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

The increase in atmospheric carbon dioxide is linked to climate changes; hence there is an urgent need to reduce the accumulation of CO2 in the atmosphere. The utilization of CO2 as a raw material in the synthesis of chemicals and liquid energy carriers offers a way to mitigate the increasing CO2 buildup. This review covers six important CO2 transformations namely: chemical transformations, photochemical reductions, chemical and electrochemical reductions, biological conversions, reforming and inorganic transformations. Furthermore, the vast research area of carbon capture and storage is reviewed briefly. This review is intended as an introduction to CO2, its synthetic reactions and their possible role in future CO2 mitigation schemes that has to match the scale of man-made CO2 in the atmosphere, which rapidly approaches 1 teraton.

The teraton challenge. A review of fixation and transformation of carbon dioxide

The need to reduce the accumulation of CO2 into the atmosphere requires new technologies able to reduce the CO2 emission. The utilization of CO2 as a building block may represent an interesting approach to synthetic methodologies less intensive in carbon and energy. In this paper the general properties of carbon dioxide and its interaction with metal centres is first considered. The potential of carbon dioxide as a raw material in the synthesis of chemicals such as carboxylates, carbonates, carbamates is then discussed. The utilization of CO2 as source of carbon for the synthesis of fuels or other C1 molecules such as formic acid and methanol is also described and the conditions for its implementation are outlined. A comparison of chemical and biotechnological conversion routes of CO2 is made and the barriers to their exploitation are highlighted.

Utilisation of CO2 as a chemical feedstock: opportunities and challenges

International Tables for X-Ray Crystallography (Published for the International Union of Crystallography.) Vol. 1: Symmetry Groups. Edited by Norman F. M. Henry and Kathleen Lonsdale. Pp. xi + 558. (Birmingham: Kynoch Press, 1952.) 105s.

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International Tables for X-Ray Crystallography

The possibility of recycling CO{sub 2} from industrial emissions and of removing some of this greenhouse gas, an environmental pollutant, is receiving increased attention. Also, the possibility of using CO{sub 2} as the starting material for the synthesis of fine chemicals provides an attractive alternative to compounds presently derived from petroleum. Efforts to convert CO{sub 2} to useful chemicals will inevitably center on transition metal catalysts. Furthermore, efforts to enhance the yield of hydrogen in water gas shift reactions are also centered on carbon dioxide interactions with transition metal catalysts. For all these reasons, a broader understanding of the organometallic chemistry of CO{sub 2} is being sought. In this article, only those compounds that can be clearly identified as having carbon dioxide bound to metal centers through carbon will be considered. Thus the discussions will not include metal formate complexes whose chemistry has been reviewed recently. Also, the discussions will not include metallocarboxylic acids or metallocarboxylate esters except where these compounds have been used as reagents for the synthesis of CO{sub 2} complexes or result from reactions of these compounds. 111 refs.

The Organometallic Chemistry of Carbon Dioxide.

Ulosantoin (2), a phosphorylated hydantoin, has been isolated from organic soluble extracts of the sponge Ulosa ruetzleri and found to exhibit marked insecticidal activity against tobacco hornworm larvae and cockroaches. The structure was determined by X-ray diffraction analysis. A structurally related compound, dimethyl N 2 -creatininylphosphate (1), was also isolated from the sponge extracts, but was inactive in the insecticidal screens

Ulosantoin, a potent insecticide from the sponge Ulosa ruetzleri

The chiral Lewis acid [(η 5 -C 5 H 5 )Re(NO)(PPh 3 )] + serves as an effective template for the stereoselective binding and reduction of methyl ketones. The mechanism of asymmetric induction entails (1) formation of a σ complex with the rhenium cis to the smaller methyl substituent and (2) hydride attack upon a rhenium-oxygen conformer in which the bulky PPh 3 ligand blocks one C=O face of the ketone ligand. Stereoselectivities match or exceed those obtained with other chiral hydride reductants. The alkoxide ligands in the reduction products can be converted to a variety of chiral, optically active organic products. Many of these reactions give optically active rhenium-containing products. Hence, the chiral auxiliary can be recycled without additional optical resolution

