions. Moreover, we have predicted that the less size of substitution (α‐atom) required for the gas‐phase reaction with α‐nucleophile is related to the α‐effect and estimated that the reaction with the stronger PA nucleophile, holding the lighter substituted atom, corresponds to the greater exothermicity given out from reactants to products. © 2012 Wiley Periodicals, Inc. J Comput Chem, 2012     

Facile Syntheses of (±)-Curcuphenol, (±)-Curcudiol, (±)-Curcuhydroquinone,and (±)-Curcuquinone

The syntheses of (±)-curcuphenol 1, (±)-curcudiol 2, (±)-curcuhydroquinone 3, and (±)-curcuquinone 4 have been achieved. The key steps involved in the syntheses were the Reformatsky reaction and hydrogenation reaction.     

Enzymatic resolution of (±)-cis- and (±)-trans-1-aminoindan-2-ol and (±)-cis- and (±)-trans-2-aminoindan-1-ol

Pseudomonas cepacia lipase (PSL) efficiently catalyses the kinetic resolution of (±)-cis- and (±)-trans-1-aminoindan-2-ol through the O-acylation reaction of the corresponding N-benzyloxycarbonyl derivative using vinyl acetate as the acyl donor. In a similar way, cis-N-Cbz-2-aminoindan-1-ol is resolved when isopropenyl acetate is used as the acylating agent. The enantioselectivity of the reaction was lower for (±)-trans-N-Cbz-2-aminoindan-1-ol due to the different steric requirements for the two conformers of this substrate.     

Electronic structure and UV–Vis spectra simulation of square planar Bis(1-(4-methylphenylazo)-2-naphtol)-Transition metal complexes [M(L)2]x (M = Ni,Pd, Pt,Cu, Ag,and x = − 1, 0, + 1): DFT and TD-DFT study

Structural Chemistry - DFT/B3LYP calculations with full geometry optimizations have been carried out on 1-phenylazo-2-naphthol and their metal complexes of formula M(MePhNap)2 (M?=?Ni,...     

Syntheses,structures, and properties of two metal-organic frameworks comprising bpdc (2,2′-biphenyldicarboxylate) and bipb (2,2′-bis(imidazol-1-ylmethyl)-biphenyl)

Two new coordination polymers, [Cd(bpdc)(bibp)(H₂O)₂] _n (1) and [Zn(bpdc)(bibp)] _n (2), have been hydrothermally synthesized from 2,2′-biphenyldicarboxylate (bpdc) and 2,2′-bis(imidazol-1-ylmethyl)-biphenyl (bipb). Polymer 1 features a 1-D tubelike porous chain along the a direction with coordinated water molecules occupying the pores. The double-chain of polymer 2 possesses alternating rectangular rings [(bpdc)₂Zn₂] and [(bibp)₂Zn₂] with Zn as nodes. The polymers exhibit strong fluorescent emissions in the solid state at room temperature and could be significant as photoactive materials.     

Methylenecyclohexane annulation. Total synthesis of (±)-axamide-1, (±)-axisonitrile-1, and the corresponding C-10 epimers

Conjugate addition of 2-(5-chloro-1-pentenyl)magnesium bromide (12) to 2-methyl-2-cyclopenten-1-one (6), followed by intramolecular alkylation of the resultant product, afforded (85%) the bicyclic ketone 7, which was transformed (77%) into the enone 16. Titanium tetrachloride-catalyzed conjugate addition of 3-methyl-1,1-bis(trimethylsiloxy)-1-butene to 16 gave (93%) a 3:2 mixture of the keto acids 20 and 21, which were separated. Compound 20, the stereochemistry of which was confirmed by a single-crystal X-ray analysis, was converted into (±)-axamide-1 (1) and (±)-axisonitrile-1 (2), while 21 was transformed into the corresponding C-10 epimers 8 and 9, respectively.     

