Showing papers in "Dalton Transactions in 2008"
TL;DR: A new set of covalent atomic radii has been deduced from crystallographic data for most of the elements with atomic numbers up to 96 and shows a well behaved periodic dependence that allows us to interpolate a few radii for elements for which structural data is lacking.
Abstract: A new set of covalent atomic radii has been deduced from crystallographic data for most of the elements with atomic numbers up to 96. The proposed radii show a well behaved periodic dependence that allows us to interpolate a few radii for elements for which structural data is lacking, notably the noble gases. The proposed set of radii therefore fills most of the gaps and solves some inconsistencies in currently used covalent radii. The transition metal and lanthanide contractions as well as the differences in covalent atomic radii between low spin and high spin configurations in transition metals are illustrated by the proposed radii set.
2,948 citations
TL;DR: The recent achievement of oxaliplatin for the treatment of colon cancer should not belie the imbalance between a plethora of investigated complexes and a very small number of clinically approved platinum drugs as discussed by the authors.
Abstract: Triggered by the resounding success of cisplatin, the past decades have seen tremendous efforts to produce clinically beneficial analogues. The recent achievement of oxaliplatin for the treatment of colon cancer should, however, not belie the imbalance between a plethora of investigated complexes and a very small number of clinically approved platinum drugs. Strategies opening up new avenues are increasingly being sought using complexes of metals other than platinum such as ruthenium or gallium. Based on the chemical differences between these metals, the spectrum of molecular mechanisms of action and potential indications can be broadened substantially. Other approaches focus on complexes with tumour-targeting properties, thereby maximizing the impact on cancer cells and minimizing the problem of adverse side effects, and complexes with biologically active ligands.
729 citations
TL;DR: The ligand types and structures of their complexes on one side and a set of the physico-chemical parameters governing properties of the CAs on the other side are discussed and the solid-state structures of lanthanide(III) complexes of open-chain and macrocyclic ligands and their structural features are compared.
Abstract: Magnetic resonance imaging is a commonly used diagnostic method in medicinal practice as well as in biological and preclinical research. Contrast agents (CAs), which are often applied are mostly based on Gd(III) complexes. In this paper, the ligand types and structures of their complexes on one side and a set of the physico-chemical parameters governing properties of the CAs on the other side are discussed. The solid-state structures of lanthanide(III) complexes of open-chain and macrocyclic ligands and their structural features are compared. Examples of tuning of ligand structures to alter the relaxometric properties of gadolinium(III) complexes as a number of coordinated water molecules, their residence time (exchange rate) or reorientation time of the complexes are given. Influence of the structural changes of the ligands on thermodynamic stability and kinetic inertness/lability of their lanthanide(III) complexes is discussed.
469 citations
TL;DR: Recent developments in the application of different ionic liquids as solvents or components of liquid and quasi-solid electrolytes for dye-sensitized solar cells are reviewed.
Abstract: The potential of room-temperature molten salts (ionic liquids) as solvents for electrolytes for dye-sensitized solar cells has been investigated during the last decade. The non-volatility, good solvent properties and high electrochemical stability of ionic liquids make them attractive solvents in contrast to volatile organic solvents. Despite this, the relatively high viscosity of ionic liquids leads to mass-transport limitations. Here we review recent developments in the application of different ionic liquids as solvents or components of liquid and quasi-solid electrolytes for dye-sensitized solar cells.
390 citations
TL;DR: The synthesis and performance of RE oxide, sulfoxide, vanadate, phosphate, fluoride, and sodium RE fluoride nanomaterials are summarized and the prospects of these promising materials as applied in the biological field is described to draw readers' attention and to attract more research interest.
Abstract: Inorganic fluorescent nanoparticles (NPs) have initiated an extensive upsurge in biological application research. Just as quantum dots are regarded as a vigorous reinforcement of the organic dye family, rare earth (RE) fluorescent NPs, as another phosphors branch, also possess unique optical characteristics. The advantages of RE NPs in photostability and colorimetric purity make them suitable for bioprobe applications. Since the preparation technologies have been well developed, it is favourable to prompt the research in the interdisciplinary field of biology and material sciences. Herein, we summarize the synthesis and performance, together with bioprobe applications of RE oxide, sulfoxide, vanadate, phosphate, fluoride, and sodium RE fluoride nanomaterials. The prospects of these promising materials as applied in the biological field is described to draw readers′ attention and to attract more research interest.
374 citations
TL;DR: The carbonate ion and the tetracyanoquinodimethane dianion are used as bridging ligands to generate targeted coordination polymers in what is intended that Dalton Perspectives be easily comprehensible to non-specialists in the field.
