bluuebunny/crossref_metadata_2025 huggingface dataset:
X‐Ray Powder Diffraction
Authors: Clearfield Abraham , Bhuvanesh Nattamai
Published: December 2011

Crystalline solids may be described as containing a unit of matter that when repeated in three‐dimensional space reproduces the crystal. Because of the periodic nature of crystals and the fact that the distances between the atoms, that is, bond distances, are of the same order of magnitude as X‐ray wavelengths, the crystals act as diffraction gratings toward X‐ray beams. Diffraction from a small single crystal produces a three‐dimensional array of spots whose geometry can be related to the geometry of the unit cell and the three noncoplanar vectors that describe the periodic arrangement of the unit cells. Knowledge of the intensities of the diffracted radiation allows the determination of the atoms within the unit cell.

Many compounds occur as polycrystalline solids or powders. Most solids in nature are present as mixtures of two or more crystalline phases. Such materials still diffract X‐rays but the three‐dimensional array of spots is condensed into a one‐dimensional array of diffraction lines or near Gaussian peaks. Because of this low dimensionality much less data are obtained; however, a great deal of information may still be derived from the powder pattern referred to as X‐ray powder diffraction (XRPD) for XRPD pattern. In its simplest form the XRPD may be used as a fingerprint to identify a particular phase or mixture of phases. The amount of each phase may be determined quantitatively.

As the crystallite size decreases, the X‐ray peaks broaden, so it is possible to obtain a measure of the crystallite size. Lattice strain also contributes to peak broadening, requiring that the two effects be separated for accuracy in interpretation of the data. The advent of high speed computers and highly engineered diffractometers allows for rapid accurate analysis of powder mixtures or the study of solid solutions, defects and other complexities of crystalline material. It is, in many cases, possible to determine the crystal structure of compounds from their X‐ray powder data and this aspect of powder diffractometry is included here. Diffraction does not occur from amorphous solids, but X‐rays are scattered and much information on particle size and short range order can be obtained from small angle X‐ray and neutron scattering studies. Furthermore, EXAFS and Atomic Pair Distribution functions provide a means of probing the structures of amorphous and semicrystalline materials.
Circular Dichroism (
CD
) Spectroscopy
Authors: Presta P. Anthony , Stillman Martin J.
Published: December 2011

Circular dichroism (CD) spectroscopy is of fundamental importance as a tool in all areas of chemistry and biochemistry because this technique is the simplest and fastest measure of the presence of the chiral species that lead to optical activity. Chiral centers and chiral species exist from the simplest molecules to complex organic molecules, from inorganic complexes to metal‐based biological molecules, typically metalloproteins; from folded polymers, which are typically peptides and proteins; to the supramolecular organization of the quaternary structure of proteins; including all forms of helical structure typified by the the double helix; to liquid crystals and beyond, to even more massive and organized species. For all these species, CD spectroscopy provides insight into the presence and the extent of the chiral electric field induced by the atomic and molecular organization. The optical activity is detected under electronic and vibrational absorption bands as a result of the differential absorption of left‐ and right‐circularly polarized light. Measurement of mirror images of the CD spectrum is commonly used to determine the enantiomeric purity of small molecules. The measurement of the change, and sometimes loss, of optical activity measured in the spectral region of the chiral chromophores can be used to determine and understand the denaturation of a folded protein as the chirality changes with the change in gross structural features associated with the folding.

We focus particularly in this chapter on the influence of metals on the chiral properties of proteins. Metal binding results in changes in molecular and supramolecular conformations readily measured under metal‐based spectral bands. In cases for which the folding of the protein is almost entirely metal‐induced, the CD spectrum becomes an extremely sensitive marker for structural change as a function of metal loading allowing both the stoichiometry of metal binding and the coordination geometry to be proposed.

Measurement of the chirality of a molecule is easy in the region 190–1000 nm as several relatively inexpensive instruments provide high sensitivity. Time‐resolved CD spectral data are also readily achievable using stopped‐flow devices. Measurement in the infrared regions is also popular and provides invaluable information; instruments can now be purchased “off the shelf”. The new growth area is the use of synchrotron radiation as the light source allowing CD spectral data to be measured in all regions of the electromagnetic spectrum, but particularly, for energies higher than 50 000 cm
−1
(below 200 nm).
Electrochemistry
Authors: Elvington Mark C. , Brewer Karen J.
Published: December 2011

This chapter provides a summary of electrochemical methods with an emphasis on applications to inorganic chemistry. Electrochemical methods include potential sweep, potential step, and bulk methods including coupling of bulk electrolysis methods to characterization methods. Discussions include examples from the literature and important experimental considerations. Techniques discussed include cyclic voltammetry, differential pulse voltammetry and polarography, square wave voltammetry, and bulk electrolysis. The coupling of analysis methods including electronic absorption, IR and EPR spectroscopy to bulk electrolysis are provided. Discussions are tailored to the application of electrochemistry in inorganic chemistry research with practical considerations and illustrative examples provided.
Electron Paramagnetic Resonance (
EPR
) Spectroscopy
Authors: Hales Brian J.
Published: December 2011