Total synthesis of (±)-maistemonine, (±)-stemonamide, and (±)-isomaistemonine

A full account of the total synthesis of (±)-maistemonine, (±)-stemonamide, and (±)-isomaistemonine is presented. Two approaches have been developed to construct the basic pyrrolo[1,2-a]azepine core of the Stemona alkaloids, featuring a tandem semipinacol/Schmidt rearrangement of a secondary azide and a highly stereoselectively desymmetrizing intramolecular Schmidt reaction, respectively. To build the common spiro-γ-butyrolactone, a new protocol was carried out by utilizing an intramolecular ketone-ester condensation as the key transformation. The vicinal butyrolactone moiety of (±)-maistemonine was stereoselectively introduced via a one-pot procedure involving the epimerization at C-3 and carbonyl allylation/lactonization. Moreover, (±)-stemonamide was divergently synthesized from a common intermediate, and (±)-isomaistemonine was obtained via the epimerization of (±)-maistemonine at C-12.     

Interactions of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1)

The coupled cluster singles and doubles method with perturbative treatment of triple excitations is applied to calculate the potentials of M(z)-X complexes (M = Cu, Ag, and Au; X = He, Ne, and Ar; and z = ±1). The bond functions and the basis set superposition errors are considered to obtain accurate interaction energies. The potential energy curves of all complexes are obtained. The vibrational energy levels and the spectroscopic parameters for these complexes are determined. The analytical potential energy functions are also fitted based on the potential energies.     

Excited-state dynamics of trans,trans-1,3,5,7-octatetraene: estimation of decay rate constants of 1(1)B(u) ⇝ 2(1)A(g) and 2(1)A(g) ⇝ 1(1)A(g) internal conversions

The general expressions we previously derived for calculating internal conversion rate constants between two adiabatic displaced-distorted-rotated potential energy surfaces, by including all vibratinal modes, are applied to estimate the decay rate constants of 1(1)B(u) ? 2(1)A(g) and 2(1)A(g) ? 1(1)A(g) internal conversions in trans,trans-1,3,5,7-octatetraene molecule. The minimal models with respect to the number and types of vibrational modes are determined for these processes. Our calculations show that in the low temperature limit the 1(1)B(u) ? 2(1)A(g) internal conversion takes place on a 232-290 fs time scale in the condensed phase and 2 ps in the gas phase, whereas 2(1)A(g) ? 1(1)A(g) internal conversion takes place on a 2 μs time scale under the isolated conditions.     

Spectroscopic analysis of the coupled 1(1)Π, 2(3)Σ+ (Ω = 0-, 1), and b(3)Π (Ω = 0±, 1, 2) states of the KRb molecule using both ultracold molecules and molecular beam experiments

We report the spectroscopic characterization of excited electronic states of KRb by combining spectra from molecular beam (MB) experiments with those from ultracold molecules (UM) formed by photoassociation (PA) of ultracold atoms. Spectra involving the 1(1)Π, 2(3)Σ(+), and b(3)Π states in a strongly perturbed region have been identified. This approach provides a powerful method to identify the vibrational levels of the excited electronic states perturbed globally by neighboring electronic states. This is because the two sets of spectra from the UM and the MB experiments probe the same energy region from very different initial electronic states. The UM experiments utilize high v' levels of the a(3)Σ(+) state with large internuclear separations, while the MB experiments utilize low v' levels of the ground X(1)Σ(+) state with near-equilibrium internuclear separations. Only the Ω = 1 levels of the 2(3)Σ(+) and b(3)Π states are observed in the MB spectra, while the Ω = 0(-), 1 levels of the 2(3)Σ(+) state and the Ω = 0(±), 1, 2 levels of the b(3)Π state are observed in the UM spectra.     

