A. Water Exchange 2326 B. Proton Exchange 2327 C. Electronic Relaxation 2327 D. Relaxivity 2331 E. Outerand Second-Sphere Relaxivity 2334 F. Methods of Improving Relaxivity 2336 V. Macromolecular Conjugates 2336 A. Introduction 2336 B. General Conjugation Methods 2336 C. Synthetic Linear Polymers 2336 D. Synthetic Dendrimer-Based Agents 2338 E. Naturally Occurring Polymers (Proteins, Polysaccharides, and Nucleic Acids) 2339

https://mriquestions.com/uploads/3/4/5/7/34572113/lauffer_1999_review.pdf

Gadolinium(III) Chelates as MRI Contrast Agents: Structure, Dynamics, and Applications

4. Structure of Ionic Hydration Shells 1351 4.1. Results from Diffraction Experiments 1351 4.1.1. X-ray Diffraction 1351 4.1.2. Neutron Diffraction 1351 4.2. Results from Computer Simulations 1352 4.3. Results from Spectroscopic Measurements 1354 4.3.1. Vibrational Spectroscopic Measurements 1354 4.3.2. EXAFS Spectroscopy 1354 4.3.3. NMR Relaxation Studies 1355 4.3.4. Dielectric Relaxation Studies 1355 4.4. Summary of the Structure of Ionic Hydration Shells 1355

Effect of ions on the structure of water: structure making and breaking.

Theoretical Methods for the Description of the Solvent Effect in Biomolecular Systems.

The characteristics of pre-edge peaks in K-edge x-ray absorption near edge structure (XANES) spectra of 3d transition metals were reviewed from viewpoints of the selection rule, coordination number, number of d-electrons, and symmetry of the coordination sphere. The contribution of the electric dipole and quadrupole transition to the peaks was discussed on the basis of the group theory, polarized spectra, and theoretical calculations. The pre-edge peak intensity for Td symmetry is larger than those for Oh symmetry for all 3d elements. The intense pre-edge peak for tetrahedral species of 3d transition metals is not due to 1s–3d transition, but transition to the p component in d–p hybridized orbital. The mixing of metal 4p orbitals with the 3d orbitals depends strongly on the coordination symmetry, and the possibility is predictable by group theory. The transition of 1s electron to d orbitals is electric quadrupole component in any of the symmetries. The d–p hybridization does not occur with regular octahedral symmetry, and the weak pre-edge peak consists of 1s–3d electric quadrupole transition. The pre-edge peak intensity for a compound with a tetrahedral center changes as a function of the number of 3d electrons regardless of the kind of element; it is maximized at d0 and gradually decreases to zero at d10. The features of pre-edge peaks in K-edge XANES spectra for 4d elements and the L1-edge for 5d elements are analogous with those for 3d elements, but the pre-edge peak is broadened due to the wide natural width of the core level. Copyright © 2008 John Wiley & Sons, Ltd.

Assignment of pre‐edge peaks in K‐edge x‐ray absorption spectra of 3d transition metal compounds: electric dipole or quadrupole?

(Article begins on next page) Anyone can freely access the full text of works made available as \"Open Access\". Works made available under a Creative Commons license can be used according to the terms and conditions of said license. Use of all other works requires consent of the right holder (author or publisher) if not exempted from copyright protection by the applicable law. Availability: This is the author's manuscript

/pdf/reactivity-of-surface-species-in-heterogeneous-catalysts-1vtf7rqr9y.pdf

Reactivity of Surface Species in Heterogeneous Catalysts Probed by In Situ X-ray Absorption Techniques

The structure of the hydrated gallium(III), indium(III), and chromium(III) ions has been determined in aqueous perchlorate and nitrate solutions by means of the large-angle X-ray scattering (LAXS) and extended X-ray absorption fine structure (EXAFS) techniques. The EXAFS studies have been performed over a wide concentration range, 0.005-1.0 mol.dm(-)(3) (2.6 mol.dm(-)(3) for chromium(III)), while the LAXS studies are restricted to concentrated solutions, ca. 1.5 mol.dm(-)(3). All three metal ions were found to coordinate six water molecules, each of which are hydrogen bonded to two water molecules in a second hydration sphere. The metal-oxygen bond distance in the first hydration sphere of the gallium(III), indium(III), and chromium(III) ions was determined by LAXS and EXAFS methods to be 1.959(6), 2.131(7), and 1.966(8) A. The LAXS data gave mean second sphere M.O distances of 4.05(1), 4.13(1), and 4.08(2) A for the gallium(III), indium(III), and chromium(III) ions, respectively. The perchlorate ion was found to be hydrogen bonded to 4.5(7) water molecules with the O.O distance 3.05(2) A and Cl.O 3.68(3) A. Analyses of the Ga, In, and Cr K-edge EXAFS data of the aqueous perchlorate and nitrate solutions showed no influence on the first shell M-O distance by a change of concentration or anion. The minor contribution from the second sphere M.O distance is obscured by multiple scattering within the tightly bonded first shell. EXAFS data for the alum salts CsM(SO(4))(2).12H(2)O, M = Ga or In, showed the M-O bond length of the hexahydrated gallium(III) and indium(III) ions to be 1.957(2) and 2.122(2) A, respectively.

