bluuebunny/crossref_metadata_2025_split huggingface dataset:
Periodic Table: Trends in the Properties of the Elements
Authors: Wulfsberg G. P. 
Published: March 2006

Abstract

The article gives examples of trends in properties of the elements, their ions, and their compounds, which can usefully be examined from the perspective of the periodic table as a whole, rather than by looking at one group of elements (or even individual elements) at a time. The properties discussed are those of great interest not only to inorganic chemists but also to research workers in allied fields, such as the other branches of chemistry, medicinal chemistry, environmental science, agricultural and geochemistry, industrial chemistry and safety, metallurgy, materials science, and surface chemistry. These trends can be organized, explained, and predicted on the basis of a small set of parameters of the elements and their ions, most notably the sizes of the ions, their charges (or oxidation numbers), and the Pauling electronegativities of the elements. Trends are emphasized in acid–base reactivity, precipitation and solubility trends, coordination chemistry, oxidation–reduction chemistry, and physical properties of the elements and their compounds. Much acid–base and precipitation chemistry can be predicted after calculating the p
K
a
values of cations and the p
K
b
values of anions, or simply predicting to which of the six acidity and basicity categories an ion belongs. Generally very useful in coordination chemistry are the chelate and macrocyclic effects and the Hard–Soft Acid–Base (HSAB) Principle. Oxidation–reduction chemistry of the elements can be summarized graphically in the form of Pourbaix diagrams or by redox predominance diagrams where the pH is set at the standard pH value of zero. Among physical properties, perhaps the most important for applications in materials science is whether a compound that might be synthesized is a solid with an extended structure; methods are given for predicting this on the basis of the radius ratios of the cations and anions (at least formally) contained in the compound. One physical property, metallic conduction, is discussed in further detail. As an example of chemical properties, trends in the acidity and basicity of oxides of the elements are discussed.
Polyphosphazenes
Authors: Allcock Harry R. 
Published: March 2006

Abstract
Polyphosphazenes comprise the largest class of inorganic polymers. During the past 10 years, new synthetic developments have arisen that allow carefully tailored macromolecules to be assembled with precise chain lengths and with access to star geometries and a range of hybrid phosphazene‐organic polymer systems. This has stimulated research in the use of polyphosphazenes in biomedicine, optoelectronics (photonics), lithium battery technology, and fuel cell membranes, as well as in new elastomers and hydrogels.
Quasicrystals
Authors: King R. Bruce 
Published: March 2006

AbstractQuasicrystals are solid materials exhibiting diffraction patterns with apparently sharp spots containing symmetry axes such as fivefold or eightfold axes, which are incompatible with the three‐dimensional periodicity associated with crystal lattices. Many such materials are aluminum alloys that exhibit diffraction patterns with fivefold symmetry axes; such materials are called icosahedral quasicrystals. The location of atoms in quasicrystals requires the use of six‐dimensional crystallography. However, a polyhedral shell structure using a number of polyhedra of icosahedral symmetry provides a three‐dimensional model for the structure of many icosahedral quasicrystals.
Semiconductors
Authors: Stanton Colby E. , Nguyen SonBinh T. , Kesselman Janet M. , Laibinis Paul E. , Lewis Nathan S. 
Published: March 2006

Abstract
The structural, electronic, optical, and electrical properties of semiconductors are treated within a common framework. The bonding in the lattice determines the band structure of the solid, which is used to describe the chemical, optical, and electrical properties of the semiconductor. These concepts enable this process to be understood from a qualitative, chemically based viewpoint.
Technetium: Organometallic ChemistryBased in part on the article Technetium: Organometallic Chemistry by Ronald J. Clark which appeared in the
Encyclopedia of Inorganic Chemistry, First Edition
.
Authors: Rochon Fernande D. 
Published: March 2006

Abstract

The chemistry of organometallic technetium compounds is discussed along with its application in the field of nuclear medicine. Several
99m
Tc radiopharmaceuticals are presently used in hospitals using a
99
Mo−
99m
Tc generator to prepare the starting material [
99m
TcO
4
]
−
. The isotope
99m
Tc is a γ‐ray emitter. The most common organometallic radiopharmaceutical is [Tc(MIBI)
6
]
+
, where MIBI is an isonitrile ligand.
99m
Tc can be produced only at the tracer level and it disintegrates to the longer life isotope
99
Tc, which has a half‐life of 2.12 × 10
5
years. The chemistry of technetium has been studied with the latter isotope, which is commercially available. But it emits weak β
−
particles and special precautions must be taken in the laboratories in order to avoid health problems.

