Oxidative demetalation of cyclohexadienyl ruthenium(II) complexes: a net Ru-mediated dearomatization

[reaction: see text] An experimentally simple method for the demetalation of spirocyclic cyclohexadienylruthenium(II) complexes has been developed. Treatment of an alkoxy-substituted cyclohexadienyl complex with CuCl(2) affords either azaspiro[4.5]decane derivatives or heavily functionalized tetrahydroisoquinolines. The former reaction manifold completes a net Ru-mediated dearomatization as the organometallic starting materials are prepared from (eta(6)-arene)Ru(II) precursors. Both of these heterocyclic products are well suited for further synthetic elaboration.     

Stability and Structure of Activated Macrocycles. Ligands with Biological Applications

Single p-toluic acid pendant groups were attached to 1,4,7,10,13-pentaazacyclopentadecane (15aneN5) and 1,4,8,11-tetraazacyclotetradecane (cyclam) to prepare bifunctional reagents for radiolabeling monoclonal antibodies with (64,67)Cu. The ligands are 1,4,7,10,13-pentaazacyclopentadecane-1-(alpha-1,4-toluic acid) (PCBA) and 1,4,8,11-tetraazacyclotetradecane-1-(alpha-1,4-toluic acid) (CPTA). For the parent macrocycles and their pendant arm derivatives, the 1:1 Cu(2+) complexes dissociate only below pH 2. At pH 0.0 and 25 degrees C the CPTA-Cu complex has a half-life toward complete dissociation of 24 days. A new approach was developed for the estimation of the Cu(2+) stability constant for the kinetically robust CPTA. All other formation constants were determined at 25.0 degrees C with batch spectrophotometric techniques. Potentiometric titrations were used to determine the protonation constants of the macrocyclic ligands as well as of the metal chelates. The protonation constants, stability constants, and pM's are discussed in terms of both molecular mechanics calculations and the ligands' potential applicability as copper(II) radiopharmaceuticals.     

Structure of New 2-Oxo-2,8-dihydro-[l,2,4]oxadiazolo-[2,3-a]pyrimidinecarbamates

The structure of new 2-oxo-2,8-dihydro-[l,2,4]oxadiazolo-[2,3-a]pyrimidine-carbamates 1 was established by correlating the IR. and NMR. data with these of analogous compounds. A X-ray crystallographic analysis of 1c gave an unequivocal proof of structural assignment.     

Synthesis,Structure, and Stability of Cs4ZrO4

The colorless Cs₄ZrO₄ is obtained from the reaction of stoichiometric proportions of Cs, CsO₂, and finely divided ZrO₂ in a sealed Ag container at 400–650°C for several days. Regrinding and re-reaction provide a single phase sample. The compound is monoclinic (P2₁/c, Z = 4, a = 7.172 (1) Å, b = 19.907 (1) Å, c = 7.157 (1) Å, β = 113.1 (1)Å, R = 0.032) and isostructural with Cs₄PbO₄, with isolated ZrO₄^4? tetrahedra (d(Zr–O) = 1.97 Å). The compound decomposes to Cs₂ZrO₃ (a) in the presence of excess oxygen or CsO₂, (b) in high vacuum near 275°C, or (c) in a sealed container at about 730 ± 10°C.     

Magnetic nanoparticle assemblies on denatured DNA show unusual magnetic relaxivity and potential applications for MRI

Denatured (substantially single-stranded) herring sperm DNA acts as a template for the preparation of magnetic nanowires, forming stable aqueous suspensions, which exhibit unprecedentedly high relaxivity at low field, suggesting that the material may be a potentially useful reagent for MRI.     

Carbon nanohorns grown from ruthenium nanoparticles

A nanoscale ruthenium/gold bimetallic cluster of clusters has been used as a molecular precursor to produce pure ruthenium nanoparticles (seeds) as catalysts for the growth of carbon nanohorns (CNHs).     

Evaluation of the immobilized artificial membrane phosphatidylcholine: Drug discovery column for high-performance liquid chromatographic screening of drug–membrane interactions

Chromatographic retention factors (k′) of a series of eight β-adrenoceptor antagonist compounds (β-adrenolytic drugs) were determined employing an immobilized artificial membrane column (IAM.PC.DD). The influence of mobile phase pH, ionic strength, and organic modifier composition was studied in order to examine column performance. After the IAM.PC.DD columns were exposed to approximately 7000 column volumes of a 0.01 M PBS mobile phase, five out of six columns tested showed significant peak broadening and decreased k′ values indicative of premature column failure. The data suggested that the immobilized phospholipids stationary phase was removed by the 0.01 M PBS mobile phase. The β-adrenolytic drug's log k′_IAM values obtained with an IAM.PC.DD column were compared to an ^esterIAM.PC.MG column for predicting drug membrane interactions. For the linear regression analysis between log k′_IAM and the logarithm of the n-octanol–water partition coefficients (r_IAM.PC.DD=0.8710 vs. r_IAM.PC.MG=0.9538), the C₁₈ HPLC retention factors (r_IAM.PC.DD=0.8408 vs. r_IAM.PC.MG=0.9380), the liposome partition coefficients (r_IAM.PC.DD=0.8887 vs. r_IAM.PC.MG=0.9187), and various pharmacokinetic parameters, significantly better correlations were obtained with the ^esterIAM.PC.MG column than the IAM.PC.DD column.     

The co-stacking of a planar metal complex and a novel 1,3-dithiole: The synthesis and crystal structure of [Pt(mnt)(CNMe)2]·(NC)2C2S2

The reaction of [NBu₄ⁿ]2Cu(mnt)₂] with [Pt(CNMe)₄][PF₆]₂ gives [Pt(mnt)(CNMe)₂]·(NC)₂C₂S₂CNMe, an X-ray study of which reveals co-stacking of neutral planar metal and organic molecules.     

X-ray mapping in electron-beam instruments.

This review traces the development of X-ray mapping from its beginning 50 years ago through current analysis procedures that can reveal otherwise obscure elemental distributions and associations. X-ray mapping or compositional imaging of elemental distributions is one of the major capabilities of electron beam microanalysis because it frees the operator from the necessity of making decisions about which image features contain elements of interest. Elements in unexpected locations, or in unexpected association with other elements, may be found easily without operator bias as to where to locate the electron probe for data collection. X-ray mapping in the SEM or EPMA may be applied to bulk specimens at a spatial resolution of about 1 microm. X-ray mapping of thin specimens in the TEM or STEM may be accomplished at a spatial resolution ranging from 2 to 100 nm, depending on specimen thickness and the microscope. Although mapping has traditionally been considered a qualitative technique, recent developments demonstrate the quantitative capabilities of X-ray mapping techniques. Moreover, the long-desired ability to collect and store an entire spectrum at every pixel is now a reality, and methods for mining these data are rapidly being developed.     

Reactions of dimethyldivinylsilane,dimethyldivinyltin and allyltrimethyltin with diethylene (tertiary) phosphine)platinum complexes

The compounds [Pt(C₂H₄)₂(PR₃)] [PR₃ = P-tBu₂Me, P(C₆H₁₁)₃, PPh₃] react dimethyldivinylsilane or dimethyldivinyltin to give chelate complexes [Pt{(CH₂CH)₂MMe₂} (PR₃)] (M = Si or Sn). allyltrimethyltin reacts with various diethylene (tertiary phosphine)platinum compounds with cleavage of the allyl group to afford complexes [Pt(SnMe₃)(η³-C₃H₅)(PR₂)]. The NMR spectra (¹³C, ¹H and ³¹P) of the new compounds have been recorded, and the data are discussed in terms of the structures proposed.