Abstract: This article, presented from a personal point of view, is concerned with the design of ligands intended to give specifically either binuclear or tetranuclear metal complexes or coordination polymers. No attempt is made to provide a comprehensive coverage of these topics, the focus being mainly upon results from our laboratory. Some emphasis is placed upon aspects of the historical development of the deliberate construction of coordination polymers (aka MOFs)—materials promising useful applications, the study of which continues to expand exponentially. Some of our recent research is described in which the carbonate ion and the tetracyanoquinodimethane dianion are used as bridging ligands to generate targeted coordination polymers. It is intended that Dalton Perspectives be easily comprehensible to non-specialists in the field; an average second year university chemistry student should be easily able to understand the present contribution.
355 citations
TL;DR: These studies show that the topology of the TNC provides a unique geometric and electronic structure particularly suited to carry out this key reaction in nature.
Abstract: In nature the four electron reduction of O2 to H2O is carried out by Cytochrome c oxidase (CcO) and the multicopper oxidases (MCOs). In the former, Cytochrome c provides electrons for pumping protons to produce a gradient for ATP synthesis, while in the MCOs the function is the oxidation of substrates, either organic or metal ions. In the MCOs the reduction of O2 is carried out at a trinuclear Cu cluster (TNC). Oxygen intermediates have been trapped which exhibit unique spectroscopic features that reflect novel geometric and electronic structures. These intermediates have both intact and cleaved O–O bonds, allowing the reductive cleavage of the O–O bond to be studied in detail both experimentally and computationally. These studies show that the topology of the TNC provides a unique geometric and electronic structure particularly suited to carry out this key reaction in nature.
306 citations
TL;DR: The hydrothermal reaction of M(NO3)2.6H2O with benzene-1,3,5-tricarboxylic acid and 1,2-bis(1,2,4-triazol-4-yl)ethane produced the mixed-ligand coordination polymers (MOFs) that feature trinuclear secondary building units (SBU) within the three-dimensional frameworks.
Abstract: The hydrothermal reaction of M(NO3)2·6H2O (M = Ni and Zn) with benzene-1,3,5-tricarboxylic acid (H3btc) and 1,2-bis(1,2,4-triazol-4-yl)ethane (btre) produced the mixed-ligand coordination polymers (MOFs) 3∞{[Ni3(µ3-btc)2(µ4-btre)2(µ-H2O)2]·∼22H2O} (1) and 3∞{[Zn3(µ4-btc)2(µ4-btre)(H2O)2]·2H2O} (3). The compounds, characterized by single-crystal X-ray diffraction, X-ray powder diffraction and thermoanalysis feature trinuclear secondary building units (SBU) within the three-dimensional frameworks. The trinuclear nickel unit in 1 exhibits an intra-trimer together with some weak inter-trimer antiferromagnetic coupling with J = −13.88(8) cm−1 from the magnetic susceptibility measurement between 1.9–300 K. The zinc coordination polymer 3 shows a strong fluorescence at 423 nm upon excitation at 323 nm (not seen in the free btre ligand). Compound 3 is thermally robust until 200 °C (ambient pressure) where loss of the water molecules starts. Careful control of the dehydration procedure (freeze-drying) for 1 and (heating to 280 °C) for 3 allowed for a solid-state reaction with single-crystal-to-single-crystal structural transformations in obtaining the largely dehydrated products 3∞{[Ni3(µ2-btc)2(µ4-btre)2(µ-H2O)2(H2O)2]·4H2O} (2) and 3∞{[Zn3(µ6-btc)2(µ4-btre)2]·∼0.67H2O} (4), respectively. In the transformation from 1 to 2 the unit cell volume is reduced to about 60%. The transition from 3 to 4 involves breakage and formation of new Zn–O bonds.
253 citations
TL;DR: The aim and scope of this review is to show the general validity of the 'complex-as-ligand' approach for the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity.