Electron‐Paramagnetic Resonance (EPR) spectroscopy, also know as Electron‐Spin Resonance (ESR) spectroscopy, monitors the energy levels of paramagnetic molecules. The major energy interaction (Zeeman Interaction) is between the magnetic moment of the electron and the field of a large uniform magnet. This interaction splits the normally degenerate spin levels of the electron and the electron‐paramagnetic resonance (EPR) spectrometer measures the energy of this interaction. The EPR spectrometer is described along with a discussion of spectral optimization techniques. Additionally, energy interaction terms are described and include hyperfine coupling (the interaction of the magnetic moments of the unpaired electron and magnetic nuclei) and spin‐orbit coupling, which influences the magnitude of the spectroscopic
g
‐factor and the energy levels of
S
 > 1/2 systems. The general features of half‐integer and integer high‐spin systems are further described, including examples.
Electron Spin Echo Envelope Modulation (ESEEM) Spectroscopy
Authors: McCracken John
Published: December 2011

In the 46 years since its discovery in Ce(III)‐doped CaWO4single crystals, electron spin echo envelope modulation (ESEEM) spectroscopy has developed into an important method for the characterization of paramagnetic centers. The capability of ESEEM to resolve ligand hyperfine couplings to paramagnetic transition metal ions in powder or frozen solution samples, and its sensitivity to the orientation and number of coupled nuclei, make it a valuable tool for structural biology and materials chemistry. This article presents a brief history of the method from its discovery to the development of commercial instrumentation that has provided an opportunity for scientists to address difficult questions regarding coordination chemistry in paramagnetic systems. The technical background section presents the three most basic ESEEM experiments: the one‐dimensional primary echo (two‐pulse) and stimulated echo (three‐pulse) experiments and the two‐dimensional, four‐pulse hyperfine sublevel correlation (HYSCORE) experiment. The mathematical expressions developed for these experiments and the simpleS = 1/2,I = 1/2 coupled spin system, will be used together with sample ESEEM data from Cu(II) centers in a model complex and an enzyme to illustrate the strengths and weaknesses of these pulse schemes. The article will conclude with a case study of the nonheme Fe(II) site in taurine/α‐ketoglutarate dioxygenase (TauD) that will feature some of the strengths of one‐dimensional and two‐dimensional ESEEM spectroscopy and show that the method has matured into a powerful technique for elucidating the coordination chemistry of this important class of enzymes as well as many other systems.
Biomedical Applications of Magnetic Nanoparticles
Authors: Prasad Nand Kishore , Bahadur Dhirendra , Vasseur Sébastien , Duguet Etienne
Published: December 2011

Magnetism, which is an intrinsic property of every atom, has a profound influence on living organisms. Magnetism of nanoparticles plays a strong role in certain specific applications of health care. More particularly, several magnetic inorganic oxides, such as iron oxides, which are biocompatible, have been extensively used for several medical applications in their nanometric form. These applications/perspectives include magnetic resonance imaging (MRI) contrast enhancement, hyperthermia treatment of cancer, targeted drug delivery, and biological entity separation or identification. This article examines these applications through an understanding of the problems involved and the current and future possibilities for resolving them.
Inorganic Semiconductor Nanomaterials for High‐Performance Flexible Electronics
Authors: Ahn Jong‐Hyun , Baca Alfred J. , Rogers John A.
Published: December 2011

This article reviews several classes of high‐quality inorganic semiconductor nanomaterials for high‐performance flexible and stretchable electronics in two‐ or three‐dimensional layouts. Approaches for fabricating inorganic semiconductors in the forms of wires, ribbons, and membranes, and methods for integrating these materials on flexible substrates are presented. Finally, perspectives on the trends for future work related to flexible electronics are described.
Liquid‐Phase Synthesis of Inorganic Nanoparticles
Authors: Caruntu Gabriel , Caruntu Daniela , O'Connor Charles J.
Published: December 2011

In this article we review some of the most representative liquid‐phase synthetic methodologies for the preparation of inorganic nanoparticles. Metallic nanoparticles and alloys have been chosen as a model to discuss the preparation of colloidal nanocrystals and their functionalization with organic molecules. Of a particular interest have been the synthetic methodologies allowing not only the compositional control of the nanoparticles but also the size/shape of the nanoparticles along with their ability to organize into hierarchical architectures suitable for different technological applications.
Multicolor Quantum Dots in Molecular Profiling of Cancer Cells and Tissues
Authors: Zrazhevskiy Pavel , Gao Xiaohu
Published: December 2011

Cancer represents a serious threat to our health despite considerable effort by scientific and medical community to combat this disease. It has been shown that detection of specific tumor biomarkers is important for cancer diagnosis and targeted therapy. However, a vast genetic and phenotypic variability of cancer first requires appropriate molecular characterization of cancer using conventional immunohistochemistry (IHC) techniques. Being single color and semiquantitative in nature, IHC methods are unable to address the need of quantitative multiplexed molecular profiling of clinical tissue samples. Therefore, development of new molecular profiling technologies is necessary for quantitative analysis of molecular signatures of individual patient's tumors. Quantum dots are emerging as a new class of fluorescent probes for biomolecular and cellular imaging. Owing to their unique optical properties, such as size‐tunable light emission, simultaneous excitation of multiple colors, improved brightness, resistance to photobleaching, and extremely large Stokes shift, quantum dots represent a highly promising tool for detection and quantification of multiple biomarkers in cells, tissue samples, and even live organisms. This functionality will allow researchers to correlate a panel of cancer biomarkers with cancer behavior and clinical outcome and will open new opportunities for the development of personalized treatment schemes targeted specifically against markers expressed. Multiplexed marker detection will also provide a high‐throughput tool for marker screening in cancer research.
Gold Nanoparticles: Monolayer‐Protected Scaffolds and Building Blocks
Authors: Ofir Yuval , Srivastava Sudhanshu , Rotello Vincent M.
Published: December 2011

