bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neutron Diffraction
Authors: Yousufuddin Muhammed , Bau Robert 
Published: December 2011

AbstractThe following article reviews the technique of neutron diffraction and its effectiveness in probing materials of chemical interest. The main advantage of neutrons is their ability to detect hydrogen atoms. We describe in this article several examples where neutrons offered additional information that was otherwise unavailable from X‐rays. We have summarized a number of structures studied using neutron diffraction. Most of these structures showed the precise location of chemically interesting hydrogen atoms. We have also summarized structures where neutron diffraction allowed for the assignment of absolute stereochemistry in deuterated systems. Lastly, we have discussed the usefulness of neutron diffraction in protein crystallography.One of the major disadvantages of neutron diffraction is the immensely low number of neutron sources available as compared to X‐ray sources. We have detailed the neutron sources around the world capable of neutron diffraction experiments, including sources that are currently under construction such as the Spallation Neutron Source in Oak Ridge, TN and J‐PARC in Tokyo, Japan. In addition, a number of neutron diffraction instruments and their sample requirements are illustrated.In the past, neutron diffraction has been overlooked by most practicing chemists as an efficient analytical tool. However, with the newer more powerful facilities and instrumentation in development, chemical systems studied with neutrons should become more common.
Nuclear Magnetic Resonance (NMR) Spectroscopy of Inorganic/Organometallic Molecules
Authors: Iggo Jonathan A. , Liu Jianke , Khimyak Yaroslav Z. 
Published: December 2011

AbstractNMR spectroscopy is an indispensable spectroscopic tool for the characterization of inorganic compounds. This contribution provides a guide to the application of recent advances in high‐resolution, solid‐state, and high‐pressure NMR spectroscopic methods to organometallic/inorganic molecules and solids. The topics covered include methods for the determination of structure, intermolecular interactions, solid‐state organization, reaction kinetics, and diffusion.
Nuclear Quadrupole Resonance (NQR) Spectroscopy
Authors: Wulfsberg Gary P. 
Published: December 2011

AbstractThe article concerns the usefulness of nuclear quadrupole resonance (NQR) spectroscopy in inorganic and organometallic chemistry. NQR‐active nuclei have spinI ≥ 1; those of high enough abundance to be commonly useful are found in the odd‐numbered groups of the periodic table. These are tabulated and examples given for each. The number of NQR frequencies observed in a solid‐state compound reflects the number of chemically different quadrupolar atoms in the compound and also the number of crystallographically inequivalent atoms; changes in the latter may indicate phase transitions or different polymorphs of a given compound. More commonly, one uses average NQR frequencies for chemically different atoms, and from these average frequencies, derives atomic parameters such as populations of valence orbitals, partial ionic charges, π‐bond orders, and covalent bond orders of the quadrupolar atom. The article mainly reviews selected applications of halogen (35Cl,79, 81Br,127I) NQR to specific bonding questions in inorganic chemistry, and divides these according to whether the halogen or other atoms are (a) single bonded, (b) single bonded but with secondary bonds with other atoms, or (c) bonded to several atoms. For singly bonded atoms, the applications reviewed include (a1) relativistic effects, (a2) effects of nearby ionic charges on haloacetate ions, (a3) the contrasting effects of nearby ionic charges on halometallate ions, (a4) effects of intramolecular partial charges on chlorines in organosilicon compounds, (a5) cis‐and trans‐ ligand effects in substituted halometallate complexes, and (a6) interpretations of multicentered bonding in trihalide ions. Secondary bonding of single‐bonded halogen atoms are reviewed particularly in the cases of (b1) halocarbons as ligands, (b2) chloroacetates and chlorophenolates as chlorine‐donor ligands, and (b3) in salts of weakly coordinated halogenated anions. Finally, some illustrations are given of NQR studies of central multicoordinated atoms (for example, transition‐metal atoms in complexes).
Nuclear Resonance Vibrational Spectroscopy (
NRVS
)
Authors: Zeng Weiqiao , Silvernail Nathan J. , Scheidt W. Robert , Sage J. Timothy 
Published: December 2011

Abstract
Nuclear Resonance Vibrational Spectroscopy (NRVS) utilizes the simultaneous excitation of the Mössbauer nucleus and vibrational quanta. Vibrational features appear as sidebands on the recoilless resonance. NRVS reveals the complete vibrational spectrum of the probe nucleus with the resolution almost equal to that of Raman or infrared. Major advantages include selectivity to vibrations of the Mössbauer isotope with quantitative information on vibrational amplitudes, as well as frequencies. Single crystal measurements are selective for motion along the exciting X‐ray beam. NRVS is equally applicable to all ligation and oxidation states. Questions that can be addressed include the strength of metal coordination, the energetic cost of probe displacement, discrimination of metal‐ligand vibrations from cofactor or peptide vibrations, and the local vs. global character of active site vibrations.
Photoelectron Spectroscopy
Authors: Gruhn Nadine E. , Lichtenberger Dennis L. 
Published: December 2011

