BtCH(2)TMS-assisted homologation of carboxylic acids: A safe alternative to the arndt-eistert reaction

One-carbon homologation of carboxylic acids is achieved by (i) treatment of an acyl chloride with 1-[(trimethylsilyl)methyl]-1H-1,2, 3-benzotriazole (BtCH(2)TMS) (1) to afford N-(acylmethyl)benzotriazoles 3a-f, followed by (ii) conversion of 3a-f with triflic anhydride into RC(OTf)=CHBt 4a-f, and (iii) the subsequent reaction of 4a-c with NaOCH(3) followed by 1N HCl to afford esters RCH(2)CO(2)R' 7a-c in overall yields of 50-70%. For the aliphatic compounds 5d-f, treatment of 5d-f with p-toluenesulfonic acid followed by TBAF/THF afforded acids RCH(2)COOH 7d-f.     

General and efficient insertion of carbons carrying benzotriazole

Anions formed from the lithiation of 1-(1-benzotriazolylalkyl)benzotriazoles (1, 6) and 1-(1-methylthioalkyl)benzotriazoles (10 and 10a) with n-BuLi underwent additions to cyclic and acyclic ketones giving intermediates 3a-f, 7b-f, and 11b-d, respectively, in excellent yields. Thermal rearrangements of intermediates 3a,b,d-f and 7b-d,f in the presence of zinc bromide provided one-carbon chain-extended or ring-expanded alpha-benzotriazolyl ketones 4a,b,d-f and 8b-d,f in moderate yields with excellent regioselectivity. By contrast, intermediates 11b-d on treatment with zinc bromide loose a molecule of benzotriazole followed by intramolecular cyclization of the resulting intermediates 12b-d to provide the 2,3- and 1,2,3-substituted indenes 13b-d in good yields.     

The first urea azine molecule and its coordination to uranium in the first actinide guanidinate complexes

The urea azine molecule (CyNH)(2)C=N-N=C(HNCy)(2) (1) was easily prepared by reaction of the carbodiimide CyN=C=NCy and H(2)NNH(2) and this novel type of bis-guanidine proved useful in affording chelating and bridging ligands for the building of polynuclear compounds, as illustrated by the synthesis of the first uranium guanidinate complexes [(THF)(2)Li(mu-Cl)(2)UCl(mu-L)](2) (2) and [UCl(mu-L)(2)UCl(2)(micro-Cl)(2)UCl(mu-L)](2) (3) (L = - 2H); the X-ray crystal structures of compounds - were determined.     

Evaluation of magnetic terms in Cu4O4 cubane-like systems from selected configuration interaction calculations: a case study of polynuclear transition-metal systems

We present the evaluation of magnetic terms in a Cu(4)O(4) cubane-like system from truncated CI calculations, as a case study of polynuclear transition-metal complexes. We employ a new excitation selected configuration interaction (EXSCI) method based on the use of local orbitals. Taking advantage of the locality and then of the fact that the interactions vanish when the distance is large, the dimension of the CI is largely reduced. To the best of our knowledge these CI calculations are the largest one performed for polynuclear transition metal systems so far. The results show the presence of two leading ferromagnetic interactions between bridged Cu ions. Also the interactions between the unbridged Cu ions are ferromagnetic, but very weak, in contrast to the experimental data. The nature and amplitude of all the computed interactions are consistent with the relative orientation of the magnetic orbitals in the molecule, and correctly reproduce the susceptibility versus temperature curve. Our results indicate that it is possible to obtain similar fittings with sets of parameters representing different physical effects and put in evidence the drawbacks of the fitting based on oversimplified magnetic models. In this context, the presented computational strategy can be considered as a useful tool to help in the interpretation of the magnetic data and the validation of the magnetic interaction model in the polynuclear magnetic systems.     

激活CaO-MgO-SiO_2长余辉玻璃发光性质

报道了一种新型的Eu~(2+)离子激活硅酸盐玻璃,该玻璃组成为2CaO-MgO-3SiO_2-0.015Eu_2O_3(CMSE)。通过透射光谱、稳态荧光光谱、余辉光谱和热释光等技术手段对CMSE的发光性质进行了深入研究。研究发现CMSE可以被紫光和近紫外光激发,获得黄色长余辉发光。热释光曲线的分析表明,CMSE的长余辉性质主要来自于玻璃基质中陷阱深度为0.83 e V左右的定域能级。研究认为对CMSE发光性质的研究有利于开发新型稀土离子激活近紫外激发LED用硅酸盐玻璃发光材料。     

Structural and quantum chemical analysis on 4,4′-di(2-hydroxybenzylamino)diphenylmethane

The title compound is analyzed by X-ray diffraction. ONIOM(B3LYP/6-31G(d,p):PM3) is used to investigate the optimized calculation and the frequency analysis of the molecule, in which the PM3 method was used for carbon and hydrogen atoms of the benzene ring and the B3LYP/6-31G(d,p) method was used for the other parts. Energy changes in the molecule are numerically investigated by the flexible scan at PM3 level. The nature of intramolecular interactions that stabilize the structure in vacuo and solid is studied. The results reveal that the molecule is flexible and molecular conformations can easily be mutually transformed through very small potential barriers.     