Abstract: The aim and scope of this review is to show the general validity of the ‘complex-as-ligand’ approach for the rational design of metallosupramolecular assemblies of increasing structural and magnetic complexity. This is illustrated herein on the basis of our recent studies on oxamato complexes with transition metal ions looking for the limits of the research avenue opened by Kahn's pioneering research twenty years ago. The use as building blocks of mono-, di- and trinuclear metal complexes with a novel family of aromatic polyoxamato ligands allowed us to move further in the coordination chemistry-based approach to high-nuclearity coordination compounds and high-dimensionality coordination polymers. In order to do so, we have taken advantage of the new developments of metallosupramolecular chemistry and in particular, of the molecular-programmed self-assembly methods that exploit the coordination preferences of metal ions and specifically tailored ligands. The judicious choice of the oxamato metal building block (substitution pattern and steric requirements of the bridging ligand, as well as the electronic configuration and magnetic anisotropy of the metal ion) allowed us to control the overall structure and magnetic properties of the final multidimensional nD products (n = 0–3). These species exhibit interesting magnetic properties which are brand-new targets in the field of molecular magnetism, such as single-molecule or single-chain magnets, and the well-known class of molecule-based magnets. This unique family of molecule-based magnetic materials expands on the reported examples of nD species with cyanide and related oxalato and dithiooxalato analogues. Moreover, the development of new oxamato metal building blocks with potential photo or redox activity at the aromatic ligand counterpart will provide us with addressable, multifunctional molecular materials for future applications in molecular electronics and nanotechnology.
245 citations
TL;DR: Quantum yield values up to 16% under visible irradiation associated with high turnover frequencies and stability and stability are characterized, characterize the new photocatalytic systems for hydrogen production, based on diimine derivatives of ruthenium, cyclometallated iridium or tricarbonylrhenium as photosensitizers and cobaloxime H2-evolving catalytic centers.
Abstract: Quantum yield values up to 16% under visible irradiation associated with high turnover frequencies ( approximately 50 h(-1)) and stability (up to 273 turnovers), characterize the new photocatalytic systems for hydrogen production, based on diimine derivatives of ruthenium, cyclometallated iridium or tricarbonylrhenium as photosensitizers and cobaloxime H2-evolving catalytic centers, which are among the most efficient molecular systems reported so far and compete with some platinum-based systems.
220 citations
TL;DR: An overview of the latest advances in the hydrothermal carbonization (HTC) process of functional carbonaceous materials from biomass shows that the HTC process can provide promising methods for the rational design of a rich family of carbonaceous and hybrid functional carbon materials with important applications.
Abstract: Recently, much attention has been attracted to the use of biomass to produce functional carbonaceous materials from the viewpoint of economic, environmental and societal issues. Among different techniques, the hydrothermal carbonization (HTC) process, a traditional but recently revived method, presents superior characteristics that make it a promising route of wide potential application. This perspective gives an overview of the latest advances in the HTC process of functional carbonaceous materials from biomass. First, we discuss the preparation of carbonaceous materials synthesized by the use of either highly directed or catalyst/template-assisted methods, from crude plant materials and carbohydrates respectively. These carbonaceous materials not only have special morphologies, such as nanospheres, nanocables, nanofibers, submicrocables, submicrotubes and porous structures, but also contain rich functional groups which can greatly improve hydrophilicity and chemical reactivity. Further, a general look is cast on the applications of this kind of carbonaceous materials in environmental, catalytic and electrical areas. Recent advances have demonstrated that the HTC process from biomass can provide promising methods for the rational design of a rich family of carbonaceous and hybrid functional carbon materials with important applications.
TL;DR: The extent to which profound differences, arising as a result of subtle changes in molecular structure, can be rationalised in terms of the nature of the frontier orbitals are considered.
Abstract: Once the Cinderella amongst the Platinum Group Metals at the Photochemistry Ball, iridium has become of intense interest since the beginning of the decade. Complexes of iridium(III) can be prepared that are highly luminescent, with emission wavelengths tuneable over the whole of the visible region. Whilst most studies have focused on tris-bidentate complexes, a rich and varied chemistry is also possible using tridentate ligands. In this review, we discuss the synthesis and excited-state properties of such complexes, exploring in particular how the number of cyclometallating carbon atoms in the coordination sphere of the metal ion influences the luminescence. Moving from [IrN6]3+ to [IrN3X3] coordination via [IrN5X]2+ and cis/trans-[IrN4X2]+ complexes, where N is a heterocyclic nitrogen and X is an anionic ligand or cyclometallated carbon, a whole range of luminescence efficiencies are encountered, ranging from the barely detectable to room temperature quantum yields approaching unity. We consider the extent to which these profound differences, arising as a result of subtle changes in molecular structure, can be rationalised in terms of the nature of the frontier orbitals.
TL;DR: The intrinsic topology of tetradentate ligands may introduce a fascinating reactivity and interesting electronic properties to the metal complexes of ambiphilic ligands.
