Publisher Summary This chapter discusses the analysis of total phenols and other oxidation substrates and antioxidants by means of Folin-Ciocalteu reagent. Analyses of the Folin-Ciocalteu (FC) type are convenient, simple, and require only common equipment and have produced a large body of comparable data. Under proper conditions, the assay is inclusive of monophenols and gives predictable reactions with the types of phenols found in nature. Because different phenols react to different degrees, expression of the results as a single number—such as milligrams per liter gallic acid equivalence—is necessarily arbitrary. Because the reaction is independent, quantitative, and predictable, analysis of a mixture of phenols can be recalculated in terms of any other standard. The assay measures all compounds readily oxidizable under the reaction conditions and its very inclusiveness allows certain substances to also react that are either not phenols or seldom thought of as phenols (e.g., proteins). Judicious use of the assay—with consideration of potential interferences in particular samples and prior study if necessary—can lead to very informative results. Aggregate analysis of this type is an important supplement to and often more informative than reems of data difficult to summarize from various techniques, such as high-performance liquid chromatography (HPLC) that separate a large number of individual compounds .The predictable reaction of components in a mixture makes it possible to determine a single reactant by other means and to calculate its contribution to the total FC phenol content. Relative insensitivity of the FC analysis to many adsorbents and precipitants makes differential assay—before and after several different treatments—informative.

Analysis of total phenols and other oxidation substrates and antioxidants by means of folin-ciocalteu reagent

Lanthanide-based luminescent hybrid materials.

http://www1.udel.edu/chem/polenova/PDF/Polyoxometalates/POMs_Catalysis_NMR_ChemRev1998.pdf

Catalysis by Heteropoly Acids and Multicomponent Polyoxometalates in Liquid-Phase Reactions

Publisher Summary This review is concerned with the neglected class of inorganic compounds, which contain ions of the same element in two different formal states of oxidation. Although the number of references cited in our review show that many individual examples of this class have been studied, yet they have very rarely been treated as a class, and there has never before, to our knowledge, been a systematic attempt to classify their properties in terms of their electronic and molecular structures. In the past, systems containing an element in two different states of oxidation have gone by various names, the terms “mixed valence,” nonintegral valence,” “mixed oxidation,” “oscillating valency,” and “controlled valency” being used interchangeably. Actually, none of these is completely accurate or all-embracing, but in our hope to avoid the introduction of yet another definition, we have somewhat arbitrarily adopted the phrase “mixed valence” for the description of these systems. The concept of resonance among various valence bond structures is one of the cornerstones of modern organic chemistry.

Mixed Valence Chemistry-A Survey and Classification

Great attention is currently paid to the synthesis of polynuclear transition metal complexes and the study of their photochemical, photophysical, and electrochemical properties. This interest is stimulated, in particular, by attempts to design and construct multicomponent systems (often called supramolecular species) capable of performing useful lightand/or redox-induced functions.1-16 A great deal of investigations on mononuclear transition metal complexes had previously shown that several families of these compounds are very interesting from the electrochemical, photochemical, and photophysical viewpoints.17-22 The metalligand interaction, in fact, is often (i) weak enough to allow the manifestation of intrinsic properties of metal and ligands (e.g., ligand-centered and metalcentered absorption bands and redox waves) and, at the same time, (ii) strong enough to cause the appearance of new properties, characteristic of the whole compound (e.g., metal-to-ligand or ligand-tometal charge-transfer bands). On passing from mononuclear to polynuclear transition metal complexes, the situation becomes even more interesting because in the latter (supramolecular) compounds one can find, besides properties related to each metal-based component, properties related to the structure and composition of the whole array. A suitable choice of the mononuclear building blocks and bridging ligands and an appropriate design of the (supramolecular) structure can in fact allow the occurrence of very interesting and potentially useful processes such as energy transfer along predetermined pathways, photoinduced charge separation, multielectron exchange at a predetermined potential, etc. The knowledge on the luminescence and redox properties of polynuclear transition metal complexes is rapidly accumulating, but it is disperse in a great number of journals. We have made an attempt to collect the available results, and we present them together with some fundamental introductory concepts and a few comments. One of the main problems, of course, was to delimit the field of this review. Using personal criteria which are related to our own research interests, we decided to consider only polynuclear transition metal complexes that can be defined as supramolecular species (section 2.2) and that are reported to exhibit luminescence. For such compounds only, the electrochemical properties have also been reviewed. Furthermore, we decided to include only classical (Werner-type) polynuclear transition metal compounds where the number of metal-based units is exactly known and the connection between the metal centers is provided only by bridging ligands. Thus, a number of interesting systems such as polymer-appended metal † In memoriam of Mauro Ciano. 759 Chem. Rev. 1996, 96, 759−833

Luminescent and Redox-Active Polynuclear Transition Metal Complexes.