Annulated 1,2,3-triazoles. 3. Synthesis of 1,2,3-triazolo[4,5-b][1,5]benzoxazepin-10(9H)-ones and 10-(4-substituted-1-piperazinyl)-1,2,3-triazolo[4,5-b][1,5]benzoxazepines

10-(4-Substituted-1-piperazinyl)-1,2,3-triazolo[4,5-b][1,5]benzoxazepines 11 were prepared in a three-step synthesis starting from easily available 5-chloro-1,2,3-triazole-4-carbonyl chlorides 7 by titanium tetrachloride catalyzed condensation of N-(substituted)piperazines with 1,2,3-triazolo[4,5-b][1,5]benzoxazepin-10(9H)-ones 10 formed by ring closure of the intermediate amides 9 . Although lactams 10 were obtained as the sole product of the cyclisation at 80°, the unexpected by-products 13 and 14 were formed in addition to 10c at 150° from 9c . The 4-methoxybenzyl group in 11j was easily removed by solvolyses in TFA. Compounds 11d-f and 11i were tested for psychotropic activity.     

Ring-chain isomerism of 1,3,3-trimethyl-2-formylmethylene-indoline (fischer aldehyde) oxime and associated reactions

The compound 1,3,3-trimethyl-2-formylmethyleneindoline oxime is synthesized for the first time. Using the polynuclear resonance method it is shown that the oxime exists as two isomers, one of which has a cyclic structure. A number of reactions are carried out involving the carbocyclic and oxime parts of the molecule.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 183–189, February, 1992.     

Disentangling proton connectivity networks in highly overlapped 1H-NMR spectra of polynuclear aromatics using 1D-HOHAHA

One-dimensional ( 1D ) variants of two-dimensional ( 2D ) nmr techniques can frequently provide the required information in a much shorter period of time than the 2D experiment from which they were derived. Application of the 1D homonuclear Hartmann-Hahn (1D-HOHAHA) experiment to establish proton-proton connectivity networks in highly overlapped four-spin systems in the proton nmr spectra of polynuclear aromatics is described. Selective subspectra are contrasted to the data obtained in a COSY experiment on the same molecule, benzo[f][l]benzothieno [2,3 -c]quinoline. Results from the 1D-HOHAHA technique are especially useful when component resonances from several spin systems are heavily overlapped. Relayed 1D-HOHAHA provides the means of exploiting small, long range coupling pathways of polynuclear aromatics.     

L-Proline promoted fluorescent sensor for Mg2+ detection in a multicomponent sensory system

Mg(2+) can lead to the fluorescence enhancement of a dye molecule as high as 47.3-fold while L-proline acts as a promoter in this multicomponent sensory system. The fluorescence color could be easily detected by the naked eye under a UV-lamp.     

Use of an Aqueous Micellar Mobile Phase for Separation of Phenols and Polynuclear Aromatic Hydrocarbons via HPLC

Abstract

An aqueous solution of sodium dodecyl sulfate (SDS) micelles is shown to be a novel, highly effective mobile phase in high performance liquid chromatography. Using a reverse phase column, nine phenols and two polynuclear aromatic hydrocarbons were easily separated. The possible advantages and disadvantages of aqueous micellar solutions over traditional organic and mixed solvent mobile phases is discussed.     

Considering the polynuclear complexes in the ionic equilibria of the Pb2+-H2O system

Analysis of conditions of the lead hydroxide and sulfide formation in the Pb²⁺-H₂O system was carried out with accounting for the formation of polynuclear hydroxo-complexes. This allows predicting a possibility of the lead hydroxide formation in the solution before the beginning of the synthesis of lead sulfide. The domains of the stable formation of Pb(OH)₂ and PbS were calculated for the systems containing lead citrate complexes and hydroxo-complexes. The proposed calculation method can be used for the quantitative determination of the reaction mixture composition and development of the chemical deposition technology of lead chalcogenides in different morphological forms: nanocrystalline powders (hydrophobic sol), quantum dots, heterostructures of the core@shell type or films. The proposed calculation method is applicable to other chalcogenide systems containing metal ions forming mononuclear and polynuclear hydroxo-complexes.     

Multielectron-transfer reactions at single Cu(II) centers embedded in polyoxotungstates driven by photo-induced metal-to-metal charge transfer from anchored Ce(III) to framework W(VI)

Using carbon monoxide as a probe molecule for the oxidation state of Cu ions, we demonstrated that anchored polynuclear charge-transfer complexes consisting of Ce(III) ions and Cu(II)-substituted Keggin-type polyoxotungstates function as efficient visible-light-driven multielectron-transfer catalysts.     