Abstract: Multifunctional ligands with podand topology provide intrinsically well-defined coordination geometries. Several subgroups of multidentate ligand systems comprising dual functionality have been developed so far. Recent advances made in this research area reflect its topicality. Work on metal complexes of ambiphilic ligands consisting of Lewis-acidic Group 13 element bridgehead atoms and additional donor functionalities is in the current focus of interest. The intrinsic topology of tetradentate ligands may introduce a fascinating reactivity and interesting electronic properties to the metal complexes. Janus-head type ligands are very promising candidates for the preparation of multimetallic complexes.
TL;DR: The role of molybdenum doping in enhancing the photocatalytic activity of BiVO4 was investigated and discussed based on the changes of the surface acidity of the photoc atalyst.
Abstract: Transition metal doping has always suffered from the disadvantage of reduction of photocatalytic activity because the dopant ions can form a discrete level in the forbidden band of the photocatalyst resulting in low mobility of electrons and holes in the dopant level and thus lowered activity. However, in this study the photocatalytic activity of an efficient visible-light sensitive photocatalyst, BiVO4, for water oxidation or organic compound degradation was found to be remarkably enhanced by molybdenum doping. The role of molybdenum doping in enhancing the photocatalytic activity of BiVO4 was investigated and discussed based on the changes of the surface acidity of the photocatalyst.
TL;DR: The combination of diol-type ligands with paramagnetic transition metal ions has led to the isolation of new homometallic and heterometallic clusters, high-spin molecules and single molecule magnets ranging in nuclearity from two to forty four and with spin ground states as large as S = 61/2.
Abstract: The combination of diol-type ligands with paramagnetic transition metal ions has led to the isolation of a host of new homometallic and heterometallic clusters, high-spin molecules and single molecule magnets ranging in nuclearity from two to forty four and with spin ground states as large as S = 61/2. The ligands, whose cluster coordination chemistry is discussed in this article, are 1,3-propanediol and its derivatives, diethanolamine and its derivatives, pyridine-2,6-dimethanol and the gem-diol form of di-2-pyridyl ketone. The structural diversity of the complexes stems from the ability of the ligands to adopt a variety of bridging coordination modes depending on the positions of the two hydroxyl groups in the molecule, the presence/absence of extra donor groups and on the reaction conditions. Examples of ‘true’ reactivity chemistry involving clusters of diol-type ligands are also given. The activation of pyridine-2,6-dimethanol and di-2-pyridyl ketone by 3d-metal centres towards further reactions seems to be an emergent area of synthetic chemistry.
TL;DR: The superior electrochemical behaviour of disordered nano-Li[Ni(0.5)Mn(1.5]O(4-delta) has been correlated with AC impedance data, which suggests a modified surface for the nanomaterial prepared using the resorcinol-formaldehyde route compared with micron sized materials prepared by conventional solid state synthesis.
Abstract: Disordered and ordered forms of nano-Li[Ni0.5Mn1.5]O4 spinel, have been prepared by a one-pot resorcinol–formaldehyde synthesis. Lithium intercalation into disordered nano-Li[Ni0.5Mn1.5]O4−δ reveals good rate capability and cycling stability. It delivers 95.5% of the capacity at a rate of 10C (1500 mA g−1) and 88% at 20C (3000 mA g−1) compared with the capacity at low rate (0.2C). A capacity retention on cycling of 99.97% per cycle at 1C rate has also been observed. The superior electrochemical behaviour of disordered nano-Li[Ni0.5Mn1.5]O4−δ has been correlated with AC impedance data, which suggests a modified surface for the nanomaterial prepared using the resorcinol–formaldehyde route compared with micron sized materials prepared by conventional solid state synthesis.
TL;DR: A diversity of supramolecular rectangles that stacked into columns in the solid state has been obtained, opening new perspectives in the coordination-driven supramolescular organization of pi-conjugated systems.
Abstract: π-Conjugated organophosphorus derivatives have recently emerged as valuable building blocks for the tailoring of functional molecular materials. We have focused for ten years on the synthesis of phospholes bearing aromatic 2,5-substituents (phenyl, thienyl, pyridyl, etc.) and used these compounds as materials in fields as diverse as OLED's, WOLED's, non linear optics. Their properties (such as optical and electrochemical behaviour, thermal stability) can be finely tuned by functionalization at the P atom. Phosphole-based polymers have also been prepared by electropolymerization and have been used as sensors. More recently, phospholes substituted by one or two pyridyl groups have proven to act as multidentate ligands with original coordination properties. A diversity of supramolecular rectangles that stacked into columns in the solid state has been obtained, opening new perspectives in the coordination-driven supramolecular organization of π-conjugated systems. Chiral π-conjugated phospholes having a helical moiety have also been synthesized and spatially organized by using coordination to metallic ions, giving rise to sophisticated chiral complexes.
