Bornane with integrated push–pull butadienes

The {3-[bis(alkylthio)methylene]-1,7,7-trimethyl-bicyclo[2.2.1]hept-2-ylidene}malononitriles ((1R,4S)- 2 , (1S,4R)- 2 and (1R,4S)- 3 ) were prepared starting from 1,7,7-trimethyl-bicyclo[2.2.1]hept-2-ylidenemalononitriles (1R, 4R)- 1 and (1S,4S)- 1 ) arisen from (+)-, (–)-camphor. The reaction of (1R,4S)- 2 with bromine yielded the (1S,8R)-8,11,11-trimethyl-3-methylthio-5-oxo-4-thiatricyclo-[6.2.1.0^2,7]undeca-2,6-diene-6-carbonitrile ( 8 ) after hydrolysis of the initially formed (1S,8R)-6-cyano-8,11,11-trimethyl-3-methylthio-4-thia-tricyclo[6.2.1.0^2,7]undeca-2,6-diene-5-iminium bromide ( 7 ).     

Efficient synthesis of functionalized bis-(4-oxo-1,3-thiazolan-5-ylidene)acetates

Reaction of 1-(2,2-dimethyl-propionyl)-3-{4-[3-(2,2-dimethyl-propionyl)thioureido]phenyl}thiourea or 1-(2,2-dimethyl-propionyl)-3-{5-[3-(2,2-dimethyl-propionyl)thioureido]naphthalen-1-yl}thiourea with dialkyl acetylenedicarboxylates in CH₂Cl₂ leads to alkyl (2-(2,2-dimethyl-propionylimino)-3-{4-[-(,2-dimethyl-propionylimino)-5-alkoxycarbonylmethylene-4-oxo-thiazolidin-3-yl]-phenyl}-4- oxo-thiazolidin-5-ylidene)acetates or alkyl (2-(2,2-dimethyl-propionylimino)-3-{5-[2-(2,2-dimethyl-propionylimino)-5-alkoxycarbonylmethylene-4-oxo-thiazolidin-3-yl]naphthalen-1-yl}-4-oxo-thiazo lidin-5-ylidene)acetates in good yields.     

Structure-HDS Reactivity Relationship of Dibenzothiophenes Based on Density Functional Theory

Perpendicular adsorption of alkyl-substituted dibenzothiophenes on a Mo₁₀S₁₈cluster was studied using density functional theory. The Mayer bond order between the sulfur atom of dibenzothiophene and the molybdenum atom of the Mo₁₀S₁₈cluster was calculated from the optimized adsorption complex. Depending on the position of the alkyl substitution in dibenzothiophene, the values of the Mayer bond order were classified into three groups, and compared with the experimental hydrodesulfurization (HDS) rate constants measured at 320 °C, 70 atm, and 1. 6 h^-1over a NiMo/Al₂O₃catalyst using a light cycle oil.     

Redox Potentials of High-Valent Iron-, Cobalt-, and Nickel-Oxido Complexes: Evidence for Exchange Enhanced Reactivity

The ferrocene titration method has been employed to determine the one-electron reduction potentials of a series of oxido-iron(IV), oxido-cobalt(IV) and oxido/hydroxido-nickel(III) complexes based on the same tetradentate TMG₃tren ligand (TMG₃tren=tris[2-(N-tetramethylguanidyl)ethyl]amine). The S=2 ground state of the [(TMG₃tren)Fe^IV=O]²⁺ complex allows an exchange enhanced reactivity, which enables it to perform efficient oxygen atom transfer (OAT) and hydrogen atom abstraction (HAA) reactions with a low one-electron reduction potential of 270 mV vs. SCE. In the absence of exchange enhanced reactivity, the OAT and HAA abilities of the S=3/2 [(TMG₃tren)Co^IV−O(Sc(OTf)₃)]²⁺, S=1/2 [(TMG₃tren)Ni^III−O(H)]²⁺ and the previously reported S=1 [(TMC)(CH₃CN)Fe^IV=O]²⁺ and [(N4Py)Fe^IV=O]²⁺ complexes can be directly correlated to their reduction potentials. Notably, [(N4Py)Fe^IV=O]²⁺ and [(TMG₃tren)Fe^IV=O]²⁺ exhibit similar OAT and HAA reactivities although the reduction potential of [(N4Py)Fe^IV=O]²⁺ is 0.24 V more positive than that of [(TMG₃tren)Fe^IV=O]²⁺. The present study therefore provides experimental evidence for exchange enhanced reactivity and rationalizes nature's choice for employing S=2 oxido-iron(IV) cores to achieve difficult oxidation reactions at biologically viable potentials.     