Selective activation of one methyl ketone enantioface via .sigma.-binding to a chiral transition-metal template: synthesis, structure, and reactivity of rhenium ketone complexes [(.eta.5-C5H5)Re(NO)(PPh3)(.eta.1-O:C(CH3)R)]+X-

The synthesis of the rhenium/main-group-metal bridging CO/sub 2/ or carboxylate complexes of the formula (eta/sup 5/-C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)(CO/sub 2/ML/sub n/) where M = Li, K, Ge, Sn, or Pb from the rhenium carboxylic acid (eta/sup 5/-C/sub 5/H/sub 5/)Re(NO)(PPh/sub 3/)(COOH) is reported. The molecular structure of the complexes was investigated, and both monodentate and bidentate carboxylate binding modes were observed with the symmetrical bidentate binding in the tin complex being unprecedented. Clean thermal decarboxylation occurs when the main-group metal is tin or lead to provide a convenient route to the preparation of heterobimetallic complexes. 14 references, 1 figure.

Synthesis, structure, and reactivity of transition metal/main group metal bridging carboxylate complexes of the formula (.eta.5-C5H5)Re(NO)(PPh3)(CO2MLn) (M = Li, K, Ge, Sn, Pb)

Reactions of diazomethane derivatives with platinum(II): a facile method for platinum ylide preparation

The reaction of K 2 Pt(NO 2 ) 4 with dilute sulfuric acid has been investigated. At least two polynuclear complexes are formed in the reaction. The first, K 2 [Pt 2 (NO 2 ) 4 (OH) 2 ]•11/2H 2 O, is a hydroxo-bridged dimer of Pt(II). Crystal data are space group Ibca, a=11.879 (6) A, b=13.094 (4) A, c=32.060 (11) A, α=β=γ=90 o , V=4987 (4) A 3 , Z=16, R=0.065, and R w =0.058. The second, K 5 [Pt 4 (NO 2 ) 9 O 3 ]•3H 2 O, is a mixed-valence tetranuclear complex with a trinitritoplatinate (IV) unit oxo bridged to three cyclo-(μ-oxo) dinitritoplatinate (II) units. Crystal data are space group P1, a=9.940 (2) A, b=10.069 (2) A, c=15.206 (3) A, α=72.15 (1) o , γ=72.24 (1) o , V=1354.9 (4) A 3 , Z=2, R=0.032, and R w =0.032

Synthesis and crystal and molecular structures of potassium bis(.mu.-hydroxo)bis[dinitritoplatinate(II)] sesquihydrate and potassium cyclo-tris(.mu.3-oxo-1:2:4;1:3:4;2:3:4)tris[dinitritoplatinate(II)]trinitritoplatinate(IV) trihydrate

Raymond D. Larsen

Papers

Ulosantoin, a potent insecticide from the sponge Ulosa ruetzleri

Selective activation of one methyl ketone enantioface via .sigma.-binding to a chiral transition-metal template: synthesis, structure, and reactivity of rhenium ketone complexes [(.eta.5-C5H5)Re(NO)(PPh3)(.eta.1-O:C(CH3)R)]+X-

Synthesis, structure, and reactivity of transition metal/main group metal bridging carboxylate complexes of the formula (.eta.5-C5H5)Re(NO)(PPh3)(CO2MLn) (M = Li, K, Ge, Sn, Pb)

Reactions of diazomethane derivatives with platinum(II): a facile method for platinum ylide preparation

Synthesis and crystal and molecular structures of potassium bis(.mu.-hydroxo)bis[dinitritoplatinate(II)] sesquihydrate and potassium cyclo-tris(.mu.3-oxo-1:2:4;1:3:4;2:3:4)tris[dinitritoplatinate(II)]trinitritoplatinate(IV) trihydrate