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Showing papers in "Chemical Society Reviews in 2004"


Journal ArticleDOI
TL;DR: Practical guidelines for the preparation and use of different Schiff base metal complexes in the field of catalytic transformations are discussed in this tutorial review.
Abstract: Schiff base ligands are considered “privileged ligands” because they are easily prepared by the condensation between aldehydes and imines. Stereogenic centres or other elements of chirality (planes, axes) can be introduced in the synthetic design. Schiff base ligands are able to coordinate many different metals, and to stabilize them in various oxidation states, enabling the use of Schiff base metal complexes for a large variety of useful catalytic transformations. Practical guidelines for the preparation and use of different Schiff base metal complexes in the field of catalytic transformations are discussed in this tutorial review.

1,642 citations


Journal ArticleDOI
TL;DR: The tutorial review presented herein describes developments in diarylethene-based molecular switches made in the last three years and includes the synthetic aspects of diaryle thene photochromic compounds, which are important issues and neglected in most previous reviews.
Abstract: Organic photochromic materials have received considerable attention because of their potential for photonic applications, especially for fast and high density data storage. In 2000, Chemical Reviews published a special issue on photochromic materials including a review about the properties and applications of diarylethene photochromic compounds. Since then much impressive progress has been made in this area. Various new diarylethene derivatives have been prepared and examined. The tutorial review presented herein describes developments in diarylethene-based molecular switches made in the last three years. In addition, the synthetic aspects of diarylethene photochromic compounds, which are important issues and neglected in most previous reviews, have been included.

1,411 citations


Journal ArticleDOI
TL;DR: This tutorial review focuses on the living atom transfer radical polymerization (ATRP) system, and in this tutorial review a particular focus is given to examples of this technique.
Abstract: Polymer brushes produced by controlled surface-initiated polymerization provide a route to surfaces coated with well-defined thin polymer films that are covalently bound to the substrate. All of the major controlled polymerization techniques have been applied to the synthesis of polymer brushes and examples of each are presented here. Many examples of brush synthesis in the literature have used the living atom transfer radical polymerization (ATRP) system, and in this tutorial review a particular focus is given to examples of this technique.

1,242 citations


Journal ArticleDOI
TL;DR: Dendrimers are versatile, derivatisable, well-defined, compartmentalised chemical polymers with sizes and physicochemical properties resembling those of biomolecules e.g. proteins that may be used as drugs for antibacterial and antiviral treatment and have found use as antitumor agents.
Abstract: Dendrimers are versatile, derivatisable, well-defined, compartmentalised chemical polymers with sizes and physicochemical properties resembling those of biomolecules e.g. proteins. The present critical review (citing 158 references) briefly describes dendrimer design, nomenclature and divergent/convergent dendrimer synthesis. The characteristic physicochemical features of dendrimers are highlighted, showing the effect of solvent pH and polarity on their spatial structure. The use of dendrimers in biological systems are reviewed, with emphasis on the biocompatibility of dendrimers, such as in vitro and in vivo cytotoxicity, as well as biopermeability, biostability and immunogenicity. The review deals with numerous applications of dendrimers as tools for efficient multivalent presentation of biological ligands in biospecific recognition, inhibition and targeting. Dendrimers may be used as drugs for antibacterial and antiviral treatment and have found use as antitumor agents. The review highlights the use of dendrimers as drug or gene delivery devices in e.g. anticancer therapy, and the design of different host–guest binding motifs directed towards medical applications is described. Other specific examples are the use of dendrimers as ‘glycocarriers’ for the controlled multimeric presentation of biologically relevant carbohydrate moieties which are useful for targeting modified tissue in malignant diseases for diagnostic and therapeutic purposes. Finally, the use of specific types of dendrimers as scaffolds for presenting vaccine antigens, especially peptides, for use in vaccines is presented.

