The interaction of silver(II) complexes with biological macromolecules and antioxidants.

Silver is widely used for its antimicrobial properties, but microbial resistance to heavy metals is increasing. Silver(II) compounds are more oxidizing and therefore have the potential to overcome resistance via extensive attack on cellular components, but have traditionally been hard to stabilize for biological applications. Here, the high oxidation state cation was stabilised using pyridinecarboxylate ligands, of which the 2,6-dicarboxypyridine Ag(II) complex (Ag2,6P) was found to have the best tractability.

The stability of mercaptobenzothiazole based soft scorpionate complexes.

The chemistry of the hydrotris(mercaptobenzothiazolyl)borate anion (Tbz) with metal salts (HgI2, SbI3, BiI3, CoCl2) is reported in an attempt to probe the stability of the of Tbz ligand once coordinated to hard and soft metals. Complexes of Tbz with bismuth, containing the [Bi(Tbz)I3](-) anion, are stable, but with the other metals this is not the case. Although simple complexes such as [Hg(Tbz)I] and [E(Tbz)I3](-) (E = Sb, Bi) can be isolated from the reaction mixtures, subsequent reactions lead to ligand modification or decomposition.

Soft scorpionate coordination at alkali metals.

Reported here are the single-crystal X-ray structure analyses of bis-μ-methanol-κ(4)O:O-bis{[hydrotris(3-phenyl-2-sulfanylidene-2,3-dihydro-1H-1,3-imidazol-1-yl)borato-κ(3)H,S,S'](methanol-κO)sodium(I)}, [Na2(C27H22BN6S3)2(CH4O)4] (NaTm(Ph)), bis-μ-methanol-κ(4)O:O-bis{[hydrotris(3-isopropyl-2-sulfanylidene-2,3-dihydro-1H-1,3-imidazol-1-yl)borato-κ(3)H,S,S'](methanol-κO)sodium(I)}-diethyl ether-methanol (1/0.3333/0.0833), [Na2(C18H28BN6S3)2(CH4O)4]·0.

Soft scorpionate anions as platforms for novel heterocycles.

Soft scorpionates have thus far been seen mainly as a family of ligands. Their chemistry is extended here to the production of novel cationic macrocycles using dihaloalkanes. By replacing the dihaloalkanes with mild oxidising agents (NO(+), I2) we obtain two unique polycyclic heterocycles.

S-alkylation of soft scorpionates.

The alkylation reactions of soft scorpionates are reported. The hydrotris(S-alkyl-methimazolyl)borate dications (alkyl = methyl, allyl, benzyl), which were prepared by the reaction of Tm(Me) anion and primary alkyl halides, have been isolated and structurally characterised. The reaction is, however, not universally successful.

Tungsten(VI) N-Heterocyclic Carbene Complexes: Synthetic, Structural, and Computational Study.

The reaction of WOCl with 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene (Idipp) leads to an orange solid whose spectroscopic data are consistent with the 1:1 adduct [WOCl(Idipp)]. Computational studies at the DFT level further support this formulation. Exposure of this compound to the atmosphere results in rapid hydrolysis to various imidazolium salts.

Reductions of challenging organic substrates by a nickel complex of a noninnocent crown carbene ligand.

The first crown-tetracarbene complex of Ni(II) has been prepared, and its crystal structure determined. The complex can be reduced by Na/Hg, with an uptake of two electrons. The reduced complex reductively cleaves arenesulfonamides, including those derived from secondary aliphatic amines, and effects Birch reduction of anthracenes as well as reductive cleavage of stilbene oxides.

Surface science of soft scorpionates.

The chemisorption of the soft scorpionate Li[PhTm(Me)] onto silver and gold surfaces is reported. Surface enhanced Raman spectroscopy in combination with the Raman analysis of suitable structural models, namely, [Cu(kappa(3)-S,S,S-PhTm(Me))(PCy(3))], [Ag(kappa(3)-S,S,S-PhTm(Me))(PCy(3))], [Ag(kappa(2)-S,S-PhTm(Me))(PEt(3))], and [Au(kappa(1)-S-PhTm(Me))(PCy(3))], are employed to identify the manner in which this potentially tridentate ligand binds to these surfaces. On colloidal silver surface-enhanced Raman spectroscopy (SERS) spectra are consistent with PhTm(Me) binding in a didentate fashion to the surface, holding the aryl group in close proximity to the surface.