Most of the publications in the literature on organometallic Tc compounds contain the ligands CO, isonitriles or the cyclopentadienyl ion. These π‐accepting ligands usually bind to Tc in a low oxidation states. Tc‐CO compounds are the ones who have been most studied. Binary compounds and a great variety of mixed‐ligands complexes are discussed. The new complex ion [Tc(CO)
3
(H
2
O)
3
]
+
is particularly important, since a kit was recently developed for its preparation. It should open a new field for the development of
99m
Tc radiopharmaceuticals. It can bind to biomolecules like proteins, peptides, and antibodies which have very specific targets.

Several Tc‐cyclopentadienyl complexes have the sandwich or the piano stool structures. The arene compounds should have similar structures, but the latters have not been much studied yet. No Tc‐arene compound seem to have been characterized by crystallographic methods yet. But more recently, interest in the arene complexes has increased because of its potential use in nuclear medicine. Isonitriles or isocyanides and cyanide ligands are bonded to Tc through the C atom. A few crystal structures on mixed‐ligand isonitrile Tc complexes were determined and the segment TcCNC is linear. Fewer cyanide Tc compounds were studied. Finally a few Tc‐alkyl compounds have been reported.
Water &
O
‐Donor Ligands
Authors: Ogden Mark I. , Beer Paul D. 
Published: March 2006

Abstract

The chemistry of a range of O‐donor ligands is described, with an emphasis on the various ligand coordination modes and different structural types of the complexes formed. Water as a ligand is discussed along with the related hydroxide and oxide species. The structure, preparation, and reactions of alkoxide and aryloxide complexes are described. Similar coverage is provided for the diketone ligands. The rich variety of coordination modes of oxoanions, carboxylates, and related ligands, is emphasized. Complexation and structural chemistry of macrocyclic O‐donor ligands are discussed, particularly focusing on crown ether and calixarene metal complexes. The final section provides an overview of the chemistry of other commonly encountered η
1
O‐donor ligands.
Alkaline Earth Metals: Organometallic Chemistry
Authors: Alexander Jacob S. , Guino‐o Marites , Zuniga Maria Felisa , Hahn Roger C. , Ruhlandt‐Senge Karin 
Published: March 2006

Abstract
The organometallic chemistry of the alkaline earth metals has undergone a renaissance during the last decade with exciting novel uses of the organomagnesium reagents in synthetic chemistry to significantly extend the utility of these well‐developed reagents. With the development of the organometallic chemistry of the heavier metals significantly lagging behind, and past work mainly focusing on and establishing π‐bonded metal–ligand systems, intense research efforts during the last decade have contributed significantly to expand the understanding of the organometallic compounds of these metals, establishing σ‐bonded organometallic compounds for the heavy alkaline earth metals. This improved insight did not only provide the basis for a more detailed understanding of the metal–ligand bonding characteristics, but also paved the way towards the successful applications of the compounds as polymerization initiators and in organic synthetic chemistry. This article summarizes some of the recent, exciting developments in regards to alkaline earth organometallics.
Luminescence Behavior & Photochemistry of Organotransition Metal Compounds
Authors: Yam Vivian Wing‐Wah , Lo Kenneth Kam‐Wing 
Published: March 2006

AbstractIn this article, the luminescence and photochemical properties of a selection of organotransition metal compounds are reviewed and discussed. The examples are classified according to the identity of the carbon‐containing ligands, which include the carbonyl, isocyanide, cyanide, alkynyl, alkenyl, arene, aryl, alkylidene, alkylidyne, cyclometalating, and alkyl ligands. The luminescence and photochemistry of selected tungsten, molybdenum, and rhenium carbonyl compounds are described in this article, followed by some examples with the analogous isocyanide and cyanide ligands. The luminescence properties and potential applications of these systems are discussed. Transition metal complexes containing alkynyl ligands display a very wide structural diversity and catalytic properties, and many systems also show intriguing photoluminescence properties, especially those of rhenium(I), platinum(II), palladium(II), and the coinage metals. Studies focused on the photophysical studies and the excited‐state chemistry of selected alkynyl systems and related alkenyl, arene, and aryl complexes are outlined and discussed. Luminescent metal–carbon multiple bonded systems including the alkylidene and alkylidyne compounds have received relatively little attention, and examples have been confined to the complexes of molybdenum and tungsten. However, much effort has recently been devoted to exploring the interesting emission properties of alkylidene and alkylidyne systems with other metal centers such as rhenium, ruthenium, osmium, platinum, and coinage metals, which are outlined in this article. Some recent examples in the areas of cyclometalated complexes, especially those of rhodium(III), iridium(III), platinum(II), and gold(III) centers are highlighted in this article as many examples display impressive photophysical and photochemical behavior. Metal alkyl systems represent a special class of luminescent organometallic system due to their strong σ‐donating properties of the alkyl ligands, and the photophysical and excited‐state properties of some selected examples are described. Finally, luminescent organotransition metal compounds with application potentials in the development of new materials, photodevices, and sensory systems are summarized in various parts of this article.
Metal‐Based Imaging Agents
Authors: Francesconi Lynn C. , Cantorias Melchor V. , Howell Robertha C. 
Published: March 2006