1,090 citations


Journal ArticleDOI
Chul Ho Jun1
TL;DR: This tutorial review deals with recent developments in the activation of C-C bonds in organic molecules that have been catalyzed by transition metal complexes and the strategies and tactics for C-B bond activation will be explained.
Abstract: This tutorial review deals with recent developments in the activation of C–C bonds in organic molecules that have been catalyzed by transition metal complexes. Many chemists have devised a variety of strategies for C–C bond activation and significant progress has been made in this field over the past few decades. However, there remain only a few examples of the catalytic activation of C–C bonds, in spite of the potential use in organic synthesis, and most of the previously published reviews have dwelt mainly on the stoichiometric reactions. Consequently, this review will focus mainly on the catalytic reaction of C–C bond cleavage by homogeneous transition metal catalysts. The contents include cleavage of C–C bonds in strained and unstrained molecules, and cleavage of multiple C–C bonds such as CC triple bonds in alkynes. Multiple bond metathesis and heterogeneous systems are beyond the scope of this review, though they are also fascinating areas of C–C bond activation. In this review, the strategies and tactics for C–C bond activation will be explained.

796 citations


Journal ArticleDOI
TL;DR: Two novel structural concepts have emerged during the past two years which have led literally to an explosion of the field of chiral NHC catalysts for stereoselective transformations in organic synthesis.
Abstract: In recent years, N-heterocyclic carbenes (NHC) have proved to be a versatile class of spectator ligands in homogeneous catalysis. Being robust anchoring functions for late transition metals, their ligand donor capacity and their molecular shape is readily modified by variation of the substituents at the N-atoms and the structure of the cyclic backbone. After the first attempts to use chiral NHC ligands in asymmetric catalysis in the late 1990's, which initially met with limited success, several novel structural concepts have emerged during the past two years which have led literally to an explosion of the field. With a significant number of highly selective chiral catalysts based on chiral NHCs having been reported very recently, several general trends in the design of new NHC-containing molecular catalysts for stereoselective transformations in organic synthesis emerge.

776 citations


Journal ArticleDOI
TL;DR: This critical review describes recent developments in the field of supramolecular chemistry of terpyridine-metal complexes and places a special emphasis upon the properties of functional systems.
Abstract: This critical review describes recent developments in the field of supramolecular chemistry of terpyridine–metal complexes. The synthesis and characteristics of single as well as multiple homo- and heterometallic complexes is discussed. Furthermore, complexes containing fullerenes, biological building blocks, extended aggregates of different architectures as well as rings are presented. A special emphasis is placed upon the properties (e.g. redox properties, luminescence etc.) of functional systems. Potential applications in optical nano-devices, molecular storage units, molecular switches and solar cells are discussed.

681 citations


Journal ArticleDOI
TL;DR: Two classes of compounds will be discussed: those based upon molecules or ions linked into networks via noncovalent interactions and those (coordination polymers) in which metal centres are linked using coordination bonds through bridging ligands into extended networks.
Abstract: The design and synthesis of crystalline materials through the self-assembly of molecular building blocks and the pursuit of functional materials based upon this approach are usually classified under the banner Crystal Engineering. The field is interdisciplinary in nature involving synthetic, materials, structural and theoretical chemists. There are strong ties to modern crystallography which can offer rapid and accurate structure determination and, in particular, insight into molecular and intermolecular geometries. Illustrative examples that chart the development field and provide an assessment of the current state of the art will be reviewed with an emphasis on inorganic chemistry. Broadly speaking, two classes of compounds will be discussed: those based upon molecules or ions linked into networks via noncovalent interactions and those (coordination polymers) in which metal centres are linked using coordination bonds through bridging ligands into extended networks.

662 citations


Journal ArticleDOI
TL;DR: This tutorial review covers the different methodologies for immobilisation, including: adsorption, encapsulation, tethering using a covalent bond and electrostatic interaction and is aimed at both researchers new to the field and those with a wider interest in the immobilisation of homogeneous catalysts.
Abstract: Enantioselective formation of C–H, C–C, C–O and C–N bonds has been extensively studied using homogeneous asymmetric catalysts for many years. However, these catalysts have yet to make a significant impact in the industrial synthesis of fine chemicals. A central reason is that homogeneous asymmetric catalyst design requires relatively bulky ligands and catalyst re-use through recovery and recycle often causes problems. One mechanism to overcome this problem is to immobilise the asymmetric catalyst onto a support and the resulting heterogeneous asymmetric catalyst can, in principle, be readily re-used. This tutorial review covers the different methodologies for immobilisation, including: adsorption, encapsulation, tethering using a covalent bond and electrostatic interaction and is aimed at both researchers new to the field and those with a wider interest in the immobilisation of homogeneous catalysts. Most importantly, recent studies will be highlighted that demonstrate that immobilised catalysts can give higher enantioselection when compared with their non-immobilised counterparts and the question of how high enantioselection can be achieved is addressed.