Analysis of the spectroscopic parameters of chalcogenide glasses in the Ga-Ge-S: Er3+ system

The spectroscopic characteristics of chalcogenide glasses in the Ga-Ge-S: Er³⁺ system are determined. The oscillator strengths, the Judd-Ofelt intensity parameters, the probabilities of spontaneous radiative transitions, and the radiative lifetimes of levels are calculated from the absorption spectroscopy data for two series of Ga-Ge-S chalcogenide glasses doped with Er³⁺ ions. In the first series, the Er₂S₃ content is varied from 0.49 to 4.64 mol % at the fixed composition of the glass matrix (0.15Ga₂S₃ · 0.85GeS₂). In the second series, the Ga₂S₃ content is varied from 10 to 30 mol % at the fixed Er₂S₃ content (1.94 mol %). The aforementioned spectroscopic parameters are analyzed as a function of the chalcogenide glass composition. It is revealed that the values of the oscillator strengths and the probabilities of spontaneous radiative transitions in Er³⁺ ions in the chalcogenide matrix are larger than those in phosphate, germanate, and tellurite matrices.     

Four new cyclometalated phenylisoquinoline-based Ir(III) complexes: Syntheses,structures, properties and DFT calculations

Four new cyclometalated phenylisoquinoline-based iridium(III) complexes [Ir(C^∧N)₂(bipy)]PF₆ (5a–5d) (bipy = 2,2′-bipyridine) have been synthesized and fully characterized, where the C^∧N ligands are 1-(4-(trifluoromethyl)phenyl)isoquinoline, 4-(isoquinolin-1-yl)benzaldehyde, 4-(isoquinolin-1-yl)benzonitrile and 1-(3-fluoro-4-methylphenyl)isoquinoline, respectively. The crystal structures of 5a and 5c have been determined. The photophysical and electrochemical properties of these new complexes 5a–5d have been studied. All Ir(III) complexes exhibit orange phosphorescence in dichloromethane solution at room temperature with a maximum at 593–618 nm, quantum yield of 0.046–0.16. The frontier molecular orbital diagrams and the lowest-energy electronic transitions of 5a–5d have been calculated with density functional theory (DFT) and time-dependent DFT (TD-DFT).     

Electrochemical reduction of sulphur in dimethylacetamide

The electrochemical reduction of sulphur into S^2?₈ and S^?₃, then into S^2?₄ has been studied in dimethylacetamide in order to prove that neither the disproportionation of S^2?₈, nor the direct electroreduction of S^2?₈ could be neglected to explain the mechanism of the electroreduction of S₈. A good fit between calculated and experimental visible absorbance or electrochemical curves recorded during coulometric experiments could be obtained without introducing the S^?₄ radical proposed in the literature.Equilibrium constants have been determined

.An estimation of the basicity of S^2?₈ and S^2?₃ ions is deduced from voltammetric curves recorded during the electrolysis of S₈ solutions.     

Synthesis,characterization and molecular structure of Re(III) complexes containing 2-benzoylpyridine

The paper presents a combined experimental and computational study of Re(III) complexes containing 2-benzoylpyridine (bopy). Two novel complexes [ReX₃(bopy)(PPh₃)] (X = Cl, Br) have been obtained in the reactions of [ReX₃(MeCN)(PPh₃)₂] with 2-benzoylpyridine in dichloromethane and have been studied by IR, UV–Vis spectroscopy and X-ray crystallography. The electronic structure of [ReCl₃(bopy)(PPh₃)] has been calculated with the density functional theory (DFT) method. The spin-allowed electronic transitions of [ReCl₃(bopy)(PPh₃)] have been calculated with the time-dependent DFT method and the UV–Vis spectrum has been discussed on this basis.     

