Formation of complexes of Rubisco-Rubisco activase from La~(3+), Ce~(3+) treatment spinach

It has been proved by many early researches thatrare earth elements (REEs) could improve photosyn-thesis. However, the studies were mainly focused onthe effects of REEs on the absorption of light energy,transforming light energy into electron energy, elec…     

Reexamination of CeCl3 and InCl3 as activators in the diastereoselective Mukaiyama aldol reaction in aqueous media

A search for suitable reaction conditions in Mukaiyama-type aldol condensations activated by CeCl(3) and InCl(3) revealed that the reaction proceeds best in i-PrOH/H(2)O (95:5). Contrary to literature precedent, no reaction was observed in pure water, and the encountered destruction of the starting silyl enol ether can be ascribed to initial hydrolysis of the Lewis acid. As anticipated from the dual parameter (pK(h), WERC value) characteristics of CeCl(3) and InCl(3), the former proved more efficient as Lewis acid-promoter, in terms of reaction speed and yield. Nevertheless, InCl(3) was a superior catalyst during evaluation of the diastereoselectivity of the process. In this regard, determination of diastereoselectivity as a function of time showed that the InCl(3)-catalyzed reaction is irreversible, whereas the CeCl(3)-catalyzed reaction is a reversible process. In both cases, formation of the syn product is kinetically preferred, although DeltaDeltaG(++)273K(InCl(3)) = 1.50 kcal/mol versus DeltaDeltaG(++)273K (CeCl(3)) = 0.38 kcal/mol. Molecular modeling (semiempirical PM3, ab initio HF/3-21G*, hybrid B3LYP/3-21G*, and B3LYP/LANL2DZ) of the diastereoselective aldol reaction promoted by InCl(3) supports a "closed", Zimmermann-Traxler transition state.     

Al合金铈盐转化膜缓蚀机理研究

Ce盐作为一种环境友好的Al合金缓蚀剂日益受到重视 ,但缓蚀机理还不很清楚 .本文应用自行研制的扫描微参比电极技术 (SMRE) ,原位测量经CeCl3处理和未处理过的 2 0 2 4 T3Al合金表面微区电位分布 ,并用扫描电子显微镜 (SEM )和X 射线能量散射谱 (EDS)表征样品形貌特征 ,结合其它电化学技术 ,对Ce盐缓蚀机理作了深入探讨 .结果表明 ,经Ce盐处理的Al合金表面可形成一层不均匀分布的转化膜 ,抑制了O2 和电子传输 ,表现为一种优良的阴极缓蚀特性     

Al合金表面Ce转化膜成膜机理研究

Ce转化膜作为一种Cr转化膜的理想替代品而日益受到人们的重视，但其成膜机理还不很清楚.本文应用自行研制的扫描微参比电极技术（SMRE），原位测量经CeCl3溶液处理的2024-T3 Al合金表面微区电位分布，并结合X光电子能谱（XPS）和交流阻抗谱（EIS），对Ce转化膜的成膜机理进行探讨.结果表明，在CeCl3溶液中，Ce转化膜的形成过程是 Ce3＋和Cl－相互竞争的动态过程.当由Cl－的不均匀吸附引起的局部腐蚀使pH升高时， Ce(OH)3就会首先在局部位置发生沉积.阴极反应过程产生的H2O2可将Ce(OH)3部分氧化成CeO2.     

Ru-Catalyzed asymmetric hydrogenation of alpha-ketoesters with CeCl3.7H2O as additive

[reaction: see text] An efficient asymmetric hydrogenation of alpha-ketoesters is reported with use of a catalyst prepared from [Ru((S)-3)(benzene)Cl]Cl and CeCl(3).7H(2)O. Alpha-hydroxy esters are obtained in up to 96% ee. The addition of CeCl(3).7H(2)O not only improves the enantioselectivity, but also enhances the stability of the catalyst. As a result, the hydrogenation of methyl benzoylformate affords the product with 92% ee with a substrate/catalyst ratio of 10 000. Hydrolysis of 2 provides the final compound with 83% yield at 99% ee after a single recrystallization from 1,2-dichloroethylene.     