Enhanced hydrogen storage in Ni/Ce composite oxides.

The properties of dried (but not calcined) coprecipitated nickel ceria systems have been investigated in terms of their hydrogen emission characteristics following activation in hydrogen. XRD and BET data obtained on the powders show similarities to calcined ceria but it is likely that the majority of the material produced by the coprecipitation process is largely of an amorphous nature. XPS data indicate very little nickel is present on the outermost surface of the particles.

A coordination polymer strategy for anion encapsulation: anion-pi interactions in (4,4) nets formed from Ag(I) salts and a flexible pyrimidine ligand.

Anions encapsulated by a uniform mode of anion-pi binding in isomorphous (4,4) nets formed from Ag(I) salts and bis(4-pyrimidylmethyl)sulfide appear to be structurally directing.

The first bona-fide sodium complex of hydrotris(methimazolyl)borate: an example of sodium exhibiting a preference for sulfur over oxygen.

The synthesis and structure of two related sodium complexes are reported which demonstrate that sulfur can preferentially complex to sodium irrespective of the presence of more apposite donor species such as DMF.

[Mo(Tm(Me))(O)2Cl]: an alternative functional model of sulfite oxidase.

The hydrotris(methimazolyl)borate anion (TmMe) has been used to synthesize an alternative functional model ([Mo(TmMe)(O)2Cl]) of the metalloenzyme sulfite oxidase. It has been shown that the complex undergoes oxygen atom transfer chemistry and that it performs the primary function of the enzyme, sulfite oxidation. A method using ion chromatography has been developed to definitively prove that sulfite is oxidized to sulfate.

Probing anion-pi interactions in 1-D Co(II), Ni(II), and Cd(II) coordination polymers containing flexible pyrazine ligands.

Two flexible thioether-containing heterocyclic ligands bis(2-pyrazylmethyl)sulfide (L1) and 2-benzylsulfanylmethylpyrazine (L2) have arene rings with differing pi-acidities which were used to probe anion-pi binding in five 1-D coordination polymers formed from the metal salts Co(ClO4)2, Ni(NO3)2, and Cd(NO3)2. In {[Co(L1)(MeCN)2](ClO4)2}infinity (1), {[Ni(L1)(NO3)2]}infinity (2), and {[Cd2(L1)(MeCN)(H2O)(NO3)4].H2O}infinity (3.

Helices versus zigzag chains: one-dimensional coordination polymers of Ag(I) and Bis(4-pyridyl)amine.

Five one-dimensional coordination polymers were prepared by the reaction of a bent bridging ligand, bis(4-pyridyl)amine (bpa), with an extensive series of AgX salts (X = CF3SO3, PF6, ClO4, NO3). The 1D polymer networks formed with AgCF3SO3 (1), AgPF6 (2.MeCN), and AgClO4 (3.

Coinage metal complexes of a boron-substituted soft scorpionate ligand.

An improved synthesis of lithium phenyltris(methimazolyl)borate, Li[PhTm(Me)], (methimazole = 1-methylimidazole-2-thione) is described, and the structure of the methanol-solvated [Li(OHMe)4][PhTm(Me)] has been determined. The syntheses and characterization of complexes [M(PhTm(Me))(PR3)] (M = Cu, Ag, Au; R = Et, Ph;) are reported, and the complexes [Cu(PhTm(Me))(PPh3)], [Ag(PhTm(Me))(PEt3)] and [Au(PhTm(Me))(PEt3)] are crystallographically characterized, showing a progression from pseudo-tetrahedral geometry (copper, S3P coordination) to trigonal planar geometry (silver, S2P coordination) to linear geometry (gold, SP coordination). In addition, the copper(I) and silver(I) triphenylphosphine complexes of the adventitiously formed phenylhydrobis(methimazolyl)borate ligand, [M(PhBm(Me))(PPh3)], have been crystallographically characterized, showing both species to have a trigonal planar primary coordination sphere, with a secondary M.

Lower main-group element complexes with a soft scorpionate ligand: the structural influence of stereochemically active lone pairs.

