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21.
Otero A Fernández-Baeza J Antiñolo A Carrillo-Hermosilla F Tejeda J Lara-Sánchez A Sánchez-Barba L Fernández-López M Rodríguez AM López-Solera I 《Inorganic chemistry》2002,41(20):5193-5202
The preparation of new "scorpionate" ligands in the form of the lithium derivatives [(Li(bdmpzdta)(H(2)O))(4)] (1) [bdmpzdta = bis(3,5-dimethylpyrazol-1-yl)dithioacetate], [Li(bdphpza)(H(2)O)(THF)] (2) [bdphpza = bis(3,5-diphenylpyrazol-1-yl)acetate], and [Li(bdphpzdta)(H(2)O)(THF)] (3) [bdphpzdta = bis(3,5-diphenylpyrazol-1-yl)dithioacetate] has been carried out. Furthermore, a series of titanium complexes has been prepared by reaction of TiCl(4)(THF)(2) with the lithium reagents [(Li(bdmpza)(H(2)O))(4)] (4) [bdmpza = bis(3,5-dimethylpyrazol-1-yl)acetate] and 1. Under the appropriate experimental conditions neutral complexes, namely [TiCl(3)(kappa(3)-bdmpza)] (5), [TiCl(3)(kappa(3)-bdmpzdta)] (6), and [TiCl(2)(kappa(2)-bdmpzdta)(2)] (7), and cationic complexes, namely [TiCl(2)(THF)(kappa(3)-bdmpza)]Cl (8) and [TiCl(2)(THF)(kappa(3)-bdmpzdta)]Cl (9), were isolated. Complexes 8 and 9 undergo an interesting nucleophilic THF ring-opening reaction to give the corresponding alkoxide-containing species [TiCl(2)(kappa(3)-bdmpza)(O(CH(2))(4)Cl)] (10) and [TiCl(2)(kappa(3)-bdmpzdta)(O(CH(2))(4)Cl)] (11). A family of alkoxide-containing complexes of general formulas [TiCl(2)(kappa(3)-bdmpza)(OR)] [R = Me (12); R = Et (14); R = (i)Pr (16); R = (t)Bu (18)] and [TiCl(2)(kappa(3)-bdmpzdta)(OR)] [R = Me (13); R = Et (15); R = (i)Pr (17)] was also prepared. The structures of these complexes have been determined by spectroscopic methods, and in addition, the X-ray crystal structures of 3, 7, 10, and 11 were also established. 相似文献
22.
de Farias RF de Souza JM de Melo JV Airoldi C 《Journal of colloid and interface science》1999,212(1):123-129
The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press. 相似文献
23.
Oxidation of (η5-C5H5)2MCl (M = Nb, Ta) with 1 mol of Cl2, Br2 or I2 gives (η5-C5H5)2MClX2 whereas the reaction with an excess of the halogen gives the cationic complexes [η5-C5H5)2MClX]+ X3? (X = Br, I). Similar oxidation of (η5-C5H5)2MCl2 with 0.5 mol of halogen gives (η5-C5H5)2MCl2X complexes, but if the halogen is used in excess cationic [η5-C5H5)2MCl2]+ X3? (X = Br, I; M = Ta and X = I, M = Nb) are obtained. All these complexes can also be obtained simultaneously by oxidizing (η5-C5H5)4M2Cl3, and the separation is fairly easy in most cases. Conductivity and IR and NMR data are discussed. 相似文献
24.
Fandos R Hernández C Otero A Rodríguez A Ruiz MJ Terreros P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(3):671-677
Titanium complexes with chelating alkoxide ligands [TiCp*(O(2)Bz)(OBzOH)] (1) and [TiCp*(Me)((OCH(2))(2)Py)] (2) were synthesised by reaction of [TiCp*Me(3)] (Cp*=eta(5)-C(5)Me(5)) with 2-hydroxybenzyl alcohol ((HO)(2)Bz) and 2,6-pyridinedimethanol ((HOCH(2))(2)Py), respectively. Complex 1 reacts with [(M(mu-OH)(cod))(2)] (M=Rh, Ir) to yield the early-late heterobimetallic complexes [TiCp*(O(2)Bz)(2)M(cod)] [M=Rh (3), Ir (4)]. Carbon monoxide readily replaces the COD ligand in 3 to give the rhodium dicarbonyl derivative [TiCp*(O(2)Bz)(2)Rh(CO)(2)] (5). Compound 2 reacts with [(M(mu-OH)(cod))(2)] (M=Rh, Ir) with protonolysis of a Tibond;Me bond to give [TiCp*((OCH(2))(2)Py)(mu-O)M(cod)] [M=Rh (6), Ir (7)]. The molecular structures of complexes 3, 5 and 7 were established by single-crystal X-ray diffraction studies. 相似文献
25.
It is known that full Peano Arithmetic does not have the jointembedding property(JEP). At the other extreme of the hierarchy,Open Induction also fails to have this property. We prove, using some conservation results about fragments ofarithmetic, that if T is a theoryconsistent with PA and T I (bounded existential parameter-freeinduction), then any two m dels of PA which jointly embed ina model of T also jointly embed in an elementary extension ofone of them. In particular, any fragment of PA extending I fails to have JEP. 相似文献
26.