Formation, structure, and reactivities of 1:1 adducts between quadricyclane and (η-cyclopentadienyl)(1,2-diphenyl- or -dimethoxycarbonyl-1,2-ethenedithiolato)rhodium(III)

The rhodiadithiolene complexes [Rh(Cp)(S₂C₂Z₂)] (Z=Ph (1a) and COOMe (1b)) reacted with quadricyclane (Q) to give 1:1 adducts [Rh(Cp)(S₂C₂Z₂) (C₇H₈)] (Z=Ph (2a) and COOMe (2b)) in which Rh and S of the complexes are bridged by C(7) (bridge carbons) and C(5) (edge carbons) of norbornene (C₇H₈), respectively. The structure of the adduct 2a was re-investigated and determined by X-ray structural analysis. The rhodiadithiolene complexes and those adducts showed the catalytic activities for the thermal isomerization from Q to norbornadiene (NBD). Adduct 2a photochemically dissociated to give the original complex 1a and NBD upon irradiation with a high-pressure mercury lamp. Skeletal rearrangements of the hydrocarbon moiety were confirmed in the formation of these adducts and in their photo-dissociation, according to deuterium labeling experiments.     

Synthesis, Structure and Dielectric Property of Ba_(1- x)Sr_xZr_yTi_(1- y)O_3

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Syntheses,molecular structures,and antiviral activities of 1- and 2-(2′-deoxy-d-ribofuranosyl)cyclohepta[d][1,2,3]triazol-6(1H)-ones and 1-(2′-deoxy-d-ribofuranosyl)cyclohepta[b]pyrrol-8(1H)-one

The synthesis of a novel class of 2′-deoxyribonucleosides possessing tropone-fused nitrogen heterocycles as nucleobases was developed. The reaction of alkali metal salts of 1H-cyclohepta[d][1,2,3]triazol-6-one with 2-deoxy-3,5-di-O-(p-toluoyl)-α-d-ribofuranosyl chloride (α-chlorosugar) afforded an anomeric mixture of N1- and N2-coupled glycosylation products. Good stereospecificity in relation to the amount of the β-anomer was achieved in the less polar solvent DME. The reactions of the sodium salt of 1H-cyclohepta[b]pyrrol-8-one and its 3-methyl derivative with an α-chlorosugar in DME gave the β-anomer of the N1-coupled glycosylation products. The glycosylation products were treated with NaOMe in MeOH to produce the desired 2′-deoxyribonucleosides. X-ray structural analyses of the three nucleosides prepared confirmed their anomeric configuration and revealed that their sugars were puckered. The β-anomers of the nucleosides had weak antiviral activities for herpes simplex virus type 1 and herpes simplex virus type 2 in comparison with those of acyclovir (ACV). These nucleosides showed no cytotoxicity on a lung (A549) and two colon (HT-29 and HCT-116) cancer cell lines.     

Synthesis and Characterization of Nickel(Ⅱ) and Copper(Ⅱ) Complexes with Schiff Base (1R,2R)-(-)-Diaminocyclohexane-N,N'-bis(3-tert-butyl-5-(4'-benzoic acid)-salicylidene)

Two homochiral metallosalen complexes,Ni(salen) (salen=(1R,2R)-(-)-diaminocyclohexane-N,N'-bis(3-tert-butyl-5-(4'-benzoic acid)-salicylidene) 1 and Cu(salen) 2,have been synthesized and characterized by IR,microanalysis,TGA,powder and single-crystal X-ray crystallography. Both 1 and 2 crystallize in orthorhombic space group P2_12_12 with Z=4. For 1,α= 12.082(2),b = 15.447(3),c = 18.784(4)(A),V= 3505.7(12) (A)~3,M_r = 731.50,D_c = 1.386 g/cm~3,μ= 0.606 mm~(-1),F(000)=1544,the final GOOF=1.043,R=0.0496 and wR=0.1248 for 4791 observed reflections with Ⅰ> 2σ(Ⅰ). For 2,α=12.181(2),b=15.501(3),c=18.877(4)(A),V= 3564.3(12)(A)~3,M_r=736.33,Dc = 1.372 g/cm~3,μ=0.665 mm~(-1),F(000)=1548,the final GOOF= 1.062,R=0.0575 and wR=0.1508 for 4562 observed reflections with Ⅰ> 20(Ⅰ). The crystal structures of 1 and 2 are isostructural with very similar supramolecular structures. An infinite two-dimensional network is generated by hydrogen bonding interactions and intermolecular π…π interactions.     

