6.1.2. Aqueous V(III) Chemistry 877 6.1.3. Oxidation State of Vanadium in Tunicates 878 6.1.4. Uptake of Vanadate into Tunicates 879 6.1.5. Vanadium Binding Proteins: Vanabins 879 6.1.6. Model Complexes and Their Chemistry 880 6.1.7. Catechol-Based Model Chemistry 880 6.1.8. Vanadium Sulfate Complexes 881 6.2. Fan Worm Pseudopotamilla occelata 883 7. Vanadium Nitrogenase 883 7.1. Nitrogenases 883 7.2. Biochemistry of Nitrogenase 884 7.3. Clusters in Nitrogenase and Model Systems: Structure and Reactivity 885

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The chemistry and biochemistry of vanadium and the biological activities exerted by vanadium compounds.

Despite the worldwide public health impact of malaria, neither the mechanism by which the Plasmodium parasite detoxifies and sequesters haem, nor the action of current antimalarial drugs is well understood. The haem groups released from the digestion of the haemoglobin of infected red blood cells are aggregated into an insoluble material called haemozoin or malaria pigment. Synthetic beta-haematin (FeIII-protoporphyrin-IX)2 is chemically, spectroscopically and crystallographically identical to haemozoin and is believed to consist of strands of FeIII-porphyrin units, linked into a polymer by propionate oxygen-iron bonds. Here we report the crystal structure of beta-haematin determined using simulated annealing techniques to analyse powder diffraction data obtained with synchrotron radiation. The molecules are linked into dimers through reciprocal iron-carboxylate bonds to one of the propionic side chains of each porphyrin, and the dimers form chains linked by hydrogen bonds in the crystal. This result has implications for understanding the action of current antimalarial drugs and possibly for the design of new therapeutic agents.

The structure of malaria pigment β-haematin

Molecular materials are characterized by being made up by discrete molecules. This structural property gives in principle many possibilities, to modulate the bulk electrical, magnetic, and optical properties of the material by choosing appropriately the constituent molecules. At the same time, however, it is a challenge to develop synthetic strategies that allow the control of the spatial distribution of the molecules in the lattice. In fact, the bulk properties are always determined by cooperative interactions between the constituent molecules, which consequently must be assembled in the lattice in such a way as to maximize the bulk response. In this Account we provide a concise resume of magnetic phenomena, report briefly on the different strategies that have been developed up to the moment for designing molecular magnetic materials, and then summarize our own approach and the main results that have been obtained in this area.

Toward molecular magnets: The metal-radical approach

Update 1 of: Synthesis and Functionalization of Indoles Through Palladium-Catalyzed Reactions

Carboranes: A New Class of Weakly Coordinating Anions for Strong Electrophiles, Oxidants, and Superacids

Information pertaining to the stereochemistry of metalloporphyrins and other tetrapyrroles continues to expand. The present article reviews important developments of this structural chemistry. Detailed updates on the relationship of the structure and physical properties of iron derivatives are given. Metalloporphyrins with unusually high or low oxidation states are reviewed. Surveys of recent work on π-cation radical complexes, bound O2 species, tetrapyrroles with N-substituents, the stereochemistry of ring-reduced tetrapyrroles and a variety of novel species are given. Newly developed data concerning experimental electron density studies are summarized. Detailed reviews of porphyrin-porphyrin (π-π) interactions in the solid state are given. A variety of important conformational aspects of metalloporphyrins and their consequent results on physical properties are presented. Finally, a number of isomorphous series and crystal packing effects in tetrapyrroles have been detailed.

Recent advances in the stereochemistry of metallotetrapyrroles

.eta.1-Benzene coordination: the synthesis and x-ray crystal structure of a novel silver salt of the weakly coordinating carborane anion B11CH12-

Silver salt metathesis reactions using the very weakly nucleophilic anion B 11 CH 12 − reveal several unexpected features of this otherwise familiar reaction. In contrast to AgClO 4 , which undergoes rapid metathesis with IrCl(CO)(PPh 3 ) 2 , the silver carborane salt Ag(B 11 CH 12 ) forms a very stable adduct. This work shows that the role of the counterion to silver is much more important to the mechanism and outcome of silver halide abstraction reactions

Observations on silver salt metathesis reactions with very weakly coordinating anions

Preparation, structure cristalline par technique de diffraction de rayons X des complexes cites dans le titre

Preparation and structural characterization of nitrosyl complexes of ferric porphyrinates. Molecular structure of aquonitrosyl(meso-tetraphenylporphinato)iron(III)perchlorate and nitrosyl(octaethylporphinato)iron(III)perchlorate

The magnetic interactions between metal and ligand spins in metalloporphyrin ..pi..-cation radicals have been investigated as a function of d orbital type for synthetically accessible S = 1/2 metals from the first transition series. Most instructive is the case of copper(II) where the presumably planar (Cu(TMP)/sup ./))/sup +/ (TMP/sup ./ = ..pi..-cation radical of tetramesitylporphyrinate) has an overall S = 1 state (..mu../sub eff/ = 2.99 ..mu../sub B/). The ferromagnetic coupling of spins is rationalized as arising from the exchange interaction of unpaired electrons in orthogonal magnetic orbitals. By contrast, (Cu(TPP/sup ./))/sup +/ has a ruffled porphyrin core in the solid state and is diamagnetic (S = 0). The antiferromagnetic coupling is rationalized in terms of overlap of the magnetic orbitals, i.e., bond formation with spin pairing in the bonding molecular orbital. The crystal and molecular structure of (Cu(TPP/sup ./))(SbCl/sub 6/) has been determined. The structure consists of (Cu(TPP/sup ./))/sup +/ ions that interact in pairs in the crystalline lattice. Dimer formation is believed to be the cause of the exceptionally small dihedral angles between the peripheral phenyl rings and the porphinato core (average value 41.5/sup 0/). This dimerization is also responsible for the unusual saddle-shaped core conformation. This confirmationmore » has also been observed in other ..pi..-cation radical species. The observed Cu-N bond distance of 1.988 (4) A is typical of that for copper(II) and confirms the ring-oxidized nature of the compound. Crystal data: a = 13.484 (2) A, b = 13.924 (3) A, c = 12.886 (2) A, ..cap alpha.. = 98.90 (2)/sup 0/, ..beta.. = 111.08 (1)/sup 0/, ..gamma.. = 106.97 (2)/sup 0/, triclinic, P1, Z = 2, CuN/sub 4/C/sub 44/H/sub 28/SbCl/sub 6/.« less

Young Ja Lee

Papers

Recent advances in the stereochemistry of metallotetrapyrroles

.eta.1-Benzene coordination: the synthesis and x-ray crystal structure of a novel silver salt of the weakly coordinating carborane anion B11CH12-

Observations on silver salt metathesis reactions with very weakly coordinating anions

Preparation and structural characterization of nitrosyl complexes of ferric porphyrinates. Molecular structure of aquonitrosyl(meso-tetraphenylporphinato)iron(III)perchlorate and nitrosyl(octaethylporphinato)iron(III)perchlorate

Spin coupling in metalloporphyrin. pi. -cation radicals