The Structure of the Hydrated Gallium(III), Indium(III), and Chromium(III) Ions in Aqueous Solution. A Large Angle X-ray Scattering and EXAFS Study.

The long elusive structure of Cu(II) hydrate in aqueous solutions, classically described as a Jahn-Teller distorted octahedron and recently proposed to be a fivefold coordination structure [Pasquarello et al., Science 291, 856 (2001)], has been probed with x-ray-absorption spectroscopy by performing a combined theoretical and experimental analysis. Two absorption channels were needed to obtain a proper reproduction of the x-ray-absorption near-edge structure (XANES) region spectrum, as already observed in other Cu(II) complexes [Chaboy et al., Phys. Rev. B 71, 134208 (2005)]. The extended x-ray-absorption fine-structure (EXAFS) spectrum was analyzed as well within this approach. Quite good reproductions of both XANES and EXAFS spectra were attained for several distorted and undistorted structures previously proposed. Nevertheless, there is not a clearly preferred structure among those including four-, five-, and sixfold coordinated Cu(II) ions. Taking into account our results, as well as many more from several other authors using different techniques, the picture of a distorted octahedron for the Cu(II) hexahydrate in aqueous solution, paradigm of the Jahn-Teller effect, is no longer supported. In solution a dynamical view where the different structures exchange among themselves is the picture that better suits the results presented here.

https://digital.csic.es/bitstream/10261/19733/1/GetPDFServlet.pdf

The hydration of Cu2+: Can the Jahn-Teller effect be detected in liquid solution?

Determination of the Second Hydration Shell of Cr3+ and Zn2+ in Aqueous Solutions by Extended X-ray Absorption Fine Structure

This work reports a theoretical study of the x-ray absorption near-edge structure spectra at the Cu $K$ edge in several Cu(II) complexes with $N$-coordinating ligands showing a square-planar arrangement around metal cation. It is shown that single-channel multiple-scattering calculations are not able to reproduce the experimental spectra. The comparison between experimental data and ab initio computations indicates the need of including the contribution of two electronic configurations ($3{d}^{9}$ and $3{d}^{10}L$) to account for a proper description of the final state during the photoabsorption process. The best agreement between theory and experiment is obtained by considering a relative weight of 68% and 32% for the two absorption channels $3{d}^{10}L$ and $3{d}^{9}$, respectively.

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Ab initio x-ray absorption study of copper K-edge XANES spectra in Cu(II) compounds

A model based on the local density approximation and on the multiple-scattering wave method has been used to analyse the experimental XANES spectra of the crystalline materials rutile and anatase. The results presented are close to the best computations that can be achieved for the solid adopting a local density one-electron theory. The effect of cluster size on the computations has been analysed in the case of rutile concluding that at least 51 atoms are needed to get all the spectral features. Convergence is obtained for a model comprising 75 atoms. The agreement between the theoretical and the experimental spectra is very good even for the pre-edge structures, the origin of which has been the object of controversy. Minor differences, which could be assigned to many-body effects, have been pointed out. SCF X alpha computations have also been performed and allow the formulation of some hypotheses concerning two-electron excitations in the XANES spectra.

http://iopscience.iop.org/article/10.1088/0953-8984/3/45/019/pdf

Adela Muñoz-Páez

Papers

The Structure of the Hydrated Gallium(III), Indium(III), and Chromium(III) Ions in Aqueous Solution. A Large Angle X-ray Scattering and EXAFS Study.

The hydration of Cu2+: Can the Jahn-Teller effect be detected in liquid solution?

Determination of the Second Hydration Shell of Cr3+ and Zn2+ in Aqueous Solutions by Extended X-ray Absorption Fine Structure

Ab initio x-ray absorption study of copper K-edge XANES spectra in Cu(II) compounds

A theoretical study of the XANES spectra of rutile and anatase