Inorganic metal–oxygen cluster anions form a class of compounds that is unique in its topological and electronic versatility and is important in several disciplines. Names such as Berzelius, Werner, and Pauling appear in the early literature of the field. These clusters (so-called isopoly- and heteropolyanions) contain highly symmetrical core assemblies of MOx units (M = V, Mo, W) and often adopt quasi-spherical structures based on Archimedean and Platonic solids of considerable topological interest. Understanding the driving force for the formation of high-nuclearity clusters is still a formidable challenge. Polyoxoanions are important models for elucidating the biological and catalytic action of metal–chalcogenide clusters, since metal–metal interactions in the oxo clusters range from very weak (virtually none) to strong (metal–metal bonding) and can be controlled by choice of metal (3d, 4d, 5d), electron population (degree of reduction), and extent of protonation. Mixed-valence vanadates, in particular, show novel capacities for unpaired electrons, and the magnetic properties of these complexes may be tuned in a stepwise manner. Many vanadates also act as cryptands and clathrate hosts not only for neutral molecules and cations but also for anions, whereby a remarkable “induced self-assembly process” often occurs. Polyoxometalates have found applications in analytical and clinical chemistry, catalysis (including photocatalysis), biochemistry (electron transport inhibition), medicine (antitumoral, antiviral, and even anti-HIV activity), and solid-state devices. These fields are the focus of much current research. Metal–oxygen clusters are also present in the geosphere and possibly in the biosphere. The mixed–valence vanadates contribute to an understanding of the extremely versatile geochemistry of the metal. The significant differences between the chemistry of the polyoxoanions and that of the thioanions of the same elements is of relevance to heterogeneous catalysis, bioinorganic chemistry, and veterinary medicine.

Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines

Combined oxygen, in the form of water, metal oxides, silicates and other oxyions, accounts for about 50% by weight of the earth's crust. The chemistry of this most abundant element has two major aspects: that of water and aqueous solutions of electrolytes, and that of the solid state. The methodology and techniques appropriate for the study of these fields are sufficiently different that there have been very few points of contact between solution- and solid state chemists. One such contact, of great potential value, is provided by the extensive class of polyoxoanions formed by the transition metals of groups 5 and 6. As 'heteropoly and isopoly acids' these polyanions have been known and investigated for more than a century. The pre sent book is an attempt to survey the chemistry, structures, and applications of these species. Although the book forms part of a series in inorganic chemistry, the field of polyoxometalates deserves wider attention, for example, from organic chemists, especially those concerned with homogeneous and heterogeneous catalysis, and from biochemists, solid state- and materials scientists."

Heteropoly and Isopoly Oxometalates

Polyoxometalates: Very large clusters - Nanoscale magnets

Polyoxometalates: A Class of Compounds with Remarkable Topology.- A: Formation and Structure.- Equilibria of Polyoxometalates in Aqueous Solution.- Synthesis and Structural Chemistry of Novel Heteropolymolybdates and -tungstates.- Progress in Polytungstophosphate and -arsenate(V) Chemistry.- Crystal Structure Studies of Isopoly and Heteropoly Oxometalates. Structure of the Paradodecatungstate Molecule and Its Environment in Crystals.- Polyoxoanion-Supported Organometallic Complexes.- New Aspects of Non-Aqueous Polyoxometalate Chemistry.- Functionalization of Polyoxomolybdates: the Example of Nitrosyl Derivatives.- Polyoxoalkoxy Molybdenum and Vanadium Clusters.- Polyoxovanadates with Organic Ligands.- B: Spectroscopy and Magnetochemistry.- New Aspects of NMR Spectroscopy of Polyoxometalates.- Polyoxotungstates with Lone-Pair Assembling Atoms: Part 2: 183W NMR Structural Study of the Inorganic Cryptates [MAs4W40O140](28-n)- and [MSb9W21O86](19-n)-(Mn+ = Alkaline or Alkaline Earth Cation).- Blue Electron Distributions in Diamagnetic Reduced Heteropoly Tungstates. Insights Concerning Conduction Pathways and Spin Coupling Patterns. 183W NMR Chemical Shift Calculations.- Interactions between Delocalized and Localized Electrons in Heteropoly Blues Containing Paramagnetic Transition Metals. Magnetic Susceptibility and NMR Studies.- Polyoxovanadates: The Missing Link between Simple Paramagnets and Bulk Magnets?.- Molecular Magnetic Materials from Polyoxometalates.- The Use of Polyoxometalates in Charge Transfer Salts.- C: Applications-Catalysis and Biology.- Catalytic Chemistry of Solid Polyoxometalates and Their Industrial Applications.- Polyoxoanions in Homogeneous Catalysis: Polyoxoanion-Supported, Atomically-Dispersed Iridium, [(l,5-COD)Ir-P2W15Nb3O62]8-.- Palladium and Phosphomolybdovanadate Catalyzed Olefin Oxidation to Carbonyls.- Mixed Addenda Phosphomolybdovanadates as Catalysts for Oxidations Dioxygen and Hydrogen Peroxide.- Role of Vanadium in Oxidation Catalysis by Heteropolyanions.- Photocatalytic Processes by Polyoxometalates. Splitting of Water. The Role of Dioxygen.- Polyoxometalates for Molecular Devices: Antitumor Activity and Luminescence.- Polyoxometalates in Catalytic Selective Homogeneous Oxygenation and Anti-HIV Chemotherapy.- Of Therapy, Toxicity and Tungstates: The Anti-Retroviral Pharmacology of Polyoxometalates.- Polyoxometalates in AIDS Therapy.- Interactions of Oxovanadates and Selected Oxomolybdates with Proteins.