A fragmentary model of vitreous As<Subscript>2</Subscript>S<Subscript>3</Subscript>

The X-ray scattering intensity curves for vitreous As₂S₃ are experimentally measured using soft (copper) and hard (molybdenum) X rays. The inclusion of all the specific features revealed in the experimental scattering intensity curves makes it possible to obtain the experimental atomic radial distribution function (ARDF) in the ordering range up to ～1 nm. The experimental ARDF is interpreted in the framework of the fragmentary model. A comparison of the experimental ARDF with the model ARDF calculated from the crystal structure data obtained for orpiment demonstrates that the corrugated layers inherent in crystalline As₂S₃ are retained in the glass structure but the characteristic interlayer interatomic distances are absent. The layers are joined together through the As₄S₅ molecular clusters. Microcrystals consisting of several unit cells are absent in the glass structure, which involves only the structural fragments of both crystalline analogs. One of the possible variants of their joining is proposed.     

Nucleophilic addition of water to 1-isoquinolinyl phenyl ketone. The synthesis, spectroscopic investigation, crystal and molecular structure and DFT calculations of [ReOBr2(iquinpk-OH)(PPh3)]

The reaction of [ReOBr₃(PPh₃)₂] with 1-isoquinolinyl phenyl ketone in acetone has been examined and the novel complex [ReOBr₂(iquinpk-OH)(PPh₃)] has been obtained. The complex has been characterised by IR, UV–Vis spectroscopy and X-ray crystallography. The electronic structure of [ReOBr₂(iquinpk-OH)(PPh₃)] has been calculated with the density functional theory (DFT) method. The spin-allowed electronic transitions of [ReOBr₂(iquinpk-OH)(PPh₃)] have been calculated with the time-dependent DFT method and the UV–Vis spectrum has been discussed on this basis.     

Synthesis and Highly Stereoselective Hydrogenation of the Statin Precursor Ethyl (5S)‐5,6‐Isopropylidenedioxy‐3‐oxohexanoate

A search for the large‐scale preparation of (5S)‐5,6‐(isopropylidenedioxy)‐3‐oxohexanoates ( 2 ) – a key intermediate in the synthesis of pharmacologially important statins – starting from (S)‐malic acid is described. The synthesis of the required initial compound methyl (3S)‐3,4‐(isopropylidenedioxy)butanoate ( 1 ) by Moriwake’s reduction of dimethyl (S)‐malate ( 3 ) has been improved. Direct 2‐C chain elongation of ester 1 using the lithium enolate of tert‐butyl acetate has been shown to be successful at a 3‐ to 5‐fold excess of the enolate. Unfortunately, the product, tert‐butyl (5S)‐5,6‐(isopropylidenedioxy)‐3‐oxohexanoate ( 2a ) is unstable during distillation. Ethyl (5S)‐5,6‐(isopropylidenedioxy)‐3‐oxohexanoate ( 2b ) was prepared alternatively on a multigram scale from (3S)‐3,4‐(isopropylidenedioxy)butanoic acid ( 7 ) by activation with N,N′‐carbonyldiimidazole and subsequent reaction with Mg(OOCCH₂COOEt)₂. A convenient pathway for the in situ preparation of the latter is also described. Ethyl ester ( 2b ) can be advantageously purified by distillation. The stereochemistry of the catalytic hydrogenation of β‐keto ester ( 2b ) to ethyl (5S)‐5,6‐(isopropylidenedioxy)‐3‐hydrohyhexanoate (syn‐ 6 and anti‐ 6 ) has been studied using a number of homogeneous achiral and chiral Rh(I) and Ru(II) complexes with phosphine ligands. A comparison of Rh(I) and Ru(II) catalysts with (S)‐ and (R)‐BINAP as chiral ligands revealed opposite activity in dependence on the polarity of the solvent. No influence of the chiral backbone of substrate 2b on the enantioselectivity was noted. A ratio of syn‐ 6 /anti‐ 6 =2.3 was observed with an achiral (Ph₃P)₃RuCl₂ catalyst. Ru[(R)‐Tol‐BINAP]Cl₂ neutralized with one equivalent of AcONa afforded the most efficient catalytic system for the production of optically pure syn‐(5S)‐5,6‐isopropylidenedioxy‐3‐hydroxyhexanoate (syn‐ 6 ) at a preparative substrate/catalyst ratio of 1000:1.     