Nanoparticles provide key tools for bridging the gap between “bottom‐up” synthetic methods and “top‐down” fabrication. In this article, we describe recent progress in the recognition‐mediated assembly of metal nanoparticles using small molecules and polymers. A significant portion of the article focuses on the interaction of nanoparticles with biological moieties such as peptides and proteins, and the use of nanoparticles as drug and gene carriers for application in biomedical applications.
Inorganic Nanobelt Materials
Authors: Yu Shu‐Hong , Yao Wei‐Tang
Published: December 2011

The aim of this article is to provide a comprehensive review of current research activities that center around inorganic nanobelts. We begin with an overview of synthetic strategies and principles that have been developed for generating 1‐D nanobelts with vapor‐phase growth as well as solution‐based growth routes. We then discuss the synthesis and structure of various inorganic nanobelts, which include elements, oxides, hydroxyl sulfates, chalcogenides, arsenides, phosphides, nitrides, carbon, and carbides. Toward the end, we highlight a range of innovative applications enabled by the unique combination of different potential properties of inorganic nanobelts. Continued development of the synthesis strategies and the preparation procedures as well as functionalization of nanobelts for novel applications will provide significant breakthroughs.
Metal Oxide Nanoparticles
Authors: Fernández‐García Marcos , Rodriguez José A.
Published: December 2011

This article covers the fundamental science, synthesis, characterization, physicochemical properties, and applications of oxide nanomaterials. It also explains the fundamental aspects that determine the growth and behavior of these systems, briefly examines synthetic procedures using bottom‐up and top‐down fabrication technologies, discusses the sophisticated experimental techniques and state‐of‐the‐art theory results used to characterize the physicochemical properties of oxide solids, and describes the current knowledge concerning key oxide materials with important technological applications.
Nanoporous Metal Phosphonates
Authors: Miller Stuart R. , Wright Paul A.
Published: December 2011

Nanoporous metal phosphonates make up a growing family of organic–inorganic hybrid solids, which extends the scope of functional materials with potential in adsorption, ion exchange, catalysis, and sensing. Their attributes include thermal stability and the ability to incorporate functional organic and inorganic components accessible to adsorbates. The best established are those based on zirconium, comprising layered solids in which organic groups act as pillars between inorganic zirconium phosphate sheets. The porosity, which can be on the micro‐ or mesoscale, is engineered by design of the organic pillars and their number density and, while not ordered on the long range, can have a narrow distribution. Other pillared layered metal phosphonates are also known. More recent developments have yielded framework metal phosphonates with well‐defined permanent microporosity similar to that observed in zeolites, in the 0.3–1‐nm range, that demonstrate molecular sieving. Currently, the most promising solids of this kind include aluminum methylphosphonates and metal bisphosphonates, which can be described as
metal–organic frameworks
or MOFs. Another area of smaller, but developing interest is the preparation of metal phosphonates with ordered mesoporosity, in which a wide range of solids with relatively narrow distribution of pore sizes in the 3–15‐nm range is prepared by surfactant‐templated approaches. These have potential in the interaction with large molecules, including proteins.
Nano/Microporous Materials: Nanostructured Layered Double Hydroxides
Authors: Leroux Fabrice , Prévot Vanessa
Published: December 2011

This review summarizes developments in nanostructured layered double hydroxide (LDH) materials for the period 2004–2007. Particular attention is paid to synthesis aspects, including coprecipitation, urea decomposition, sol‐gel processing and derivative methods as well as the generation of functional materials through delamination either from solvent solution or in situ within a polymer. Coating processes, illustrated by the heterogeneous growth of nanorods onto LDH surfaces, is distinguished from particle nanostructuration. In addition, nanostructuration from LDH frameworks is described for iron‐based oxides and other metal oxides in which catalytic, magnetic, or energy‐storage properties are discussed. Other examples of nanostructuration, such as complex encapsulation, are demonstrated not only with different complexes, such as polyoxometallates and porphyrines but also with rare earth and quantum dot materials, where interest is focused on luminescent and optical properties. Additionally, drug encapsulation and/or release, gene‐reservoir applications, and incorporation of DNA and bioinorganic enzymes into LDH assemblies nicely illustrate biologically related uses of LDH nanoplatelets. Finally, reactions occurring within LDH interlayer spaces are described, and the role of LDH framework as a nanoreactor is illustrated by in situ polymerization of conjugated polymers and thermoplastics. LDH materials can also be used as sacrificial templates for fabricating nanosized polymers and for the synthesis of carbon replica and carbon fibers.
Nanocomposite Materials: Semiconductors in Zeolites
Authors: Goldbach Andreas , Saboungi Marie‐Louise
Published: December 2011