Regularities in the retention of nonsubstituted polynuclear aromatic hydrocarbons in liquid chromatography on polar adsorbents

Summary The retention of polynuclear aromatic hydrocarbons (PAH) is studied in liquid chromatography, using columns packed with silica gel with a hydroxylated surface and the same silica gel with surface-bonded amine and nitrile groups. A linear relationship was found between retention and the number of π-electrons in the molecule, the size of the molecule and the different types of carbon atoms in the molecule. The different carbon atoms in a PAH molecule contribute differently to the retention and this contribution depends on the nature of the polar functional groups on the adsorbent's surface and on the nature and concentration of a polar modifier present in a non-polar eluent.     

Reversible luminescence switching of a redox-active ferrocene-europium dyad

The copper-catalyzed cycloaddition reaction between a propargyl-appended europium complex and azidomethylferrocene yields a d-f dyad whose photophysical properties can be reversibly switched by varying the oxidation state of the ferrocene chromophore.     

Electronic basis of the comparable hydrogen bond properties of small H2CO/(H2O)n and H2NO/(H2O)n systems (n = 1, 2)

The electronic and structural properties of dihydronitroxide/water clusters are investigated and compared to the properties of formaldehyde/water clusters. Exploring the stationary points of their potential energy surfaces (structurally, vibrationally, and energetically) and characterizing their hydrogen bonds (by both atoms in molecules and natural bond orbitals methods) clearly reveal the strong similarity between these two kind of molecular systems. The main difference involves the nature of the hydrogen bond taking place between the X-H bond and the oxygen atom of a water molecule. All the properties of the hydrogen bonds occurring in both kind of clusters can be easily interpreted in terms of competition between intermolecular and intramolecular hyperconjugative interactions.     

Synthesis, characterization and photophysical properties of PPh2-C2-(C6H4)n-C2-PPh2 based bimetallic Au(I) complexes

A family of the diphosphines PPh(2)C(2)(C(6)H(4))(n)C(2)PPh(2) (n = 0-3), which possess a dialkynyl-arene spacer between the phosphorus atoms, was used for the synthesis of a series of bimetallic gold(I) complexes 1-7. Unlike the corresponding polynuclear Au(i) clusters, which show unique phosphorescence, 1-7 reveal dual emissions consisting of fluorescence and phosphorescence. The results are rationalized, in a semi-quantitative manner, by the trace (1-3) to zero (4-7) contribution of MLCT varying with the number of conjugated phenylene rings. As a result, unlike typical polynuclear Au(I) clusters with 100% triplet state population, the rate constant of the S(1)→T(1) intersystem crossing is drastically reduced to 10(9) s(-1) (4-7)-10(10) s(-1) (1-3), so that the fluorescence radiative decay rate can compete or even dominates. The drastic O(2) quenching of phosphorescence demonstrates the unprotected nature of the emission chromophores in 1-7, as opposed to the well protected, O(2) independent phosphorescence in most multimetallic Au(I) clusters.     

Tetrazoles as ligands,part I. Transition metal(II) salts and complexes of 5-cyanotetrazole

Summary Transition metal(II) ions and 5-cyanotetrazole (CNHT) form two types of compounds; type I with two 5-cyanotetrazolate (CNT) ions and an additional CNHT molecule and type II with only the two [CNT]^– ions. Water molecules are invariable included in all compounds and are considered to be essential for the existence of the crystal structure. The complexes were identified and characterized by chemical analyses, i.r. and ligand field spectra. Some structural features have been predicted from these spectra and a polynuclear complex formation is apparent.     

Fine‐tuning the Local Symmetry to Attain Record Blocking Temperature and Magnetic Remanence in a Single‐Ion Magnet

Remanence and coercivity are the basic characteristics of permanent magnets. They are also tightly correlated with the existence of long relaxation times of magnetization in a number of molecular complexes, called accordingly single‐molecule magnets (SMMs). Up to now, hysteresis loops with large coercive fields have only been observed in polynuclear metal complexes and metal‐radical SMMs. On the contrary, mononuclear complexes, called single‐ion magnets (SIM), have shown hysteresis loops of butterfly/phonon bottleneck type, with negligible coercivity, and therefore with much shorter relaxation times of magnetization. A mononuclear Er^III complex is presented with hysteresis loops having large coercive fields, achieving 7000 Oe at T=1.8 K and field variation as slow as 1 h for the entire cycle. The coercivity persists up to about 5 K, while the hysteresis loops persist to 12 K. Our finding shows that SIMs can be as efficient as polynuclear SMMs, thus opening new perspectives for their applications.