TL;DR: The deliberate chemically-induced structural distortion of the [Mn6] molecule allows the isolation of analogous family members displaying remarkably different magnetic properties and this in turn allows for a rare semi-quantitative magneto-structural correlation which enables prediction of the magnetic properties of new family members.
Abstract: The use of derivatised salicylaldoximes in Mn chemistry has led to the isolation of a plethora of beautiful new SMMs ranging in nuclearity from three to eight and with spin ground states as large as S = 12–including a Mn6 complex with the largest energy barrier to magnetisation reversal yet reported. The deliberate chemically-induced structural distortion of the [Mn6] molecule allows the isolation of analogous family members displaying remarkably different magnetic properties and this in turn allows for a rare semi-quantitative magneto-structural correlation which enables prediction of the magnetic properties of new family members.
TL;DR: In the present Perspective, an overview of the results of the preparation and synthetic application of cyclic oxonium derivatives of polyhedral boron hydrides is presented.
Abstract: Cyclic oxonium derivatives of polyhedral boron hydrides are a relatively new class of boron compounds. They have great potential for the modification of various types of organic and bioorganic molecules and the synthesis of compounds that could be used in different fields from the treatment of nuclear wastes to the treatment of cancer. In the present Perspective we would like to present an overview of the results of the preparation and synthetic application of these compounds.
TL;DR: The structural differences described indicate the importance of carboxylate ligands and metals in the framework formation of coordination complexes and a rare 3-fold interpenetrated 3-connected 10(3)-ths net.
Abstract: A series of mixed-ligand coordination complexes, namely [Zn(CA)2(BIE)] (1), [Zn(OX)(BIE)]·H2O (2), [Zn2(m-BDC)2(BIE)2] (3), [Cd(m-BDC)(BIE)] (4), [Cd(5-OH-m-BDC)(BIE)] (5), [Zn(5-OH-m-BDC)(BIE)] (6), [Zn2(p-BDC)2(BIE)2]·2.5H2O (7), [Cd3(p-BDC)3(BIE)] (8), [Cd3(BTC)2(BIE)2]·0.5H2O (9) and [Zn(BTCA)0.5(BIE)] (10), where CA = cinnamate anion, OX = oxalate anion, m-BDC = 1,3-benzenedicarboxylate anion, 5-OH-m-BDC = 5-OH-1,3-benzenedicarboxylate anion, p-BDC = 1,4-benzenedicarboxylate anion, BTC = 1,3,5-benzenetricarboxylate anion, BTCA = 1,2,3,4-butanetetracarboxylate anion, and BIE = 2,2′-bis(1H-imidazolyl)ether, were synthesized under hydrothermal conditions. In 1, a pair of BIE ligands bridge adjacent Zn(II) atoms to give a centrosymmetric dimer. In 2 and 3, BIE ligands connect Zn(II)–carboxylate chains to form hexagonal honeycomb 63-hcb and square 44-sql layers, respectively. In 4 and 5, m-BDC and 5-OH-m-BDC bridge Cd(II) atoms to give dimeric units, respectively, which are further linked by BIE ligands to form sql nets. In 6, the BIE ligands extend the Zn(II)–carboxylate chains into 2D sinusoidal-like sql nets. The undulated sql nets polycatenate each other in the parallel manner with DOC (degree of catenation) = 2, yielding a rare 2D → 3D parallel polycatenation net. In 7, the BIE and p-BDC ligands link the Zn(II) atoms to give a rare 3-fold interpenetrated 3-connected 103-ths net. 8 contains unusual edge-sharing polyhedral rods formed by [Cd3(CO2)6] clusters. Each rod is connected by the benzene rings of p-BDC in four directions into a simple α-Po topology. In 9, two kinds of different 2D Cd–BTC layers are alternately linked to each other by sharing Cd(II) centers to form a 3D framework, which is further linked by two kinds of BIE ligand to produce a complicated 3D polymeric structure. 10 possesses a unique (3,4)-connected 3D framework with (83)2(85·10) topology. The structural differences described indicate the importance of carboxylate ligands and metals in the framework formation of coordination complexes. The infrared spectra, thermogravimetric and luminescent properties were also investigated in detail for the compounds.
TL;DR: This Perspective discusses the current progresses of these representative reversible or irreversible material systems, aiming at providing an outline of the forefront of hydrogen storage materials/technologies for transportation applications.