A novel chloro-bridged tetranuclear cadmium(II) cluster with pyridyl-substituted nitronyl nitroxide: structure and magnetic properties

A tetranuclear cadmium(II) complex of 2(2-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1 H-imidazol-1-oxy 3-N-oxide (NIToPy) with CdCl₂,[Cd₄Cl₈(NIToPy)₄], has been structurally and magnetically characterized. The structure is based on a novel chloro-bridged tetranuclear cadmium quasi-cubane cluster, in which each cadmium atom is chelated by one NIToPy radical, and coordinated with four bridging chlorine atoms. The temperature dependence of the magnetic susceptibility measurements shows a weak ferromagnetic coupling between the radicals. An excellent simulation of the experimental data with the prism type four spins Hamiltonian H=−2J₁(S₁S₂+S₂S₃+S₃S₄+S₁S₄)−2J₂S₂S₄ obtained the parameters: J₁=1.12 cm⁻¹, J₂=−0.20 cm⁻¹, and g=2.04.     

Highly efficient and versatile one-pot synthesis of substituted thienylidene compounds

A novel, efficient, and very mild one-pot synthesis of methyl 2-[(Z)-4-aryl-5-morpholino-3-oxo-2,3-dihydrothiophen-2-ylidene]acetate derivatives under kinetic control has been developed. The title compounds were prepared by the reaction of thioacetomorpholides with dimethyl acetylene-dicarboxylate (DMAD) in the presence of K₂CO₃ in a non-polar solvent with excellent yields.     

Molecular structures and vibrational frequencies for cis-[PdCl2(tmen)] and cis-[Pd(N3)2(tmen)]: A DFT study

Theoretical molecular structures of the complexes cis-[PdCl₂(tmen)] and cis-[Pd(N₃)₂(tmen)] (tmen = N,N,N′,N′-tetramethylethylenediamine) were investigated using B3LYP/DFT method. The calculated molecular parameters, bond distances and angles, revealed a square-planar geometry around the metallic center for both compounds with the azide being linear. The theoretical infrared spectra of C₁ symmetry (electronic state ¹A) of the compounds are in agreement with the experimental data.     

Elektronische und sterische Substituenteneinflüsse auf die UV/VIS-Absorptionsspektren der Phenylfulgidisomeren

Electronic and Steric Substituent Influences on the U.V./VIS-Absorption Spectra of Phenylfulgide Isomers The u.v./vis spectral data of a large number of phenylfulgides (E-, Z-, E-E-, E-Z-, Z-E-, Z-Z-isomers, 1.8a-dihydronaphthalenes) are presented. An increase of the number of phenyl rings as well as substitution of the phenyl rings cause correlatable bathochromic spectral shifts. Steric influences became obvious by introducing methyl groups, by coplanarization of phenyl groups and in the series of isomers. By means of PPP calculations shifts in position and/or intensity of absorption bands are ascribed to the substituent effects. The calculated band polarization of E(E-E)-isomers are in agreement with the results of polarization spectra in oriented liquid crystal mesophases. The polarization spectra allow the assignment of the longwave absorption band to the S₂ ← S₀ and S₁ ← S₀ electronic transitions for E-E-Isomers with a C_2v-symmetry.     

Spektrometrische Untersuchungen an N,N′-disubstituierten Dithiomalonsäurediamiden und ihren Kobalt(II)-Komplexen

Spectroscopical Investigations on N,N′-Disubstituted Dithiomalonamides and their Co(II)-Complexes The Co(II)-complexes of N,N′-disubstituted dithiomalonamides have been synthesized and characterized. Comparative uv/vis-, ir-, epr-, x-ray-, and n.m.r.-spectral studies of this complexes and of the dithiomalonamides suggest that their Co(II)-compounds are S₄-coordinated square planar inner complexes (CoL₂). The orbital splitting parameters Δ of these complexes have been calculated in the order of less than 20000 cm⁻¹. For compounds CoL₂ by this way the following spectrochemical series of the ligands results: dmma < d cl_mma < dnma < d cl_pma < dpma. All dithiomalonamides investigated in this work exist nearly complete in the dithion-form.     