Mass spectrometric and quantum chemical studies of the thermodynamics and bonding of neutral and ionized LnCl, LnCl2, and LnCl3 species (Ln = Ce, Lu)

The mass spectral patterns of CeCl3(g) and LuCl3(g) and appearance energies for the identified ions were measured using a Nier-type mass spectrometer coupled with a Knudsen cell. The molecular ion CeCl3+ was found to be considerably less stable in comparison to LuCl3+. Partial pressures and sublimation enthalpies of LnCl3(s) to monomeric LnCl3(g) and dimeric Ln2Cl6(g) species were obtained in the ranges of 882-1028 (Ln = Ce) and 850-1004 K (Ln = Lu). The contribution of dimeric Ce2Cl6(g) species to equilibrium vapors of CeCl3(s) is considerably smaller than the Lu2Cl6(g) contribution in LuCl3(s) vapors. The measurements were supplemented by quantum chemical ab initio studies of structures, energetics, and vibrational frequencies of neutral and singly ionized LnCl, LnCl2, and LnCl3 species (Ln = Ce, Lu). The theoretical appearance energies of different ions, calculated from the energies of the gaseous species, are in good agreement with experimental data. The fragmentation energies of LnCl, LnCl2, and LnCl3 were also computed and compared with the mass spectral patterns of respective vapor species. The Mulliken and natural bond orbital electron population methods were applied for the systematic analysis of the bonding scheme in molecules and cations.     

Efficient transformation of azides to primary amines using the mild and easily accessible CeCl3.7H2O/NaI system

Because of the nitrogen functionality, the azido group plays an important role in the synthesis of amines, and numerous reduction methods of azides to primary amines are reported. Recent reports have highlighted the capability of NaI as a useful reagent for this transformation when it is used in combination with a Lewis acid promoter. However, these methods often suffer from harsh reaction conditions; for this reason, the development of a simple and efficient protocol using NaI in presence of inexpensive and readily available cerium salts Lewis acids would extend the scope of this organic transformation. In continuation of our interest on the use of the CeCl3.7H2O/NaI system, in this paper we report how azides undergo reduction by NaI in the presence of CeCl3.7H2O in refluxing acetonitrile under neutral conditions to produce the corresponding primary amines. The rate and yield of the reaction are considerably improved by employing this microwave-assisted procedure, and this may be of value for the preparation of densely functionalized molecules having biological and pharmaceutical activities.     

Trisannelation of acrylates to 1,3,5-benzenetricarboxylates by a Pd(OAc)2/HPMoV/CeCl3/O2 system

A new type of trisannelation reaction of acrylates through acetal formation was developed by Pd(OAc)2 combined with molybdovanadophosphoric acid (HPMo8V4) and Lewis acid under atmospheric dioxygen. Thus, the reaction of isobutyl acrylate in the presence of Pd(OAc)2, HPMo8V4, and CeCl3 under O2 (1 atm) in MeOH/AcOH afforded isobutyl 1,3,5-benzenetricarboxylate in fair yield. The reaction was found to proceed through the palladium-catalyzed acetalization of acrylate with methanol followed by the trisannelation reaction of the resulting acetal promoted by CeCl3.     

Vapor species over cerium and samarium trichlorides, enthalpies of formation of (LnCl(3))(n) molecules and Cl-(LnCl(3))(n) ions

A Knudsen effusion cell mass spectrometric technique was used to study vapor species over CeCl(3) and SmCl(3). Monomer, dimer, and trimer (Sm(3)Cl(9)) molecules, and LnCl(4-), Ln(2)Cl(7-), Ln(3)Cl(10-) (Ln = Ce, Sm) negative ions, were observed in saturated vapor in the temperature range 958-1227 K. Partial vapor pressures of neutral constituents were determined and the enthalpies of sublimation (Delta(s)H, 298 K, kJ.mol(-1)) to monomers and associated molecules obtained: 328 +/- 6 (CeCl(3)), 306 +/- 6 (SmCl(3)), 453 +/- 16 (Ce(2)Cl(6)), 408 +/- 12 (Sm(2)Cl(6)), and 468 +/- 40 (Sm(3)Cl(9)). Equilibrium constants for various chemical reactions were measured and the enthalpies of reactions obtained using the second and third laws of thermodynamics. The enthalpies of formation (Delta(f)H, 298 K, kJ.mol(-1)) of molecules and ions have been calculated as follows: -730 +/- 6 (CeCl(3)), -722 +/- 6 (SmCl(3)), -1663 +/- 16 (Ce(2)Cl(6)), -1649 +/- 13 (Sm(2)Cl(6)), -2617 +/- 40 (Sm(3)Cl(9)), -1250 +/- 15 (CeCl(4)(-)), -1252 +/- 15 (SmCl(4-)), -2184 +/- 35(Ce(2)Cl(7-)), -2172 +/- 26 (Sm(2)Cl(7-)), -3183 +/- 43 (Ce(3)Cl(10-)), and -3147 +/- 43 (Sm(3)Cl(10-)).     