Abstract: Hydrogen-rich boron-containing compounds have received extensive attention as potential hydrogen storage media for vehicular applications. The past years have seen significant progresses in material discovery, material composition/structure tailoring, catalyst identification and regeneration chemistry, which give rise to state-of-the-art hydrogen storage materials/technologies. Lithium tetrahydroborate-related materials exhibit the hitherto highest reversible hydrogen capacity via solid–gas reactions. Catalytic hydrolysis of sodium tetrahydroborate offers an on-demand hydrogen generation system for vehicular applications. Ammonia borane-related materials exhibit a satisfactory combination of material properties that are suited for on-board hydrogen sources, coupled with significant advances in spent fuels regeneration. This Perspective discusses the current progresses of these representative reversible or irreversible material systems, aiming at providing an outline of the forefront of hydrogen storage materials/technologies for transportation applications.
TL;DR: The frontiers of novel photoresponsive materials constructed with photochromes and transition metal complexes are surveyed in this review, and strategies to develop new photofunctions are categorized into four types.
Abstract: The frontiers of novel photoresponsive materials constructed with photochromes and transition metal complexes are surveyed in this review. Strategies to develop new photofunctions are categorized into four types. In the first category, intramolecular electronic interactions between photochromes and metal complexes produce entangled responses such as redox-regulated photochromic reactions or tristable photochromism. In the second, light-induced molecular structural rearrangements of photochromes induce the transformation of flexible and labile coordination structures, which can be applied to complex photomechanics or photoelectron conversion. In the third, the photochromic moiety also acts as a photonic switch, transmitting a metal–metal interaction when it is located between two metal complex moieties. The last category concerns the development of new photochromic reactions, involving metal–ligand bond rearrangements. These reactions potentially induce drastic electronic tuning of the metal center, and can be used to develop light-driven molecular machines.
TL;DR: Application of ILs as the extracting phase provided unprecedented enhancement of the extraction performance of TODGA for lanthanides compared with that of the isooctane system, and it was clarified that TODGA provided selectivity for the middle Lanthanides in the ILs systems, but heavier lanthanide in the isosoftane system.
Abstract: Liquid–liquid extraction of lanthanides from aqueous solutions into ionic liquids (ILs) has been investigated using N,N,N′,N′-tetra(n-octyl)diglycolamide (TODGA) as an extractant, and compared with that in the isooctane system. Application of ILs as the extracting phase provided unprecedented enhancement of the extraction performance of TODGA for lanthanides compared with that of the isooctane system. Slope analysis confirmed that TODGA in ILs formed a 1 : 3 complex with La3+, Eu3+, or Lu3+. On the other hand, the molar ratios of species extracted into isooctane were 1 : 3 for La3+ or 1 : 4 for Eu3+ and Lu3+, depending on the atomic number of the lanthanide. The transfer of lanthanides with TODGA into ILs proceeded via a cation-exchange mechanism, in contrast to ion pair extraction in the isooctane system. Furthermore, we clarified that TODGA provided selectivity for the middle lanthanides in the ILs systems, but heavier lanthanides in the isooctane system.
TL;DR: The theme of this article focuses on the approaches towards the rational design of platinum(II) and gold(III) complexes with antitumour properties based on the updated understanding of the mechanism of action of these compounds.
Abstract: Metal complexes afford an opportunity for the discovery of new antitumour drugs with truly novel mechanisms of action. Various tactics and some new concepts have been employed to improve the physico-chemical and biological properties of metal complexes. Recent advances in this area demonstrate a bright prospect for the utilization of metal complexes in cancer chemotherapy. The theme of this article focuses on the approaches towards the rational design of platinum(II) and gold(III) complexes with antitumour properties based on the updated understanding of the mechanism of action of these compounds. The complexes summarized in this work include monofunctional platinum(II) complexes, multinuclear platinum(II) complexes, hybrid and targeted platinum(II) complexes, and gold(III) complexes. Most of them violate the established structure-activity relationships and demonstrate different reactivities from cisplatin and thereby show some potential for the prevention of detoxification.
TL;DR: Recent progress on subporphyrin chemistry and unprecedented ring-splitting reactions of medium size expanded porphyrins that are triggered upon metallation are reviewed.