Homoleptic 1-D iron selenolate complexes-synthesis, structure, magnetic and thermal behaviour of (1)(∞)[Fe(SeR)2] (R=Ph, Mes)

The first examples of polymeric homoleptic iron chalcogenolato complexes (1)(∞)[Fe(SePh)(2)] and (1)(∞)[Fe(SeMes)(2)] (Ph = phenyl = C(6)H(5), Mes = mesityl = C(6)H(2)-2,4,6-(CH(3))(3)) have been both prepared by reaction of [Fe(N(SiMe(3))(2))(2)] with two equivalents of HSeR (R = Ph, Mes) while (1)(∞)[Fe(SePh)(2)] was found to be also easily accessible through reactions of either FeCl(2), Fe(OOCCH(3))(2) or FeCl(3) with PhSeSiMe(3) in THF. In the crystal, the two compounds form one-dimensional chains with bridging selenolate ligands comprising distinctly different Fe-Se-Fe bridging angles, namely 71.15-72.57° in (1)(∞)[Fe(SePh)(2)] and 91.80° in (1)(∞)[Fe(SeMes)(2)]. Magnetic measurements supported by DFT calculations reveal that this geometrical change has a pronounced influence on the antiferromagnetic exchange interactions of the unpaired electrons along the chains in the two different compounds with a calculated magnetic exchange coupling constant of J = -137 cm(-1) in (1)(∞)[Fe(SePh)(2)] and J = -20 cm(-1) in (1)(∞)[Fe(SeMes)(2)]. In addition we were able to show that the ring molecule [Fe(SePh)(2)](12) which is a structural isomer of (1)(∞)[Fe(SePh)(2)] behaves magnetically similar to the latter one. Investigations by powder XRD reveal that the ring molecule is only a metastable intermediate which converts in THF completely to form (1)(∞)[Fe(SePh)(2)]. Thermal gravimetric analysis of (1)(∞)[Fe(SePh)(2)] under vacuum conditions shows that the compound is thermally labile and already starts to decompose above 30 °C in a two step process under cleavage of SePh(2) to finally form at 250 °C tetragonal PbO-type FeSe. The reaction of (1)(∞)[Fe(SePh)(2)] with the Lewis base 1,10-phenanthroline yielded, depending on the conditions, the octahedral monomeric complexes [Fe(SePh)(2)(1,10-phen)(2)] and [Fe(1,10-phen)(3)][Fe(SePh)(4)].     

Extraction,Separation and Spectrophotometric Determination of Bismuth(III) Using 1(4′-Bromophenyl) 4,4,6-Trimethyl (1H,4H)-Pyrimidine-2-Thiol

Abstract

The operating conditions for the spectrophotometric determination of bismuth(III) with 1-(4′-bromophenyl)-4,4,6-trimethyl-(1H,4H)-pyrimidine-2-thiol (4′bromo PTPT) as a ligand by a liquid-liquid extraction technique are presented. In acidic conditions bismuth(III) forms a yellow complex with the ligand which can be extracted in chloroform with an absorption maxima at 410 nm. The molar absorptivity is 1.5×10⁴ l mole^?1 cm^?1 and Sandell's sensitivity is 14.3 ng cm^?2. The difference in the absorbance between the chloroform blank and bismuth(III) sample increases linearly in the concentration range 2-14 ppm at 0.3 M hydrochloric acid. The proposed method is extremely sensitive, rapid, reproducible and has been satisfactorily applied to the determination of trace amounts of bismuth(III) in synthetic mixtures, alloys and pharmaceutical formulations and also provides binary separation of bismuth(III) from selenium, tellurium, lead, antimony, copper and gold. The overall process of extraction and determination takes about 15 to 20 min.