Efficient synthesis of rare sugar D-allal via reversal of diastereoselection in the reduction of protected 1,5-anhydrohex-1-en-3-uloses: protecting group dependence of the stereoselection

D-allal was selectively obtained by reducing bulky-silyl-protected 1,5-anhydrohex-1-en-3-uloses using the NaBH4CeCl3 x 7 H2O system. The crucial point of this synthesis is the nature of the protecting group. When bulky silyl group such as t-butyldiphenylsilyl was used as substrate, protected D-allal was obtained in >99% selectivity. In contrast, when acetylated enone was used, protected D-glucal was obtained exclusively. The addition of CeCl3 x 7 H2O was also found to influence selectivity.     

CeCl3.7H2O: an effective additive in Ru-catalyzed enantioselective hydrogenation of aromatic alpha-ketoesters

In the presence of catalytic amounts of CeCl 3.7H 2O, [RuCl(benzene)(S)-SunPhos]Cl is a highly effective catalyst for the asymmetric hydrogenation of aromatic alpha-ketoesters. A variety of ethyl alpha-hydroxy-alpha-arylacetates have been prepared in up to 98.3% ee with a TON up to 10,000. Challenging aromatic alpha-ketoesters with ortho substituents are also hydrogenated with high enantioselectivities. The addition of CeCl 3.7H 2O not only improves the enantioselectivity but also enhances the stability of the catalyst. The ratio of CeCl 3.7H 2O to [RuCl(benzene)(S)-SunPhos]Cl plays an important role in the hydrogenation reaction with a large substrate/catalyst ratio.     

Dual-stimuli responsive behaviors of diblock polyampholyte PDMAEMA-b-PAA in aqueous solution

The rheological behaviour of aqueous suspensions of boehmite (AlO(OH)) modified with different Ce-salts (Ce(NO(3))(3), CeCl(3), Ce(CH(3)COO)(3) and Ce(2)(SO(4))(3)) was investigated at a fixed Ce/Al molar ratio (0.05). Freshly prepared boehmite suspensions were near-Newtonian and time-independent. A shear-sensitive thixotropic network developed when Ce-salts with monovalent anions were introduced in the nanoparticle sols. The extent of particle aggregation dramatically increased with ageing for Ce(NO(3))(3) and CeCl(3) whereas an equilibrium value was reached with Ce(CH(3)COO)(3). The addition of Ce(2)(SO(4))(3) with divalent anions involved no thixotropy but rather a sudden phase separation. The combined data set of IRTF and DRIFT spectra indicated that free NO(3)(-) anions of peptized boehmite adsorb on the nanoparticle surface by H-bond. The introduction of Ce-salts in the boehmite sol led to the coordination between Ce(3+) ions and NO(3)(-) anions adsorbed on boehmite i.e. to [Ce(NO(3))(4)(H(2)O)(x)](-) complex. Such coordination led to a thixotropic behaviour which was lower with Ce(NO(3))(3) compared to CeCl(3) and Ce(CH(3)COO)(3). In contrast, Ce(2)(SO(4))(3) formed insoluble complexes with dissolved aluminium species. The formation of H-bonded surface nitrate complexes was found to play a decisive role on the particle-particle interactions and consequently on the rheological behaviour of the sols.     

Effect of Ce~(3+) on spectral characteristic of D1/D2/Cytb559 complex from spinach

In our early researches, lanthanum and cerium could enter plant and bind to porphyrin of chlorophyll to form Ln3+-chllorophyll. La and Ce greatly increase photosystem II (PSII) activity and PSII electron transport rate, and the fluorescence emission peaks of PSII are blue-shifted [1—4]. Do REEs coordinate with PSII reaction center complex in vivo? Moreover, do REEs coordinate with D1(30 kD)/D2(32 kD)/Cytb559 (~9 kD) reaction center complex of site of producing pri-mary reaction-p…     