Abstract

Radiopharmaceuticals are drugs that contain a radionuclide and are routinely used for diagnosis and treatment of disease. This review discusses imaging agents that are useful for diagnosis using Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET). Moreover, this entry focuses on the growing class of metal‐based imaging agents, wherein the radionuclide is a transition metal or posttransition metal. The most widely used radionuclide for radiopharmaceuticals is technetium‐99m,
99m
Tc, owing its widespread availability from the parent–daughter generator and its excellent physical properties for imaging. The radionuclides
67
Ga,
111
In,
210
Tl,
57
Co, and
51
Cr are used in the clinic as well. There are a number of radioisotopes, including
64
Cu,
67
Cu,
68
Ga, that show promise for diagnostic purposes. An increased understanding of the coordination chemistry of
99m
Tc and other radiometals resulted in first‐generation metal‐essential imaging agents. This understanding of coordination chemistry is responsible for the introduction and development of targeted receptor‐specific agents, many of which are in clinical trials and some of which are on the market.
Carbene Complexes
Authors: Crabtree Robert H. 
Published: March 2006

Abstract
The synthesis, structure, reactions, and applications of carbenes are discussed. Fischer and Schrock carbenes are distinguished. N‐heterocyclic carbenes (NHCs) are considered as a class of Fischer carbenes with promise as spectator ligands in homogeneous catalysis. Nucleophilic attack on carbonyls and alpha elimination are noted as leading pathways leading to Fischer and Schrock carbenes, respectively. Criteria are discussed for characterization of carbenes, notably nuclear magnetic resonance (NMR) spectroscopy. The Grubbs metathesis catalyst and alkene metathesis catalysis are also mentioned. Bridging carbenes and carbynes are briefly considered.
Alkane Carbon–Hydrogen Bond Activation
Authors: Crabtree Robert H. 
Published: March 2006

AbstractThe title topic is reviewed with attention to alkane complexes, Shilov chemistry, alkane functionalization, Fenton reagents, oxidative addition pathways, sigma bond metathesis pathways, and surface‐bound reagents. Methane to methanol chemistry is discussed and attempts to commercialize the reaction are described in connection with Periana systems. Some organic synthetic applications are also covered. Future challenges are posed.
Synthesis of 3‐Substituted Furans by Hydroformylation
Authors: Nanayakkara Perli , Alper Howard 
Published: March 2006

AbstractA simple and novel method for the synthesis of 3‐substituted furans by the hydroformylation of substituted propargylic alcohols is described using rhodium acetate and triphenylphosphine in dichloromethane. The hydroformylation reaction proceeds in a regioselective manner under mild reaction conditions. This novel methodology is versatile and can be applied to the synthesis of a variety of 3‐aryl‐substituted furans.
Layered Double Hydroxides‐Supported Diisopropylamide: Synthesis, Characterization and Application in Organic Reactions
Authors: Kantam M. Lakshmi , Ravindra A. , Reddy Ch. Venkat , Sreedhar B. , Choudary B. M. 
Published: March 2006

AbstractThe layered double hydroxides‐supported diisopropylamide (LDH‐DA) catalyst is found to be an efficient and selective solid base for aldol, Knoevenagel, Henry, Michael, transesterification and epoxidation reactions under liquid phase conditions. LDH‐DA is synthesized by the interaction of lithium diisopropylamide with LDH‐NO3 (as‐synthesized) and calcined LDH‐NO3. The LDH‐DA (Mg/Al, 3/1) and their precursors are well characterized by using various instrumental techniques such as FT‐IR, TGA and DTA, powder XRD, solid state 27Al MAS NMR spectroscopy, SEM and XPS (ESCA).
Planar‐ and Central‐Chiral N,O‐[2.2]Paracyclophane Ligands: Non‐Linear‐Like Effects and Activity
Authors: Lauterwasser Frank , Vanderheiden Sylvia , Bräse Stefan 
Published: March 2006