Polyoxometalates : from platonic solids to anti-retroviral activity

Introduction to Polyoxometalate Chemistry: From Topology via Self-Assembly to Applications M.T. Pope, A. Muller. Synthetic Strategies. 1. Rational Approaches to Polyoxometalate Synthesis R.J. Errington. 2. Functionalization of Polyoxometalates: Achievements and Perspectives A. Proust, R. Villaneau. 3. From the First Sulfurated Keggin Anion to a New Class of Compounds Based on the [M2O2S2 2+ Building Block M-Mo,W E. Cadot, et al. 4. Organometallic Oxometal Clusters A. Proust, et al. Structures: Molecular and Electronic. 5. Spherical (Icosahedral) Objects in Nature and Deliberately Constructable Molecular Keplerates: Structural and Topological Aspects O. Delgado, et al. 6. Synthesis and Crystal Structure Studies of Novel Selenium- and Tellurium-Substituted Lacunary Polyoxometalates B. Krebs, et al. 7. Vibrational Spectroscopy of Heteropoly Acids H. Ratajczak, et al. 8. Bond-Stretch Isomerism in Polyoxometalates? M.-M. Rohmer, et al. 9. Quantum-Chemical Studies of Electron Transfer in Transition-Metal Substituted Polyoxometalates S.A. Borshch, H. Duclusaud. Solution Equilibria and Dynamics. 10. Aqueous Peroxoisopolyoxometalates O.W. Howarth, et al. 11. Molybdate Speciation in Systems Related to the Bleaching of Kraft Pulp F. Taube, et al. 12. NMR Studies of Various Ligands Coordinated to Paramagnetic Polyoxometalates B.A. Kim, H. So. From Discrete Clusters to Networks and Materials. 13. Molecular Aspect of EnergyTransfer from Tb3+ to Eu3+ in the Polyoxometalate Lattices: An Approach for Molecular Design of Rare-Earth Metal-Oxide Phosphors T. Yamase. 14. Conducting and Magnetic Organic / Inorganic Molecular Materials Based on Polyoxometalates L. Ouahab, et al. 15. Molecular Materials From Polyoxometalates J.J. Borras-Almenar, et al. 16. Framework Materials Composed of Transition Metal Oxide Clusters M.I. Khan. 17. Perspectives in the Solid State Coordination Chemistry of the Molybdenum Oxides P.J. Hagrman, et al. 18. Polyoxometalate Clusters in a Supramolecular Self-Organized Environment: Steps Towards Functional Nanodevices and Thin Film Applications D.G. Kurth, D. Volkmer. 19. Polyoxometalate Chemistry: A Source for Unusual Spin Topologies D. Gatteschi, et al. 20. Heteropolyanions: Molecular Building Blocks for Ultrathin Oxide Films J.D. Powell, et al. Applications: Catalysis, Biological Systems, Environmental Studies. 21. Selective Oxidation of Hydrocarbons with Hydrogen Peroxide Catalyzed by Iron-substituted Silicotungstates N. Mizuno. 22. Aerobic Oxidations Catalyzed by Polyoxometalates A.M. Khenkin, et al. 23. Polyoxoanions in Catalysis: From Record Catalytic Lifetime Nanocluster Catalysis to Record Catalytic Lifetime Catechol Dioxygenase Catalysis R.G. Finke. 24. Ribosomal Crystallography and Heteropolytungstates D. Janell, et al. 25. Photocatalytic Decontamination by Polyoxometalates A. Hiskia, et al. Index.

Michael T. Pope

Papers

Polyoxometalate Chemistry: An Old Field with New Dimensions in Several Disciplines

Heteropoly and Isopoly Oxometalates

Polyoxometalates: Very large clusters - Nanoscale magnets

Polyoxometalates : from platonic solids to anti-retroviral activity

Polyoxometalate chemistry : from topology via self-assembly to applications