羰基化合物及其与卤代烃在CeCl_3/萘锂试剂作用下的反应

用萘锂(LiNp)还原无水CeCl_3制得的活性金属铈(Ce~*)在与羰基化合物的反应中,与用相同方法制得的Nd~*相比,表现出更高的反应活性。Ce~*与羰基化合物反应经水解可生成相应的醇,频哪醇和烯烃,其选择性不仅与反应时间和温度有关,而且还与羰基化合物的种类以及CeCl_3:LiNp:RCOR＇的摩尔比有关。初步研究了Ce~*作用下的酮和一些卤代烃的反应。     

Cerium masquerading as a group 4 element: synthesis,structure and computational characterisation of [CeCl(N(SiMe3)2)3

Oxidation of the three-coordinate cerium amide [Ce(N-(SiMe3)2)3] with TeCl4 in toluene solution yields purple, diamagnetic [CeCl(N(SiMe3)2)3], whose structure has been examined by X-ray crystallographic and computational methods.     

Formation and crystal structure of an unexpected inclusion complex of a metal-free phthalocyanine and oxalic acid

Treatment of 3-(2,4-dimethyl-3-pentyloxy)phthalonitrile (2) with CeCl3 in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in n-pentanol gives the corresponding metal-free phthalocyanine 3, which unexpectedly traps the oxalic acid in the crystal lattice forming a 1:1 inclusion complex.     

Thermodynamic stability of RECl3·xH2O (RE = Ce,Pr) determined by dynamic transpiration technique

Journal of Thermal Analysis and Calorimetry - In the present study, decomposition mechanism of CeCl3·xH2O(s) and PrCl3·xH2O(s) was investigated using thermogravimetry, differential...     

CeCl3·7H2O-SiO2： Catalyst promoted microwave assisted neat synthesis, antifungal and antioxidant activities of α-diaminophosphonates

CeCl₃·7H₂O supported on silica（CeCl₃·7H₂O-SiO₂） is used as a heterogeneous,efficient and recyclable catalyst for a three component one-pot reaction of an amine,aldehydes and diethyl phosphite to synthesizeα-diaminophosphonate derivatives under microwave irradiation exploiting neat reaction conditions.Tenα-diaminophosphonates（6a-j） of 4,4’-sulfonyldianiline（Dapsone）（3） were synthesized and structural elucidation was confirmed by spectral data.Antifungal and antioxidant activities were evaluated include minimum inhibitory concentrations and IC₅₀ values,respectively of the titled compounds.Compounds 6h,6i exhibited promising antioxidant activity at lower IC₅₀ values 53.7μg/mL, 53.2μg/mL,respectively as compared with standard IC₅₀ value 51.6μg/mL.     

Improved heteroatom nucleophilic addition to electron-poor alkenes promoted by CeCl3.7H2O/NaI system supported on alumina in solvent-free conditions

Conjugate addition of heteroatom nucleophiles to carbon-carbon double bonds conjugated with a strong electron-withdrawing group is one of the most important new bond-forming strategies in synthetic organic chemistry. Among the methods for these Michael additions, Lewis acids have shown the best promoter activity, and in particular, the use of reagents impregnated over inorganic supports is rapidly increased. With the increase of environmental consciousness in chemical research, the solvent-free Michael addition has attracted our attention. In continuation of our ongoing program to develop synthetic protocols utilizing cerium trichloride, we report an extension of the CeCl(3).7H(2)O/NaI combination supported under solvent-free conditions to promote heteroatom Michael addition. Using neutral alumina (Al(2)O(3)) as solid support permits us to circumvent some of the problems associated with the procedure where the inorganic support is silica gel. The CeCl(3).7H(2)O/NaI/Al(2)O(3) system works well for hetero-Michael additions utilizing weakly nucleophiles such as imidazoles and carbamates, and also the reaction proceeds with good yields in the case of Michael acceptors different from alpha,beta-unsaturated carbonyl compounds. An important synthetic application of this our methodology is the intramolecular aza-Michael reaction in producing 4-piperidinone derivatives, which are of interest as synthetic intermediates toward important classes of heterocycles.     

Unusual and unexpected reactivity of t-butyl dicarbonate (Boc2O) with alcohols in the presence of magnesium perchlorate. A new and general route to t-butyl ethers

[reaction: see text] A new mild method for protecting alcohols as t-butyl ethers is reported. The reaction proceeds with Mg(ClO4)2 and Boc2O and shows general applicability. The deprotection of t-butyl ethers has also been revisited. Preliminary results indicate the CeCl3 x 7H2O/NaI system is a very suitable catalyst for their removal.