Abstract: Subporphyrin is a ring-contracted porphyrin congener consisting of three pyrrolic subunits domed in a C3 symmetric bowl arrangement. Subporphyrin had long been elusive until the first synthesis of tribenzosubporphine in 2006. Shortly after, synthetic protocols of subpyriporphyrin, meso-aryl-substituted subporphyrins, and meso-aryl substituted subchlorins were developed. Subporphyrins display interesting properties including distinct aromaticity arising from 14π-electronic conjugation, green fluorescence, and strong influences of meso-aryl substituents on the electronic network of the macrocycle. Besides the rational synthetic routes, an unexpected route to a specific subporphyrin from a [32]heptaphyrin(1.1.1.1.1.1.1) was discovered via a thermal extrusion reaction upon Cu(II)–B(III) cooperative metallation. In this Perspective, we review recent progress on subporphyrin chemistry and unprecedented ring-splitting reactions of medium size expanded porphyrins that are triggered upon metallation.
TL;DR: Only 5 alters the DNA superhelicity upon binding with supercoiled pBR322 DNA, which is consistent with its higher DNA binding affinity, and the cytotoxicities of the complexes against human cervical epidermoid carcinoma cell line (ME180) have been examined.
Abstract: A series of mixed ligand ruthenium(II) complexes [Ru(Hdpa)2(diimine)](ClO4)21–5, where Hdpa is 2,2′-dipyridylamine and diimine is 1,10-phenanthroline (phen) and a modified/extended 1,10-phenanthroline such as, 5,6-dimethyl-1,10-phenanthroline (5,6-dmp), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), 5-methyldipyrido[3,2-d:2′,3′-f]quinoxaline (mdpq) and dipyrido[3,2-a:2′,3′-c]phenazine (dppz) have been isolated and characterized by analytical and spectral methods The complex [Ru(Hdpa)2(phen)](PF6)21 has been structurally characterized and the coordination geometry around Ru(II) in it is described as distorted octahedral 1H NMR spectral data reveal that 1–5 should have a C2 symmetry lying on the diimine plane due to the rapid flapping of the coordinated Hdpa ligands The interaction of the complexes with calf thymus (CT) DNA has been explored by using absorption and emission spectral and viscometry and electrochemical techniques and the mode of DNA binding of the complexes has been proposed The DNA binding affinity of the complexes decreases with decrease in number of planar aromatic rings in the co-ligand supporting the intercalation of the diimine co-ligands in between the DNA base pairs Circular dichroic spectral studies reveal that the complexes 3–5 exhibit induced circular dichroism upon binding to CT DNA Interestingly, upon interaction with CT DNA all the complexes show an increase in anodic current in the cyclic voltammograms suggesting that they are involved in electrocatalytic guanine oxidation Interestingly, of all the complexes, only 5 alters the DNA superhelicity upon binding with supercoiled pBR322 DNA, which is consistent with its higher DNA binding affinity Further, the cytotoxicities of the complexes against human cervical epidermoid carcinoma cell line (ME180) have been examined Interestingly, 5 exhibits a cytotoxicity against ME180 higher than other complexes with potency approximately 8 times more than cisplatin for 24 h incubation but 4 times lower than cisplatin for 48 h incubation
TL;DR: An historical perspective of this biomimetic structural approach is given and recently reported bio-inspired functional mimics displaying electrocatalytic activity for hydrogen production are focused on.
Abstract: NiFe hydrogenases are unique enzymes that catalyze the H+/H2 interconversion with remarkable efficiency. The determination of the tridimensional structure of their active site (a sulfur-rich dinuclear nickel–iron cluster with diatomic cyanide and carbonyl ligands) has stimulated the synthesis of a variety of nickel-based complexes as potential electrocatalysts for hydrogen production. These catalysts may provide an adequate alternative to platinum. This paper gives an historical perspective of this biomimetic structural approach and then focusses on recently reported bio-inspired functional mimics displaying electrocatalytic activity for hydrogen production.
TL;DR: The structural differences indicate that the backbone of such dicarboxylate ligands plays an important role in governing the structures of such metal-organic coordination architectures, and the chelating bipyridyl-like ligand H leads to the formation of these coordination polymers with one-dimensional structures by occupying the coordination sites of metal ions.