Abstract
Photoelectron spectroscopy measures the energies for emission of electrons from molecules or materials through application of the photoelectric effect. For neutral molecules this is a direct measure of the ionization energies. The ionizations are explicitly defined in terms of transitions between the ground state of a molecule and accessible states of the molecular positive ion, but in a first order approximation, each ionization of a molecule can be described as removal of an electron from an individual orbital. The ionization energies can then be considered as measures of orbital energies, and shifts can be interpreted in terms of orbital stabilizations or destabilizations due to changes in electron distributions and bonding. The intensities and profiles of the ionization bands in the photoelectron spectra provide additional information on the characters and bonding natures of the orbitals. All orbitals can be probed, from valence orbitals such as lone pairs and bonds to orbitals in the cores of heavy atoms. Photoelectron spectroscopy is a large field of study that has many subfields and new techniques continue to be introduced. These different subfields all have different instrumental and sample constraints, but taken as a whole photoelectron spectroscopic experiments can be performed on almost any system of interest in inorganic chemistry. This article summarizes the basic physical principles of photoelectron emission caused by one or more photons, the relationship of photoelectron spectra to the electronic structure of neutral and anionic molecules, and the additional considerations for photoionization of bulk samples. Auger electron spectroscopy (AES) and Penning ionization electron spectroscopy (PIES), techniques which are closely related to photoelectron spectroscopy, are also discussed. Case studies are given for applications of photoelectron spectroscopy to study of bioinorganic model complexes, including iron‐sulfur and molybdenum‐sulfur bonding and covalency, electronic structure of porphyrins and metalloporphyrins, negative‐ion photoelectron spectroscopy of phthalocyanines, and the use of the technique to measure inner‐sphere reorganization energies.
ResonanceRaman Spectroscopy
Authors: Czernuszewicz Roman S. , Zaczek Marzena B. 
Published: December 2011

AbstractResonance Raman (RR) spectroscopy is an invaluable and widely used probe of structure and bonding for chromophoric transition metal centers in proteins and enzymes. The spectacular increase in detection sensitivity and selectivity of RR spectroscopy for vibrations that are localized in the absorbing center(s) of the molecule has revolutionized the vibrational spectroscopic field of bioinorganic systems. In this article, we explain the characteristics of RR spectra, emphasizing the kind of information that can be obtained and the rules for optimal resonance enhancement. We then discuss the applications of RR scattering to the study of structural dynamics of two different mononuclear metal‐cysteinate sites, type‐1 copper in cupredoxins and Fe(S‐Cys)4center in rubredoxins, using a combination of site‐directed mutagenesis, production of isotopically labeled proteins, and cryogenic‐temperature RR methods. These chromophores, involved in biological electron transport, have been very suitable subjects for RR studies because they exhibit strong absorption bands in the visible region due to (Cys)S → Cu(II) (∼625 nm) and (Cys)S → Fe(III) (∼500–570 nm) charge‐transfer electronic transitions that facilitate the observation of resonantly enhanced Cu‐and Fe‐thiolate vibrations.
X‐Ray Absorption Spectroscopy
Authors: Bencze Krisztina Z. , Kondapalli Kalyan C. , Stemmler Timothy L. 
Published: December 2011

Abstract
X‐ray absorption spectroscopy (XAS), often referred to as X‐ray absorption fine structure (XAFS) spectroscopy, is a powerful technique available for determining the local coordination site structure and electronic properties of specific atoms in molecules. XAS can be performed on molecules in the gaseous, solution, or solid states, and generally every element is spectroscopically active. This technique utilizes high intensity X rays supplied by synchrotron radiation sources to selectively excite core electron transitions for a specific element of choice. XAS spectra are divided into two spectral regions, the X‐ray absorption near edge structure (XANES) region and the extended X‐ray absorption fine structure (EXAFS) region. XANES spectra can be utilized to provide: (1) qualitative information regarding the ligands coordinated to the absorbing atom, (2) semi‐quantitative information regarding the redox state of the absorbing atom, and (3) metal‐ligand coordination geometry. Simulations of the EXAFS data can provide information regarding absorber‐scatterer bond length values to extremely high accuracy (ca. ±0.02 Å), as well as coordination numbers and ligand identity at reduced accuracies. The high accuracy in bond lengths achieved from XAS makes this technique extremely sensitive for measuring subtle structural perturbations within molecules under perturbed or turnover conditions. When utilized with other techniques, XAS can supply the metrical parameters required to understand the chemical properties of specific elements in a molecule.
X‐Ray Powder Diffraction
Authors: Clearfield Abraham , Bhuvanesh Nattamai 
Published: December 2011

AbstractCrystalline 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

Abstract
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

AbstractThis 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

Abstract

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

AbstractIn 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

Abstract
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

Abstract
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

AbstractIn 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

AbstractCancer 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.