540 citations


Journal ArticleDOI
TL;DR: This tutorial review describes in a brief historical perspective the most important organic compounds that exhibit photochromism in the crystalline state since its discovery in 1867 up to now and considers in detail Schiff bases of salicylaldehyde with amines (anils).
Abstract: This tutorial review describes in a brief historical perspective the most important organic compounds that exhibit photochromism in the crystalline state since its discovery in 1867 up to now and considers in detail Schiff bases of salicylaldehyde with amines (anils). The latter comprise a chemical system undergoing hydrogen-atom tautomerism between enol and keto forms and show the phenomena of solid state photochromism and thermochromism. The system has been investigated extensively. Thus it has been shown that the photochromic property is a characteristic of the molecules but their chromobehaviour is influenced by the crystal structure of the compounds. Anils, apart from their fundamental interest, have potential for various applications.

520 citations


Journal ArticleDOI
Ji Min Lee1, Youngim Na1, Hoon Han1, Sukbok Chang1
TL;DR: One-pot co-catalyst systems are covered in this tutorial review and cooperative catalytic actions on both substrates by suitable catalysts proceed in a substrate-selective manner followed by the subsequent coupling of the two activated adducts providing the desired products.
Abstract: One-pot co-catalyst systems are covered in this tutorial review. It is divided into three sections according to the reaction types: i) one catalyst performs a desired reaction as the second catalyst restores the first catalytic species back into its original state for the next catalytic cycles, ii) two catalysts carry out sequential organic transformations, in which the first step is carried out by one catalyst to afford certain intermediates being to be subjected to the second catalyst for the next step, and iii) cooperative catalytic actions on both substrates by suitable catalysts proceed in a substrate-selective manner followed by the subsequent coupling of the two activated adducts providing the desired products.

Journal ArticleDOI
TL;DR: A critical review of the synthetic routes that have been applied to the synthesis of unsymmetrical ferrocene ligands, along with a systematic survey of the applications of these ligands in homogeneous catalysis is provided.
Abstract: Interest in the chemistry of ferrocene remains intense, largely due to applications within catalysis. New synthetic routes to unsymmetrical ferrocene ligands have provided another facet to this area, as substituents can be designed to be electronically- and/or sterically-distinct in order to affect the environment around the catalytically-active metal centre. This critical review provides a concise summary of the synthetic routes that have been applied to the synthesis of unsymmetrical ferrocene ligands, along with a systematic survey of the applications of these ligands in homogeneous catalysis. The aim is to help the reader select a suitable ferrocenediyl ligand for a particular synthetic application, and in the synthesis of ligands that require particular structural and/or electronic features. (186 references.)

Journal ArticleDOI
TL;DR: Metallosupramolecular squares have been successfully evolved over the past years as versatile substitutes of the conventional organic macrocycles owing to the development of reliable synthetic protocols and abundant structural variability (metals and ligands) as discussed by the authors.
Abstract: Metallosupramolecular squares have been successfully evolved over the past years as versatile substitutes of the conventional organic macrocycles owing to the development of reliable synthetic protocols and abundant structural variability (metals and ligands). In this review we have presented the fundamental aspects of metallosupramolecular squares such as the strategies for their construction (self-assembly vs. kinetically controlled macrocyclization) and characterization. The major emphasis of this tutorial review lies on the function of metallosupramolecular squares. Thus, the introduction of functionality into these systems has been discussed in detail by highlighting the recent progress toward application in various fields, including molecular recognition, enantioselective sensing, photoluminescence, redox activity and electrochemical sensing, and homogeneous catalysis.

Journal ArticleDOI
TL;DR: This overview traces the current physico-chemical understanding of the evolution of material from target ablation through to the deposited film, addressing the initial laser-target interactions by which solid material enters the gas phase.
Abstract: Pulsed laser ablation is a simple, but versatile, experimental method that finds use as a means of patterning a very diverse range of materials, and in wide areas of thin film deposition and multi-layer research. Superficially, at least, the technique is conceptually simple also, but this apparent simplicity hides a wealth of fascinating, and still incompletely understood, chemical physics. This overview traces our current physico-chemical understanding of the evolution of material from target ablation through to the deposited film, addressing the initial laser–target interactions by which solid material enters the gas phase, the processing and propagation of material in the plume of ejected material, and the eventual accommodation of gas phase species onto the substrate that is to be coated. It is intended that this Review be of interest both to materials scientists interested in thin film growth, and to chemical physicists whose primary interest is with more fundamental aspects of the processes of pulsed laser ablation and deposition.