Encapsulation in zeolites holds considerable promise for organizing semiconductor quantum dots and quantum wires into ordered two‐ and three‐dimensional arrays that can be used in a variety of applications. While the use of such materials has been limited until now by a number of practical difficulties, considerable progress has been made in the last few years in surmounting these obstacles. This article reviews recent progress in the field, particularly with regard to stabilization of the nanocomposites against moisture, modulation of their properties by appropriate cation substitution, and preparation of materials in the form of thin films that can exhibit strong nonlinear optical activity. Finally, the article discusses the present perspectives for the field and outlines some research directions that must be pursued for these materials to achieve their full range of potential applications.
Molecular and Supramolecular Arrays of the [
Re
6
(μ
3
‐
Se
)
8
]
2+
Core‐Containing Clusters
Authors: Zheng Zhiping
Published: December 2011

Transition metal clusters are a unique class of chemical substances. Not only do they have well‐defined molecular structures, they also exhibit interesting and potentially useful properties that are inherent to metal–metal bonded species. In this contribution, our efforts in developing synthetic methodologies necessary to bring a cluster system out of the limited sphere of fundamental cluster chemistry and into general synthetic applicability are summarized. Specifically, we have explored the uses of site‐differentiated cluster complexes of the [Re
6
(μ
3
‐Se)
8
]
2+
core as stereospecific building blocks for supramolecular construction. A great variety of cluster‐supported molecular and supramolecular architectures have been realized. These include Tinkertoy‐like molecular cluster arrays featuring cluster units bridged by multitopic ligands and supramolecular assemblies of clusters engineered via hydrogen bonding and metal–ligand coordination. Some of these nanoscopic cluster‐containing systems display rather interesting electronic and spectroscopic properties and, therefore, hold great potential in developing molecule‐based electronic and optical materials. The work therefore marks the beginning of what promises to be an exciting new chapter in cluster chemistry.
Nanostructured Catalysts: Controlling Single‐Site Composition
Authors: Barnes Craig E. , Mayes Richard T.
Published: December 2011

Developing well‐understood methodologies for the preparation of single‐site catalysts has long been a goal in catalysis science. Newly emerging strategies for preparing and functionalizing nanostructured materials open the door to a number of new approaches that address this goal. General, structural, and chemical definitions of nanostructured, single‐site catalysts are presented, and the challenges associated with meeting these requirements are discussed. Selected examples of nanostructuring strategies that lead to well‐defined single‐site catalysts are described.
Endohedral Fullerenes
Authors: Yang Shangfeng , Dunsch Lothar
Published: December 2011

The recent state in endohedral fullerenes is reviewed in terms of both sides of the fullerene: the new carbon cages including non‐IPR (IPR, isolated pentagon rule) structures as well as new species encaged in the inner fullerene void. A general principle is valid nowadays and used in endohedral fullerene research: the stabilizing ability of the encaged structure for the fullerene cage architecture and that of the fullerene cage for the encaged species. Thus, the cage size ranges from C66, the first non‐IPR fullerene cage, to C100while the encaged species are extended up to five atomic clusters as for Sc3C2. The world of endohedral fullerenes was significantly enlarged within the past seven years by the cluster fullerenes containing structures like the M3N nitrides. This review is focused on the new development of this amazing world of carbon nanostructures since 1999, including new structures, properties, and potential applications of endohedral fullerenes as well as prospects.
Inorganic Nanomaterials Synthesis Using Liquid Crystals
Authors: Boissière Cédric , Grosso David , Prouzet Eric
Published: December 2011

Soft matter offers a unique property that combines high order with specific geometry and high dynamics that allows this geometry to adapt easily to rapid changes in physicochemical parameters. This property has been used in many systems for the formation of nanostructures when a soft matter such as liquid crystals acts as a mold that can be easily tuned and also removed once the material has been synthesized. In this review, we describe the general bases of the mechanisms that lead to nanostructured materials. Specific emphasis is given on the evaporation‐induced self‐assembly (EISA) method, where a liquid crystal is obtained upon drying of a complex solution during evaporation in a thin film. We also describe how surface micropatterning can be obtained by coupling solid‐state chemistry and soft matter and perspectives based on versatility of liquid crystals.
Biomimetic Chemistry of Hybrid Materials
Authors: Rurack Knut , Martínez‐Máñez Ramón
Published: December 2011

The article discusses representative examples published in the field of functional biomimetic chemistry of hybrid materials between 2004 and mid‐2007. First, we focus on the modification of morphological aspects of (bio)organic–inorganic hybrid materials to create sophisticated gating and switching mechanisms. The architecture of the systems is presented and the elements of control by external stimuli that have been established in recent years, such as optical, electrochemical, chemical, thermal, or magnetic means, are described. Various functions ranging from (site‐specific) delivery to indication at the nanometric level are reported. Next we develop the idea of utilizing hybrid frameworks for biomimetic signaling inspired by the way nature has created binding pockets and the concept of induced‐fit. Such a merging of inorganic scaffolds with supramolecular concepts results in enhanced molecular recognition and signaling. Finally selected recent advances in the field of hybrid biomimetic motors both of linear and rotary types are presented. The contribution shows how novel biomimetic functions can arise from synergisms between specifically designed hybrid materials and the implementation of supramolecular and/or bioorganic concepts.
N‐Heterocyclic Carbene‐Containing Metal Complexes
Authors: Fantasia Serena , Clavier Hervé , Nolan Steven P.
Published: December 2011