The syntheses and structures of complexes of the fifth period elements indium and antimony, and the sixth period element bismuth with the soft scorpionate ligand, hydrotris(methimazolyl)borate (Tm(Me)) are reported. A considerable variety of structural motifs were obtained by reaction of the main-group element halide and NaTm(Me). The indium(III) complexes took the form [In(kappa(3)-Tm(Me))(2)](+).

Flexible ligands and structural diversity: isomerism in Cd(NO3)2 coordination polymers.

The ligands 1,4-bis(2-pyridylmethylsulfanylmethyl)benzene (L1) and 2,5-bis(2-pyridylmethylsulfanylmethyl)pyrazine (L2) were treated with Cd(NO3)2.4H2O in metal-to-ligand ratios of 1:1 and 2:1, respectively; L2 was also treated with CdCl2.2.

Cobalt half-sandwich, sandwich, and mixed sandwich complexes with soft tripodal ligands.

Reaction of sodium hydrotris(methimazolyl)borate (NaTm(Me)) with cobalt halides leads to the formation of paramagnetic pseudotetrahedral [Co(Tm(Me))X] (X = Cl, Br, I), of which the bromide has been crystallographically characterized. Mass spectrometry reveals the presence of higher molecular weight fragments [Co(Tm(Me))(2)](+) and [Co(2)(Tm(Me))(2)X](+) in solution. Aerial oxidation in donor solvents (e.

Virtual reality neurosurgery: a simulator blueprint.

Objective: This article details preliminary studies undertaken to integrate the most relevant advancements across multiple disciplines in an effort to construct a highly realistic neurosurgical simulator based on a distributed computer architecture. Techniques based on modified computational modeling paradigms incorporating finite element analysis are presented, as are current and projected efforts directed toward the implementation of a novel bidirectional haptic device.

Methods: Patient-specific data derived from noninvasive magnetic resonance imaging sequences are used to construct a computational model of the surgical region of interest.

Pushing the frontiers of hard and soft scorpionate chemistry.

The preparation and structure of the first scorpionate complex of a group 16 element, [Te(kappa(2)-Tm(Me))(2)], is reported. It displays square planar geometry at the Te atom and two distinct ligand conformations. In addition, the first pyrazolylborate complex of a group 15 element, [Bi(Tp)(2)(pzH)Cl], has been synthesized and characterized.

A monomeric imidazol-2-ylidene-silver(I) chloride complex: synthesis, structure, and solid state 109Ag and 13C CP/MAS NMR characterization.

The structure of 1,3-bis(2,4,6-trimethylphenyl)-imidazol-2-ylidene-silver(I) chloride, 1, has been determined to be a monomer with weak head-to-tail H...

Virtual reality surgery: neurosurgery and the contemporary landscape.

Objective: Virtual reality-simulated environments have been used for the training of personnel, most notably for military applications, for more than 35 years. The advantages conferred by being able to train novice personnel in a low- to no-risk simulated environment have long been appreciated by the medical community. The recent availability of affordable gigahertz-range microprocessors (once the exclusive domain of the Cray supercomputer) has made photorealistic graphical rendering and manipulation of virtual surgical substrates a reality.

A highly stable N-heterocyclic carbene complex of trichloro-oxo-vanadium(V) displaying novel Cl-Ccarbene bonding interactions.

Reaction of 1,3-dimesitylimidazol-2-ylidene and trichloro-oxo-vanadium(V) yields an air stable 1:1 adduct, which demonstrates the utility of N-heterocyclic carbenes to stabilize metal complexes in high oxidation states. The molecular structure of this compound reveals that the chloride ligands cis to the carbene are oriented toward the Ccarbene atom. Density functional theory calculations show that a bonding interaction occurs between lone pairs of these chlorides and the formally unoccupied p-orbital of the carbene.

The genesis of neurosurgery and the evolution of the neurosurgical operative environment: part II--concepts for future development, 2003 and beyond.

The future development of the neurosurgical operative environment is driven principally by concurrent development in science and technology. In the new millennium, these developments are taking on a Jules Verne quality, with the ability to construct and manipulate the human organism and its surroundings at the level of atoms and molecules seemingly at hand. Thus, an examination of currents in technology advancement from the neurosurgical perspective can provide insight into the evolution of the neurosurgical operative environment.