Journal ArticleDOI
TL;DR: Both chiral metal complexes and small chiral organic molecules have been found to catalyse the direct aldol addition of unmodified ketones to aldehydes with relatively high chemical and stereochemical efficiency.
Abstract: Control of stereochemistry during aldol addition reactions has attracted considerable interest over the years as the aldol reaction is one of the most fundamental tools for the construction of new carbon–carbon bonds. Several strategies have been implemented whereby eventually any single possible stereoisomeric aldol product can be accessed by choosing the appropriate procedure. With earlier methods, stoichiometric quantities of chiral reagents were required for efficient asymmetric induction, with the auxiliary most often attached covalently to the substrate carbonyl. Lewis acid catalyzed addition reactions of silyl enolates to aldehydes (Mukaiyama reaction) later opened the way for catalytic asymmetric induction. In the last few years, both chiral metal complexes and small chiral organic molecules have been found to catalyse the direct aldol addition of unmodified ketones to aldehydes with relatively high chemical and stereochemical efficiency. These techniques along with the more recent developments in the area are discussed in this tutorial review.

Journal ArticleDOI
TL;DR: This tutorial review aims to encourage the use of the Pauson-Khand reaction by explaining the best ways of performing a PKR both in the stoichiometric and the catalytic version, showing the scope of the process and its limitations.
Abstract: There are still some synthetic chemists who hesitate to use metal-mediated or -catalysed reactions. The Pauson–Khand reaction (PKR) is a powerful transformation that has now been sufficiently well developed to be routinely considered when planning a synthesis, especially of polycyclic complex molecules. This tutorial review aims to encourage the use of this process explaining the best ways of performing a PKR both in the stoichiometric and the catalytic version, showing the scope of the process and its limitations. Additionally, asymmetry can be introduced in the reaction using several strategies, which will be discussed. The most recent examples of the synthetic applications of the PKR in natural product synthesis will give the reader an idea of the great usefulness of this reaction.

Journal ArticleDOI
TL;DR: This tutorial review deals with the most representative contributions in the field of supramolecular chirality, and centers on several examples that represent the control over chorality for self-assembled systems in solution.
Abstract: Self-assembly plays an important role in the formation of many (chiral) biological structures, such as DNA, α-helices or β-sheets of proteins. This process, which is the main tool of Supramolecular Chemistry (i.e. the chemistry of the molecular assemblies and of the intermolecular bonds), starts to play a significant role in nanotechnology for the construction of functional synthetic structures of nanometer size. The control of chirality in synthetic self-assembled systems is very important for applications of these systems e.g. in molecular recognition or mimicking of the catalytic activity of enzymes. This tutorial review deals with the most representative contributions in the field of supramolecular chirality. Specifically, the discussion centers on several examples that represent the control over chirality for self-assembled systems in solution.

Journal ArticleDOI
TL;DR: The sources and structures of dyes used to colour Western historical textiles are described in this tutorial review and direct analysis of dye isolated from artefacts allows comparison with the historical record.
Abstract: The sources and structures of dyes used to colour Western historical textiles are described in this tutorial review. Most blue and purple colours were derived from indigo—obtained either from woad or from the indigo plant—though some other sources (e.g. shellfish and lichens) were used. Reds were often anthraquinone derivatives obtained from plants or insects. Yellows were almost always flavonoid derivatives obtained from a variety of plant species. Most other colours were produced by over-dyeing—e.g. greens were obtained by over-dyeing a blue with a yellow dye. Direct analysis of dyes isolated from artefacts allows comparison with the historical record.