Laurent Salvi Hélène Cattey Yves Mugnier Antonio Otero 《Journal of organometallic chemistry》2004,689(22):3473-3480
Electrochemical reduction of niobocene dichloride (η5-C5H4SiMe3)2NbCl21 formulated as in the presence of 3,4-diaminobenzoic acid yields to the complex [Nb(η5-C5H4SiMe3)2(κ2-O,O-OOC(C6H3)(NH2)2)] 3. When CN(2,6-Me2C6H3) formulated as xylylisonitrile (CNXylyl) is added to a complex 3 solution, a substitution reaction takes place to lead to the complex [Nb(η5-C5H4SiMe3)2(κ1-O-OOC(C6H3)(NH2)2)(CN(2,6-Me2C6H3)) 4 after 3 h. An alternative way to yield quantitatively and nearly instantaneously 4 consists in a previous oxidation of 3 in the presence of CNXylyl. Hence, we present here a new example of electron-transfer-catalyzed (ETC) ligand substitution of carboxylato niobocene complex induced by electrochemical oxidation. The structure of the complexes, the formation mechanism are described using electrochemical and spectroscopic data. Electrochemical simulation have been done to verify experimental results and to complete them with a kinetic study. 相似文献
27.
Sonia Dopico‐García Ana Ares‐Pernas Jorge Otero‐Canabal Mar Castro‐López José M. López‐Vilariño Victoria González‐Rodríguez María J. Abad‐López 《先进技术聚合物》2013,24(8):723-731
Nowadays, there is a growing availability of biodegradable industrial materials intended to food contact applications whose service life behavior needs to be further investigated. This article is focused on the degradation of two materials based on polylactic acid. The correlation between the rate of degradation and the amount of trapped degradation products was investigated applying three characterization techniques in parallel, namely rheology, high‐performance liquid chromatography (HPLC), and matrix‐assisted laser desorption/ionization (MALDI). The rate of degradation was studied through the evaluation of their rheological properties and calculation of the number of average molecular weights, and weight‐average molecular weights. Water‐soluble oligomers and lactic acid were quantified by HPLC‐ultraviolet. Changes in cyclic and linear oligomers were monitored by MALDI‐time‐of‐flight mass spectrometry. Specimens of 4‐mm thickness of each biopolymer were subjected to hydrolysis in deionized water up to 6 months at two temperatures, simulating service conditions of food packaging. The diminution in viscosity and consequently in molecular weight distribution (20–60%) showed the degradation of the molecular structure of both polylactic acids. The chain scission was followed through the increasing values of lactic acid and hydrolyzed oligomers (twofold to eightfold), and the predominant signal of the linear oligomers over the cyclic ones with aging. Rheology, HPLC, and MALDI showed to be complementary tools to better understand the changes in the molecular structure. The obtained results showed the necessity of adding suitable stabilizers for each particular food packaging application. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
28.
Aggregation‐induced emission (AIE) is a phenomenon where non‐luminescent compounds in solution become strongly luminescent in aggregate and solid phase. It provides a fertile ground for luminescent applications that has rapidly developed in the last 15 years. In this review, we focus on the contributions of theory and computations to understanding the molecular mechanism behind it. Starting from initial models, such as restriction of intramolecular rotations (RIR), and the calculation of non‐radiative rates with Fermi's golden rule (FGR), we center on studies of the global excited‐state potential energy surfaces that have provided the basis for the restricted access to a conical intersection (RACI) model. In this model, which has been shown to apply for a diverse group of AIEgens, the lack of fluorescence in solution comes from radiationless decay at a CI in solution that is hindered in the aggregate state. We also highlight how intermolecular interactions modulate the photophysics in the aggregate phase, in terms of fluorescence quantum yield and emission color. 相似文献
29.
Dr. María Jose Capitán Dr. Jesús Álvarez Dr. Yang Wang Dr. Roberto Otero Dr. Manuel Alcamí Prof. Fernando Martín Prof. Rodolfo Miranda 《Chemphyschem》2013,14(14):3294-3302
The structure and stability of adenine crystals and thin layers has been studied by using scanning tunneling microscopy, X‐ray diffraction, and density functional theory calculations. We have found that adenine crystals can be grown in two phases that are energetically quasi‐degenerate, the structure of which can be described as a pile‐up of 2D adenine planes. In each plane, the structure can be described as an aggregation of adenine dimers. Under certain conditions, kinetic effects can favor the growth of the less stable phase. These results have been used to understand the growth of adenine thin films on gold under ultra‐high vacuum conditions. We have found that the grown phase corresponds to the α‐phase, which is composed of stacked prochiral planes. In this way, the adenine nanocrystals exhibit a surface that is enantiopure. These results could open new insight into the applications of adenine in biological, medical, and enantioselective or pharmaceutical fields. 相似文献
30.
Significant nonlinear‐optical switching capacity in atomic clusters built from silicon and lithium: A combined ab initio and density functional study 下载免费PDF全文
Panaghiotis Karamanis Nicolás Otero Claude Pouchan Juan José Torres William Tiznado Aggelos Avramopoulos Manthos G. Papadopoulos 《Journal of computational chemistry》2014,35(11):829-838
Starting from a hypothetical but fundamental charge/discharge sequence, the topic of nonlinear optical switching in atomic clusters built from silicon and alkali metals is opened up. The outcomes presented in this work, obtained with ab initio methods of exceptional predictive capabilities, offer strong evidences that sizable hyperpolarizability contrasts between neutral and charged alkali metal doped cluster forms might be simultaneously accomplished. The observed switching procedure involves redox polyatomic clusters formed by Si atoms. These centers function as electron acceptors at the ground state and as electron donors at the excited states facilitating low energy charge transfer transitions upon electronic excitation. © 2014 Wiley Periodicals, Inc. 相似文献