Abstract: Seven new d10 metal coordination polymers with isomeric benzenedicarboxylates and 3-(2-pyridyl)pyrazole ligands, [Zn2L2(1,2-BDC)(H2O)]n (1), {[Cd2(HL)2(1,2-BDC)2]·H2O}n (2), [Cd(HL)(1,2-BDC)(H2O)]n (3), [Zn(HL)(1,3-BDC)(H2O)·3H2O]n (4), [Cd2L2(1,3-BDC)(H2O)]n (5), [Zn(HL)2(1,4-BDC)]n (6) and [Cd(HL)2(1,4-BDC)]n (7) (BDC = benzenedicarboxylate, HL = 3-(2-pyridyl)pyrazole), have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses reveal that each complex takes a different one-dimensional (1D) chain structure. In 1–7, the BDCs act as bridging ligands, exhibiting rich coordination modes to link metal ions. The three BDC isomers exhibit different coordination modes: µ1-η1:η1/µ3-η2:η1, µ3-η1:η2/µ3-η2:η1, µ2-η1:η1/µ1-η1:η0 and µ1-η1:η1/µ1-η1:η0 for 1,2-BDC, µ1-η1:η1/µ1-η1:η0 and µ1-η1:η0/µ2-η2:η1 for 1,3-BDC, and µ1-η1:η0/µ1-η0:η1, µ1-η1:η0/µ1-η1:η0 and µ1-η1:η1/µ1-η1:η1 for 1,4-BDC, respectively. In these complexes, HL acts as a simple bidentate chelate ligand (in 2, 3, 4, 6 and 7), similar to 2,2′-bipyridine, or as a tridentate chelate-bridging ligand (in 1 and 5) via deprotonation of the pyrazolyl NH group and coordination of the pyrazolyl N atom to a second metal ion. The structural differences indicate that the backbone of such dicarboxylate ligands plays an important role in governing the structures of such metal–organic coordination architectures, and the chelating bipyridyl-like ligand HL leads to the formation of these coordination polymers with one-dimensional structures by occupying the coordination sites of metal ions. Moreover, the photoluminescent properties of complexes 1–7 were also studied in the solid-state at room temperature.
TL;DR: Recent work on porous pillared zirconium diphosphonates, and the newer and in many respects different characteristics of tin(iv) phosphonates are described.
Abstract: The past decade has witnessed an exponential growth of metal organic framework compounds (MOFs). The defining character of these compounds is their porosity. However, in many cases no effort was made to show evidence that a stable porous structure has been achieved and that the pores may be accessed. In the present paper we describe recent work on porous pillared zirconium diphosphonates, and the newer and in many respects different characteristics of tin(IV) phosphonates. The Sn(IV) monophosphonates form spherical globules that exhibit very high surface areas. The surface area arises from their nano-sized particles that pack in a “house of cards” arrangement. Also, it is shown that the 1,4-monophenyldiphosphonic acid forms highly porous (250–400 m2 g−1) materials with Sn(IV) when prepared in alcohol–water media. This is not the case with analogous Zr(IV) compounds. The many variations in the syntheses of both the zirconium and tin aryl- and alkyldiphosphonate pillars and their combinations with spacers such as methyl- and monophenylphosphonic acid have created a variety of highly porous materials that are stable to 400 °C in air, highly stable in acid media, do not collapse when de-solvated, and can be post and presynthesis altered to include functional groups. Several new directions taken by other researchers are also described. However, it is emphasized in this presentation that the cross-linked compounds form particles that precipitate rapidly into nanoparticles that exhibit only short range order. Therefore, they differ from the more conventional MOFs in that they are not amenable to structure solution by X-ray or neutron diffraction techniques. Rather, they must be understood on the basis of modeling and indirect data from EM, NMR, and additional spectroscopic and textural studies.
TL;DR: The case is supported that the neurotoxic agent in Alzheimer's disease is a soluble aggregated form of the amyloid beta peptide (Abeta), probably complexed with divalent copper, and the structure and chemical properties of the monomeric peptide and its Cu(ii) complex are discussed.
Abstract: In this article, we support the case that the neurotoxic agent in Alzheimer's disease is a soluble aggregated form of the amyloid beta peptide (Abeta), probably complexed with divalent copper. The structure and chemical properties of the monomeric peptide and its Cu(ii) complex are discussed, as well as what little is known about the oligomeric species. Abeta oligomers are neurotoxic by a variety of mechanisms. They adhere to plasma and intracellular membranes and cause lesions by a combination of radical-initiated lipid peroxidation and formation of ion-permeable pores. In endothelial cells this damage leads to loss of integrity of the blood-brain barrier and loss of blood flow to the brain. At synapses, the oligomers close neuronal insulin receptors, mirroring the effects of Type II diabetes. In intracellular membranes, the most damaging effect is loss of calcium homeostasis. The oligomers also bind to a variety of substances, mostly with deleterious effects. Binding to cholesterol is accompanied by its oxidation to products that are themselves neurotoxic. Possibly most damaging is the binding to tau, and to several kinases, that results in the hyperphosphorylation of the tau and abrogation of its microtubule-supporting role in maintaining axon structure, leading to diseased synapses and ultimately the death of neurons. Several strategies are presented and discussed for the development of compounds that prevent the oligomerization of Abeta into the neurotoxic species.