Journal ArticleDOI
Shuang Liu1
TL;DR: This critical review will focus on the role of coordination chemistry in the development of target-specific radiopharmaceuticals and the recent development in technetium, copper, gallium, indium, yttrium and lanthanide chemistry.
Abstract: There is a great current interest in developing target-specific radiopharmaceuticals for early detection of diseases and radiotherapy of cancers. This critical review will focus on the role of coordination chemistry in the development of target-specific radiopharmaceuticals. It will also discuss the recent development in technetium, copper, gallium, indium, yttrium and lanthanide chemistry, as well as analytical tools for quality control and characterization of radiolabeled small biomolecules (159 references).

Journal ArticleDOI
David Parker1
TL;DR: In this paper, the extent to which an enhanced understanding of the relationship between complex structure and spectral properties is emerging is discussed, together with an examination of the mechanism of ligand exchange processes.
Abstract: Lanthanide complexation chemistry has been studied intensively over the past 15 years and progress has been stimulated by the advent of well-defined, kinetically robust systems tailored to applications as bioactive probes for magnetic resonance and luminescence. In this tutorial review, the extent to which an enhanced understanding of the relationship between complex structure and spectral properties is emerging is discussed, together with an examination of the mechanism of ligand exchange processes. Such issues are aiding the development of responsive probes, ranging from simple sensors to more complex studies defining water structure and exchange dynamics.

Journal ArticleDOI
TL;DR: This tutorial review will briefly present the different systems studied and the reasons that led to the preparation of new systems with improved performances.
Abstract: In order to mimic the photosynthetic reaction centre and better understand photoinduced electron transfer processes, a family of compounds has been studied for the past 15 years. These are transition metal complexes, M(tpy)2 where tpy is a 2,2′:6′,2″ terpyridine based ligand, bearing on one side a donor group and on the other side an acceptor group. The resulting triad molecules or their two-component reference compounds (donor-M(tpy)2 and M(tpy)2-acceptor) can contain Ru, Os, Rh or Ir as the metal centre and both visible-light non absorbing groups and porphyrins as donor and acceptor groups. This tutorial review will briefly present the different systems studied and the reasons that led to the preparation of new systems with improved performances.

Journal ArticleDOI
TL;DR: Generation of cis-beta metallosalen and its related complexes, their structural features, and their application to asymmetric syntheses are summarized.
Abstract: Complexes of chiral salen and its related tetradentate Schiff-base ligands adopt three different configurations, trans, cis-α and cis-β. Of these complexes, trans-complexes have been widely used as catalysts for various asymmetric reactions. However, recent studies have disclosed that cis-β metallosalen and its related complexes show unique asymmetric catalyses that cannot be achieved by trans-metallosalen complexes. The present article summarizes generation of cis-β metallosalen and its related complexes, their structural features, and their application to asymmetric syntheses.

Journal ArticleDOI
TL;DR: This review summarizes recent progress in the development ofSupramolecular optical chemosensors for organic analytes based on artificial receptors for abiotic molecular devices that bind analytes by noncovalent interactions, producing a change in light absorption or fluorescence.
Abstract: Supramolecular optical chemosensors are abiotic molecular devices that bind analytes by noncovalent interactions, producing a change in light absorption or fluorescence. This review summarizes recent progress in the development of such chemosensors for organic analytes based on artificial receptors. Important design considerations, such as analyte affinity, choice of chromophore or fluorophore, binding selectivity, and optical signaling mechanism are briefly discussed. Chemists have fashioned chemosensors from a wide range of molecular structures, including polyalcohols, crown ethers, calixarenes, helicenes, sterically geared tripods, metal complexes, pinwheels, porphyrins, and fused-ring heterocycles. Analytes of interest include amines, carboxylic acids, amino acids, hydroquinones, alkaloids, carbohydrates, peptides, urea and creatinine.

Journal ArticleDOI
TL;DR: Minimum energy structures and vibrational frequencies predicted by Density Functional Theory agree with the experimental results, strongly supporting the identification of novel binary transition metal hydride species, which the matrix-isolation method is well-suited to investigate.
Abstract: Metal hydrides are of considerable importance in chemical synthesis as intermediates in catalytic hydrogenation reactions. Transition metal atoms react with dihydrogen to produce metal dihydrides or dihydrogen complexes and these may be trapped in solid matrix samples for infrared spectroscopic study. The MH2 or M(H2) molecules so formed react further to form higher MH4, (H2)MH2, or M(H2)2, and MH6, (H2)2MH2, or M(H2)3 hydrides or complexes depending on the metal. In this critical review these transition metal and dihydrogen reaction products are surveyed for Groups 3 though 12 and the contrasting behaviour in Groups 6 and 10 is discussed. Minimum energy structures and vibrational frequencies predicted by Density Functional Theory agree with the experimental results, strongly supporting the identification of novel binary transition metal hydride species, which the matrix-isolation method is well-suited to investigate. 104 references are cited.