Different Hemi-Salen/Salan Ligand Containing Binuclear Boron-Fluoride Complexes: Synthesis,Spectroscopy, Fluorescence Properties,and Catalysis

A family of hemi-salen (L₁H–L₆H) and hemi-salan (L_1aH–L_2aH) ligands-based N,O-chelated binuclear boron-fluoride [L_n(BF₂)₂] (n = L₁–L₆ or L_1a–L_2a) complexes have been prepared and characterized by a variety of spectroscopic techniques (¹H, ¹³C and ¹⁹F NMR, FT-IR, UV-Vis, LC-MS, and fluorescence spectra) and elemental analysis. All of the binuclear boron-fluoride complexes exhibit strong absorption bands due to S₀→S₁ transitions and strong fluorescence properties were observed at room temperature in the solution. The binuclear boron complexes containing two naphthyl groups are significantly red-shifted in comparison with the other binuclear boron-fluoride complexes. After the structures are characterized, these hemi-salen and salan ligand-based N, O-chelated binuclear boron-fluoride complexes were utilized to the transfer hydrogenation of the different acetophenone derivatives conversion to 1-phenylethanol derivatives as catalysts.     

Experimental and Computational Evaluation of Piperonylic Acid Derived Hydrazones Bearing Isatin Moieties as Dual Inhibitors of Cholinesterases and Monoamine Oxidases

A set of piperonylic acid derived hydrazones with variable isatin moieties was synthesized and evaluated for their inhibitory activity against the enzymes acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and monoamine oxidases A and B (MAO-A/B). The results of in vitro studies revealed IC₅₀ values in the micromolar range, with the majority of the compounds showing selectivity for the MAO-B isoform. N-[2-Oxo-1-(prop-2-ynyl)indolin-3-ylidene]benzo[d][1,3]dioxole-5-carbohydrazide ( 3 ) was identified as a lead AChE inhibitor with IC₅₀=0.052±0.006 μm . N-[(3E)-5-chloro-2-oxo-2,3-dihydro-1H-indol-3-ylidene]-2H-1,3-benzodioxole-5-carbohydrazide ( 2 ) was the lead MAO-B inhibitor with IC₅₀=0.034±0.007 μm , and showed 50 times greater selectivity for MAO-B over MAO-A. The kinetic studies revealed that compounds 2 and 3 displayed competitive and reversible inhibition of AChE and MAO-B, respectively. The molecular docking studies revealed the significance of hydrophobic interactions in the active site pocket of the enzymes under investigation. Further optimization studies might lead to the development of potential neurotherapeutic agents.     

Anisotropic field induced phase transitions and negative electrocaloric effect in rhombohedral Mn doped Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals

The electrocaloric effect (ECE) of Mn doped Pb(In_1/2Nb_1/2)O₃-Pb(Mg_1/3Nb_2/3)O₃-PbTiO₃ (PIN-PMN-PT:Mn) single crystals with particular emphasis on the impact of crystallographic orientations and phase transitions were investigated systematically. Orientation-dependent phase transitions have been demonstrated by the dielectric and strain behaviors. Intriguingly, the negative ECE of –0.02?°C and –0.002?°C were obtained firstly in [001]-oriented PIN-PMN-PT:Mn crystals near the rhombohedral→tetragonal phase transformation and in [011]-oriented crystals near the rhombohedral→orthorhombic phase transformation, respectively. However, only the positive ECE was found in [111]-oriented crystals near the tetragonal→rhombohedral phase transition. Additionally, the maximum ECE temperature changes calculated in [001]-, [011]- and [111]-oriented crystals were 0.33?°C, 0.46?°C and 0.38?°C, respectively. Our results suggest that the negative ECE is attributed to electric field-induced phase transitions, whose critical field decreases with the increase of temperature. The phase transition-mediated coexistence of positive and negative effects in the relaxor-ferroelectric single crystals is beneficial to enhance the efficiency of the solid-state cooling devices.     

Rhodium complexes with a new chiral amino-phosphinite ligand and their behavior as pre-catalysts in the hydroformylation of styrene

The new amino-phosphinite chiral ligand (S_a)-4-((S)-1-(diphenylphosphinooxy)-3-methylbutan-2-yl)-4,5-dihydro-3H-dinaphtho[2,1-c:1′,2′-e]azepine (1) has been synthesized and the corresponding more stable oxide has been characterized by X-ray analysis. The ligand behavior in styrene hydroformylation using [Rh(acac)(CO)₂] and [Rh(COD)₂]BF₄ as precursors has been studied. With both pre-catalysts, branched aldehyde 2-phenylpropanal was obtained in mild catalysis conditions with high yield and regioselectivity but as racemic mixture, indicating the loss of the ligand (1) during catalytic run. To support these results, the reactions of [Rh(acac)(CO)₂] and [Rh(COD)₂]BF₄ with the ligand 1 have been performed and the pre-catalysts behavior under CO/H₂ has been investigated.