In the last decade, coordination chemistry has witnessed the advent of a new class of ligands: theN‐heterocyclic carbenes (NHCs). The “success story” associated with this ligand family can be explained by the unique stereoelectronic properties of the NHCs; these unique properties have led to their numerous applications in catalysis. This article provides an overview of developments and recent advances in the syntheses of NHCs and NHCtransition metal complexes. For these NHC ligand‐containing complexes, an analysis focuses on stability and reactivity patterns is provided. Reactions such as the cleavage of NHCmetal bond, CH and CC activations, NHC migration, and NHC insertion are presented.
Medicinal Inorganic Chemistry: Continuum of Dose versus Response—From Deficiency through Optimal Intake to Toxicity
Authors: Thompson Katherine H.
Published: December 2011

Metal‐ion essentiality is not a static concept. Over the course of the last several decades, essentiality has been redefined to broaden the definition beyond “necessary to support human life” to include “having a defined biochemical function.” The main effect of this redefinition has been to restrain the addition of additional ultratrace elements, present in the human body, but not clearly required in a specific amount in the daily nutrient intake, to the ever‐expanding list of known essential elements. Essential metal ions are associated not only with recognizable deficiency symptoms under conditions of inadequate intake but also with existing homeostatic mechanisms that regulate absorption, distribution, storage, and excretion of the metal‐ion in vivo. The Bertrand diagram is a schematic representation of the range of essential metal‐ion intake consistent with optimal nutrient intake, bounded on the lower intake range by deficiency symptoms and on the upper intake end, by increasingly severe toxicity symptoms. The continuum of dose versus response includes both tails of this spectrum for all essential metal ions. Not all metal ions are the same: each has an appropriate “window of optimal intake” whose width and concentration ranges vary widely from one metal ion to the other.
Medicinal Inorganic Chemistry: Metallotherapeutics for Chronic Diseases
Authors: Thompson Katherine H.
Published: December 2011

Metal‐containing therapeutic agents designed for use in chronic disorders, such as gastrointestinal dyspepsia, bipolar disease, diabetes mellitus, osteoporosis, and arthritis, present additional challenges to the medicinal chemist. Beyond the immediate toxicity issues seen with acute disease treatments, chronic use of metallotherapeutic agents may result in metal ion accumulation or in gradually developing intolerance that can require discontinuation of the drug. Metallotherapeutic agents that have passed the rigorous testing required for chronic use include bismuth subsalicylates, for a variety of gastrointestinal disorders; lithium carbonate, for bipolar disease; lanthanum carbonate, for end‐stage renal disease; strontium ranelate, for osteoporosis; and the gold‐based antiarthritic, Auranofin™, although the last has fallen out of favor. Chromium picolinate is an approved nutritional supplement, a designation that allows less stringent testing than for new chronic‐use drugs. Among those compounds not currently approved for clinical use, but showing promise, the copper – indomethacin and zinc – indomethacin complexes, for inflammation resulting from rheumatoid arthritis; vanadium compounds, for glucose‐ and lipid‐lowering in type 2 diabetes mellitus; and selenium compounds, as possible cancer preventatives, are worthy of consideration.
Medicinal Inorganic Chemistry: Sequestration or Removal in Metal Ion Overload Disorders
Authors: Thompson Katherine H.
Published: December 2011

All metal ions, whether essential or nonessential, are toxic when present in excess. Metabolic disorders in which metal ion overload is a key contributing factor include hemochromatosis, β‐thalassemia, Wilson's disease, Menkes syndrome, and Friedreich's ataxia. For some metal ions, overload conditions may come about as a result of excess oral, inhalation, or dermal exposure. In order to correct a metal ion overload condition, an appropriate ligand choice may speed up the elimination or safely sequester the excess metal ion, and may be the treatment of choice. A number of effective chelating agents are discussed, including desferrioxamine, deferiprone,D‐penicillamine, and copper– histidine chelate. Marginal overload conditions may lead to marginal deficiency of another metal ion, a result, paradoxically, from single metal ion supplementation. An example would be marginal iron overload, resulting from iron supplement use in excess of need, which leads to marginal manganese deficiency. Such effects are due to metal ion interaction effectsin vivo.
Spectroscopic Properties Obtained from Time‐Dependent Density Functional Theory (TD‐DFT)
Authors: Autschbach Jochen
Published: December 2011