Journal ArticleDOI
TL;DR: This critical review discusses in this critical review the mechanism of metal complexation, stability of metal cyclams and their structures, with particular emphasis on the variety of configurational states which metal cyclam can adopt.
Abstract: Cyclams are 14-membered tetraamine macrocycles which bind strongly to a wide range of metal ions. Medical interest has centred on clinical trials of a bicyclam for the treatment of AIDS and for stem cell mobilization, and on adducts with Tc and Cu radionuclides for diagnosis and therapy. Other potential applications particularly for Cr, Mn, Zn, and Ru cyclams are also emerging. We discuss in this critical review the mechanism of metal complexation, stability of metal cyclams and their structures, with particular emphasis on the variety of configurational states which metal cyclams can adopt. Understanding the factors which control the thermodynamics and kinetics of the interconversion of configurational states of metallo-cyclams may be a key factor in designing novel cyclam derivatives for future use in medicine. (136 References.)

Journal ArticleDOI
Gerhard Maas1
TL;DR: In this tutorial review, several different ruthenium complexes are presented which have recently emerged as suitable catalysts for carbenoid cyclopropanation.
Abstract: The transition-metal catalysed cyclopropanation of olefinic bonds using diazo compounds as a carbene source is among the best developed and most useful transformations available to the synthetic organic chemist. Nevertheless, the quest for new catalyst/ligand systems continues in order to further extend the scope of this method and to identify more economical catalytic systems. In this tutorial review, several different ruthenium complexes are presented which have recently emerged as suitable catalysts for carbenoid cyclopropanation. For the model reaction – cyclopropanation of styrene(s) with diazoacetates – and also for some intramolecular cyclopropanation reactions highly remarkable results in terms of catalyst efficiency, product yields, dia- and enantioselectivity have been reported.

Journal ArticleDOI
TL;DR: In this tutorial review applications of alkoxyamines as C-radical precursors for the conduction of tin-free radical reactions are presented and the use of microwave irradiation to conduct thermal radical reactions is discussed.
Abstract: In this tutorial review applications of alkoxyamines as C-radical precursors for the conduction of tin-free radical reactions are presented. These processes are controlled by the Persistent Radical Effect. A brief introduction on the Persistent Radical Effect is provided. In addition, the use of microwave irradiation to conduct thermal radical reactions is discussed. Finally, the use of alkoxyamines as initiators/mediators for the controlled/living radical polymerization is highlighted.

Journal ArticleDOI
TL;DR: This tutorial review summarises a collection of important contributions in the area, providing a flavour of the many types of phosphorus species that are participants in palladium catalyzed phosphorus-carbon bond formation.
Abstract: Underappreciated in the realm of palladium catalyzed cross-coupling chemistry is the formation of phosphorous-carbon bonds. This tutorial review summarises a collection of important contributions in the area, providing a flavour of the many types of phosphorus species that are participants in palladium catalyzed phosphorus-carbon bond formation. Recent developments include the usage of the cross-coupling reaction for preparation of phosphine ligands and the involvement of low molecular weight phosphinic acid derivatives for the synthesis of unsaturated phosphinic and phosphonic acid derivatives. Mechanistic cycles are offered in some instances. Stereochemical issues are addressed where applicable. The literature is covered to mid 2003.


Journal ArticleDOI
TL;DR: In this tutorial review, the two major pathways followed in the reaction of alkenes with alkynes catalysed by electrophilic transition metals are summarized.
Abstract: In this tutorial review we summarize the two major pathways followed in the reaction of alkenes with alkynes catalysed by electrophilic transition metals. If the metal coordinates simultaneously to the alkyne and the alkene, an oxidative cyclometallation can ensue to give a metallacyclopentene, which usually evolves by β-hydrogen elimination to give Alder-ene cycloisomerisation derivatives. On the other hand, coordination of the metal to the alkyne promotes the attack of the alkene to give metal cyclopropyl carbenes.