AbstractThe non‐linear‐like effect (NLLE), activity, temperature dependence, and kinetics of hydroxy[2.2]paracyclophane ketimine ligands have been investigated with the 1,2‐addition reaction of diethylzinc to cyclohexanecarbaldehyde. A linear correlation between the enantiomeric excess of AHPC ketimine ligands bearing a phenylethyl side group and the product was observed with 0.5 mol % of catalyst loading. On increasing the catalyst loading to 4 mol %, a precipitate of the inactive heterochiral species was formed and resulted in a positive non‐linear‐like effect. The enantiomeric ratio was found to have linear temperature dependence.
A Bimetallic Ruthenium Complex as a Catalyst Precursor for the Atom Transfer Radical Polymerization of Methacrylates at Ambient Temperature
Authors: Haas Michel , Solari Euro , Nguyen Quoc T. , Gautier Sébastien , Scopelliti Rosario , Severin Kay 
Published: March 2006

AbstractThe bimetallic ruthenium complex [(1,3,5‐i‐Pr3C6H3)Ru(μ‐Cl)3RuCl(C2H4)(PCy3)] has been synthesized by reaction of [(1,3,5‐i‐Pr3C6H3)RuCl2)]2 with one equivalent of PCy3 in the presence of ethylene. It can be used as a catalyst precursor for the controlled atom transfer radical polymerization of methacrylates at 35 °C. The resulting polymers show low polydispersities.
Enantioselective Ring Opening of Epoxides with Cyanide Catalysed by Halohydrin Dehalogenases: A New Approach to Non‐Racemic β‐Hydroxy Nitriles
Authors: Elenkov Maja Majerić , Hauer Bernhard , Janssen Dick B. 
Published: March 2006

AbstractHalohydrin dehalogenases (HheA, HheB and HheC) were found to efficiently catalyse a carbon‐carbon bond forming reaction between terminal aliphatic epoxides and cyanide, yielding β‐hydroxy nitriles. With all three enzymes nucleophilic ring opening of epoxides proceeds with high regioselectivity to the β‐carbon atom. Activity, enantioselectivity and enantiopreference depend on the type of enzyme and the substrate structure. HheC was found to be the most selective among the tested enzymes. The enantioselectivity toward monosubstituted epoxides varies from moderate to high (E=5–106), while resolution of 2,2‐disubstituted epoxides proceeds with very high enantioselectivity (E=141 and 200). The results show that halohydrin dehalogenases may become attractive catalysts for the facile preparation of enantiopure β‐hydroxy nitriles from racemic epoxides.
Promiscuous Acylases‐Catalyzed Markovnikov Addition of N‐Heterocycles to Vinyl Esters in Organic Media
Authors: Wu Wei‐Bo , Xu Jian‐Ming , Wu Qi , Lv De‐Shui , Lin Xian‐Fu 
Published: March 2006

AbstractThree acylases, including D‐aminoacylase from Escherichia coli, acylase “Amano” from Aspergillus oryzae and immobilized penicillin G acylase from Escherichia coli have been found to possess novel activity to catalyze the Markovnikov addition reaction of N‐heterocycles to vinyl esters. The aza‐Markovnikov addition reactions of 4‐nitroimidazle to vinyl acetate catalyzed by D‐aminoacylase, acylase “Amano” and immobilized penicillin G acylase were up to 1260‐fold, 720‐fold and 320‐fold faster than the respective non‐enzymatic reaction. Some control experiments have been designed to demonstrate the catalytic specificity of acylases. Under the catalysis of these promiscuous acylases, a number of N‐heterocycles, including some pentacyclic N‐heterocycles, pyrimidines and purines, were successfully added to a series of vinyl esters in moderate to excellent yields to prepare N‐heterocycle derivatives. The acylase‐catalyzed Markovnikov addition reaction has provided a new strategy to perform the Markovnikov addition and expanded the application of biocatalysts.
The First Air‐Stable and Efficient Nucleophilic Trialkylphosphine Organocatalyst for the Baylis–Hillman Reaction
Authors: He Zhengrong , Tang Xiaofang , Chen Yaoming , He Zhengjie 
Published: March 2006