This article summarizes basic aspects of time‐dependent density functional theory (TD‐DFT) and its applications in inorganic chemistry. Sections titled TD‐DFT and Spectroscopic Properties outline some of the theoretical formalism and explain how excitation energies can be obtained from TD‐DFT linear response theory. Common approximations in density functional theory (DFT) exchange‐correlation (XC) potentials that might have adverse effects on the accuracy of computed results are explained. Sections titled Benchmark Data and Some Case Studies discuss a number of case studies, with emphasis on TD‐DFT excitation spectra computations in coordination chemistry. Computations of spectra and other properties of metals clusters are also discussed. Apart from excitation spectra, this section also describes TD‐DFT computations of Raman intensities (including resonance Raman and surface‐enhanced Raman spectra (SERS)), magnetic circular dichroism, optical rotatory dispersion (CD and ORD), and concludes with some comments on relativistic effects.
Spectroscopic Properties of Protein‐Bound Cofactors: Calculation by Combined Quantum Mechanical/Molecular Mechanical (
QM
/
MM
) Approaches
Authors: Sundararajan Mahesh , Riplinger Christoph , Orio Maylis , Wennmohs Frank , Neese Frank
Published: December 2011

In this article, we discuss some aspects of the combined quantum mechanics/molecular mechanics (QM/MM) method for the calculation of energetics and spectroscopic parameters of protein‐bound cofactors. Following a brief introduction to the theory of the QM/MM approach, some selected examples are discussed that illustrate the use of this methodology in theoretical spectroscopic studies. The examples cover the following: (i) excitation energies for the
S
0
 → 
S
1
transition in bacteriorhodopsin; (ii) electron paramagnetic resonance (EPR) and absorption spectra of plastocyanin; and (iii) the spin Hamiltonian parameters of compound I in cytochrome
P
450
cam
.
Quantum Mechanical/Molecular Mechanical (
QM
/
MM
) Methods and Applictions in Bioinorganic Chemistry
Authors: Ryde Ulf
Published: December 2011

The combination of quantum mechanics and molecular mechanics (QM/MM) methods is a promising approach to study the structure, function, and properties of proteins. The number of QM/MM applications on metalloproteins has been steadily increasing and it is the method of choice to study the influence of the protein onto the structure, spectroscopy, and energetics of an active site. In particular, it has been shown that QM/MM calculations can provide geometries of metal sites in proteins with an accuracy that is better than in low‐ and medium‐resolution crystal structures. However, it is quite hard to obtain reliable and converged energies. Therefore, QM/MM is still an area of method development and no consensus of the best treatment of a protein has yet been reached. This review covers various aspects of QM/MM studies of metalloproteins, including methods to incorporate experimental data in the calculations, methods to obtain reliable energies, as well as some examples of typical applications.
Computational Studies: Proton/Water Coupling to Metals in Biological Reaction Mechanisms
Authors: Bu Y. , Cukier R. I.
Published: December 2011

Metalloenzymes promote a wide variety of reaction chemistry with the use of protons and water, and associated ligands and protein residues. The charges/oxidation states of the metals and many charged and/or highly polar residues and ligands produce strong effects on acid‐base‐driven chemistry. Computational approaches to metalloenzyme mechanisms require a compromise between accuracy (use of high‐level quantum chemical methods) and the ability to handle many atoms (use of force field methods). Methods that divide the system into a part that is treated accurately and a part treated at a lower level require careful attention toward the chemistry of the specific system. In this article, we outline a number of our recent approaches to some enzymatic reactions where metals, protons, and water are intimately coupled. Three metalloenzymes, cytochrome c oxidase, cytosine deaminase, and calcium ATPase (a calcium pump), are discussed using methods that divide an enzyme into a reaction zone treated at a high level and the remainder treated at a lower level.
Computational Studies:B12Cofactors and their Interaction with Enzyme Active Sites
Authors: Brunold Thomas C.
Published: December 2011

Cyanocobalamin, commonly known asvitamin B12, and its biologically active derivatives, 5′‐deoxyadenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl), have long fascinated scientists with their elaborate structures and intriguing reactivities in enzymatic systems. While the large size and complex electronic structures of these cofactors have posed a major challenge for theoretical chemists, recent insights gained from kinetic, spectroscopic, and X‐ray crystallographic studies have established an excellent foundation for validating computational investigations of the geometric, electronic, and reactivity properties of the isolated cofactors and the molecular details of the catalytic cycles of B12‐dependent enzymes. This review—which is by no means exhaustive—summarizes salient information that has been obtained from experimentally validated computational studies of the following: (i) the free B12cofactors in their Co3+, Co2+, and Co1+oxidation states; (ii) the mechanism by which enzymes involved in the biosynthesis of AdoCbl overcome the large thermodynamic barrier associated with the Co2+ → Co1+reduction; (iii) plausible strategies by which AdoCbl‐dependent enzymes achieve a trillion‐fold rate of acceleration for thehomolyticcleavage of the cofactor's CoC(Ado) bond; and (iv) the means by which MeCbl‐dependent methyltransferases regenerate the active MeCbl cofactor and accelerate the rate of methyl transfer viaheterolyticCoC(Me) bond cleavage by as many as 6 orders of magnitude.
Electronic Structure Calculations: Transition Metal—
NO
Complexes
Authors: Ghosh Abhik , Hopmann Kathrin H. , Conradie Jeanet
Published: December 2011

The advent of density functional theory led to a major exploration (and, in some cases, a reexploration) of key aspects of transition metal nitrosyls. Many of these developments are reviewed here for the first time, with comparable emphasis placed on both heme/metalloporphyrin and nonheme systems. The latter exhibit diverse electronic structures, which we have described in some depth. Several of the open‐shell species described exhibit broken‐symmetry electronic structures, with significant spatial separation of majority and minority spin densities.
Computational Methods: Heteropolyoxoanions
Authors: Poblet Josep M. , López Xavier
Published: December 2011

Possibly no other class of organic or inorganic compounds displays more versatility than polyoxometalates (POMs) (or polyoxoanions) with respect to electronic and molecular structures, properties, and applications. POMs attract the attention of scientists from many fields, such as catalysis, materials science, and medicine. More recently, POMs have also attracted the interest of computational chemists. This article describes some of the most relevant electronic properties for several of the most representative heteropolyoxoanions, such as the so‐called Keggin [XM
12
O
40
]

n
−

, Dawson [X
2
M
18
O
62
]

m
−

, and Preyssler [XP
5
W
30
O
110
]

q
−

anions. Density functional theory (DFT) methods have proven to be useful for the rationalization of many properties of POMs. In this article we illustrate some of them, often using the simple language of molecular orbitals.
Computational Methods: Lanthanides and Actinides
Authors: Dolg M. , Cao X.
Published: December 2011

First‐principles and semiempirical relativistic quantum chemical methods applicable to molecular systems containing lanthanides and actinides are briefly reviewed. Selected recent applications of some of these methods are discussed.
Nuclear Magnetic Resonance (NMR) Parameters of Transition Metal Complexes: Methods and Applications
Authors: Kaupp Martin , Bühl Michael
Published: December 2011

This article provides an overview of first‐principle computations targeted at nuclear magnetic resonance (NMR) properties of transition‐metal complexes. Recent methodological developments and illustrative applications are highlighted, all of which are rooted in density functional theory (DFT). Special attention is called to chemical applications of such NMR computations, ranging from structure elucidation of metalloenzymes to detailed interpretation of NMR spectra of paramagnetic compounds.
Noble Gas Compounds: Reliable Computational Methods
Authors: Dixon David A.
Published: December 2011

Because of the general interest in the bonding in noble gas (Ng) compounds and the lack of experimental data coupled with large discrepancies, reliable theoretical calculations are very important for the prediction of their structures and thermodynamics. We describe an approach for the prediction of heats of formation to ±1 kcal mol−1(chemical accuracy) based on molecular orbital theory level using coupled cluster (CCSD(T), coupled cluster with single and double excitations plus a perturbative triples correction) theory extrapolated to the complete basis set (CBS) limit with the correlation‐consistent basis sets including relativistic effective core potentials (RECPs). Additional corrections to the valence correlation energies include core–valence (CV) correlation, molecular scalar relativistic corrections, atomic spin–orbit corrections, and zero‐point vibrational energies. Applications of this approach for the determination of the structure of XeF6, the heats of formation of the xenon fluorides and krypton fluorides, and the methyl cation affinities (MCAs) of the Ngs are described. XeF6is predicted to have C3vsymmetry only at the highest computational levels. The experimental heats of formation of XeF4and XeF6require significant revision. The predicted heats of formation for KrF4and KrF6show that it will be extremely difficult to synthesize these compounds. The calculations show that there are serious issues with the experimental MCAs of all of the Ngs except for Ne.
Spin‐Orbit Coupling: Effects in Heavy Element Chemistry
Authors: Kaltsoyannis Nikolas
Published: December 2011

Starting from the premise that the chemical consequences of scalar relativistic effects are by now largely understood, and may be incorporated more or less routinely into quantum chemical calculations, this contribution focuses on the historically less widely investigated part that spin‐orbit coupling plays in heavy element electronic structure. The effects of relativity are first summarized, followed by a discussion of the principal approaches to the calculation of molecular electronic structure and how relativistic effects may be incorporated into them. Two approaches for the calculation of spin‐orbit coupling effects are then presented; namely, the spin‐orbit coupled time‐dependent density functional theory technique of Wang
et al
. [Wang, F.; Ziegler, T.; van Lenthe, E.; van Gisbergen, S.; Baerends, E. J.
J. Chem. Phys.
2005
,
122
, 204103] and the spin‐orbit restricted active space state interaction method of Roos and coworkers [Roos, B. O.; Malmqvist, P. A.
Phys. Chem. Chem. Phys.
2004
,
6
, 2919]. Recent applications of both approaches to the electronic structure of p, d, and f block systems are then discussed, with emphasis on the improved understanding and agreement with experiment that these methods yield.
Computational Studies: Chemical Evolution of Metal Sites
Authors: Jensen Kasper P.
Published: December 2011

The structures of naturally occurring metal sites have evolved over hundreds of millions of years to perform complex functions under very specific biological and nonbiological constraints. Modern computational chemistry has now reached a level of accuracy that allows us to study the full significance of molecular evolution by systematically altering the components of the native metal sites and by monitoring the resulting effects on relevant computed properties. This procedure, referred to as
computational chemical evolution
, not only explains the use of certain metal ions as opposed to others in metalloproteins, but also lends promise to the design of new multifunctional metal sites that are no longer restricted by biological constraints, to be used in medicine and catalysis.
Tritium: Radionuclide
Authors: Galeriu Dan , Melintescu Anca
Published: December 2011