Abstract1,3,5,‐Triaza‐7‐phosphaadamantane (PTA) is first reported to be a convenient and efficient nucleophilic trialkylphosphine organocatalyst for the Baylis–Hillman reaction. Thus, under the mediation of 15–20 mol % of PTA and practical conditions, both aromatic and aliphatic aldehydes react with the activated alkenes like acrylates and methyl vinyl ketone to afford the corresponding adducts in fair to excellent yields.
Alkylation of Arenes with Benzylic and Propargylic Alcohols – Classical versus Fancy Catalysts
Authors: Liu Jianhui , Muth Enrico , Flörke Ulrich , Henkel Gerald , Merz Klaus , Sauvageau Janelle , Schwake Erik , Dyker Gerald 
Published: March 2006

AbstractGold chloride and BF3⋅etherate were tested as Friedel–Crafts catalysts in the propargylation of electron‐rich arenes: differences in reactivity of the catalysts can be used to achieve high selectivity either for monoalkylation or for multiple alkylation products. In the case of a macrocyclization towards a heterocalixarene, gold catalysts exhibited a pronounced selectivity, whereas p‐toluenesulfonic acid as catalyst opened up a competing pathway to a structural isomer.
Contribution of peptides to multiple sclerosis research
Authors: Alcaro Maria Claudia , Papini Anna Maria 
Published: March 2006

AbstractMultiple sclerosis (MS) is an autoimmune disease associated with chronic inflammatory demyelination of the central nervous system in genetically susceptible individuals. Because of the disease complexity and heterogeneity, its pathogenesis remains unknown despite extensive research efforts, and specific effective treatments have not yet been developed. Peptide‐based research has been important in attempts to unravel particular aspects of this complex disease, including the characterization of the different molecular mechanisms of MS, with the goal of providing useful products for immune‐mediated therapies. In fact, in the past decade, peptide‐based research has been predominant in research aimed to identify and/or develop target antigens as synthetic probes for specific biomarkers as well as innovative immunomodulating therapies. This review presents an overview of the contributions of peptide science to MS research and discusses future directions of peptide‐based investigations. © 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 84: 349–367, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Meta-analysis of observational studies of ileorectal versus ileal pouch–anal anastomosis for familial adenomatous polyposis
Authors: Aziz O , Athanasiou T , Fazio V W , Nicholls R J , Darzi A W , Church J , Phillips R K S , Tekkis P P 
Published: March 2006

Abstract

Background
Surgery for familial adenomatous polyposis (FAP) aims to minimize cancer risk while providing good functional outcome. Colectomy with ileorectal anastomosis and proctocolectomy with ileal pouch–anal anastomosis both offer this, but there is no clear consensus about which is better.

Methods
This is a meta-analysis of comparative studies published between 1991 and 2003 reporting early and late postoperative adverse events, functional outcomes and quality of life.

Results
Twelve studies containing 1002 patients (53·4 per cent ileal pouch, 46·6 per cent ileorectal anastomosis) were identified. Bowel frequency (weighted mean difference 1·62 (95 per cent confidence interval (c.i.) 1·05 to 2·20)), night defaecation (odds ratio (OR) 6·64 (95 per cent c.i. 2·99 to 14·74)) and use of incontinence pads (OR 2·72 (95 per cent c.i. 1·02 to 7·23)) were significantly less in the ileorectal group, although faecal urgency was reduced with the ileal pouch (odds ratio 0·43 (95 per cent c.i. 0·23 to 0·80)). Reoperation within 30 days was more common after ileal pouch construction (23·4 versus 11·6 per cent; OR 2·11 (95 per cent c.i. 1·21 to 3·70)). There was no significant difference between the techniques in terms of sexual dysfunction, dietary restriction, or postoperative complications. Rectal cancer was a diagnosis only in the ileorectal group (5·5 per cent).

Conclusion
Ileal pouch and ileorectal anastomoses have individual merits. Further research is needed to determine which most benefits patients with FAP.
Optimisation of the treatment conditions of cocoa butter in order to reduce non‐quality
Authors: Assidjo Emmanuel , Yao Benjamin , Akou Etienne , Ado Gossan 
Published: March 2006

AbstractThe interest of the use of the experimental designs for the improvement of an industrial process in a real context of production was highlighted by the optimisation of the demucilagination and deodorisation conditions of the cocoa butter using complete factorial designs. The study carried out enabled to obtain a reduction of non‐conformity of the final product (cocoa butter) of 28% in times of intensive production to less than 5%. The models obtained for each operation were validated in real industrial context. Copyright © 2006 John Wiley & Sons, Ltd.