Tritium is the heavy isotope of hydrogen and can therefore participate directly in a wide range of biological functions. It is formed through natural processes but is also generated through human activity in nuclear reactors, fusion, and weapons. In addition, it has some commercial applications. Its occurrence, chemical and physical properties, and speciation are unique in comparison to other radionuclides. This article summarizes what is currently known about tritium with regard to the isotope's occurrence, chemistry, speciation, remediation, separation, and the analytical techniques used for its detection and quantification. The potential impact of tritium on human health is also described.
Cesium: Radionuclide
Authors: Lima Enrique
Published: December 2011

Radionuclides of cesium are generated mainly from nuclear fission. Many cesium radionuclides are known, but
134
Cs and
137
Cs are of the greatest concern because of their radiological properties. Cesium is present in polluted effluents of nuclear power plants. Gas, liquid, and solid wastes contaminated with cesium can be found but aqueous effluents, where cesium is present in the cationic form, are the most common. These cations can reach agricultural fields due to their high affinity for clays. Thus, cesium radionuclides can be incorporated into the food chain, and ultimately transported to human beings.
Strontium: Radionuclides
Authors: Guillén Francisco Javier , Baeza Antonio , Salas Alejandro
Published: December 2011

Strontium has several radioactive isotopes, with90Sr being the most important in the environment. This radionuclide dispersed worldwide as a consequence of the atmospheric nuclear weapon tests in the 1960s, and is locally enhanced owing to the accidents involving radioactive material.90Sr is a pure β‐emitter and it may be detected by several detection techniques (gas‐flow proportional, liquid scintillation, Cerenkov counting, and ICP‐MS), after an appropriate radiochemical separation. The environmental behavior of radiostrontium is governed by its chemical similarities to calcium. It is usually associated with the mobile and bioavailable fractions in soils, and with the low MW fraction in aquatic ecosystems. The potential human exposure to radiostrontium is mainly due to the ingestion of food, milk and cereals being the two major sources. This exposure can be reduced to some extent by the addition of calcium fertilizers to minimize the soil‐to‐plant transfer of radiostrontium, and by increasing cattle calcium intake to decrease the90Sr content in milk.
Radium: Radionuclides
Authors: Vandenhove Hildegarde , Verrezen Freddy , Landa Edward R.
Published: December 2011

This article describes (1) the occurrence, chemistry, and bioavailability of radium (Ra) in terrestrial and aquatic environments, and its analysis in environmental samples, (2) the nature of naturally occurring radioactive materials (NORM) and their role in radium‐contamination scenarios, and (3) the geochemical processes and remedial measures associated with radium‐contaminated water and soil. Radium is the heaviest of the Group II, alkaline earth metals. Radium is exclusively divalent and its chemistry resembles that of barium. Radium has a limited environmental mobility due to sorption (e.g., by hydrous oxides of Fe, Mn, and Al) and coprecipitation reactions (e.g., with barite).

All isotopes of radium (atomic number 88) are radioactive. The most important radium isotopes are226Ra (half life 1600 years) and228Ra (half life 5.7 years), decay products of, respectively, the238U and the232Th series. As members of natural radioactive decay series, these radium isotopes are found in uranium‐ and thorium‐bearing minerals. Concentrations of uranium and thorium in rocks can range from those of ore‐grade deposits to the trace levels typical of common rock‐forming minerals.

In uncontaminated surface waters, radium content is generally low and within a narrow range (0.5–20 mBq l−1). Radium in groundwater is highly variable (<0.52–55 000 mBq l−1) and can arise from natural sources, resulting from the interaction of groundwater with radium‐bearing materials or indirectly from man's exploitation of the radioactive minerals of uranium and thorium. The major challenge associated with many NORM‐containing residues or NORM‐contaminated sites is the larger volumes of material and the relatively low specific activities.
Phosphorus: Radionuclides
Authors: Kim Kibong , Churchill David G.
Published: December 2011

32P and33P are important radionuclides of phosphorus with half‐lives of 14.3 and 25.3 days, respectively, and which decay via β−emission. These isotopes (of 23 known) have anthropogenic sources and are prepared by the enrichment of sulfur. The radionuclides are used in tracer studies primarily as phosphate, or other common phosphate forms such as “phosphate rock” or ortho‐phosphoric acid. Various labeling and therapeutic studies have been performed in the fields of biology, botany, and in clinical medicine and are mentioned herein. Radioisotopes of phosphorus can be detected by liquid scintillation counting. There is, however, limited knowledge about remediation as32P and33P are short‐lived.
Thallium: Radionuclides
Authors: Wehmschulte Rudolf J.
Published: December 2011

Of the 35 radioactive isotopes, only201Tl and204Tl with half‐lives of 73 h and 3.78 y are applied in medicine and materials analysis. Both are usually generated in situ on site in small amounts just prior to use in cyclotrons. Owing to the small amounts applied and generated, they are of minor concern as environmental radionuclides despite their high mobility under physiological and environmental conditions.